How to search for channels

Abstract

Provided is a channel search method for searching a plurality of physical channels of OFDM digital broadcasting, the method comprising: when the physical channels each can include both or either one of a first broadcast signal and a second broadcast signal that have different ways of error correction processing, performing a first channel search relating to the first broadcast signal on the physical channels; during the first channel search, determining physical channels to be searched of a second channel search relating to the second broadcast signal; and performing the second channel search on the physical channels to be searched of the second channel search.

Description

[Technical Field]

[0001] The present disclosure relates to a channel search method for searching for physical channels of digital broadcasting. By law Regarding. [Background technology]

[0002] In recent years, next-generation digital broadcasting, which is an advanced version of existing digital broadcasting, has been proposed. Furthermore, when next-generation digital broadcasting begins, it is possible that both existing digital broadcasting and next-generation digital broadcasting will be transmitted, and therefore methods for dealing with this situation have been proposed.

[0003] One such method is the three-layer method shown in Non-Patent Document 1. This method divides the hierarchy of physical channels of digital broadcasting based on the existing ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) system into three layers, with one layer dedicated to existing digital broadcasting such as 2K broadcasting and the other layer dedicated to next-generation digital broadcasting such as 4K broadcasting. Another method proposed is the Layered Division Multiplexing (LDM) method shown in Non-Patent Document 2. This method superimposes 4K broadcast signals on the physical channels of 2K broadcasting based on the existing ISDB-T system. Digital broadcasting based on these methods can be realized by adding next-generation digital broadcasting to the physical channels of existing digital broadcasting.

[0004] On the other hand, a new broadcasting system that differs from the ISDB-T system and significantly improves transmission capacity has also been proposed, as shown in Non-Patent Document 3. This system can be realized by using a physical channel that differs from that of ISDB-T digital broadcasting.

[0005] Furthermore, as shown in Patent Document 1, a technique for transmitting various information using TMCC (Transmission Multiplexing Configuration Control) information of the ISDB-T system is also disclosed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-96343 [Non-patent literature]

[0007] [Non-Patent Document 1] "Three-layer segmentation method (MIMO / SISO)" for transmitting terrestrial digital broadcasting and 4K broadcasting in a 6MHz band, Ministry of Internal Affairs and Communications, Information and Communications Council, Broadcasting System Committee, May 18, 2020, Kansai Telecasting, [Retrieved December 28, 2021], Internet<URL:https: / / www.soumu.go.jp / main_content / 000693904.pdf> [Non-patent document 2] "Results of the Ministry of Internal Affairs and Communications Project on the Enhancement of Terrestrial Digital Television Systems - Study on Enhancement of Terrestrial Digital Broadcasting Using LDM Technology" Information and Communications Council, Information and Communications Technology Subcommittee, 73rd Broadcasting System Committee Materials, Media Planning Office, May 18, 2020, TBS, [Retrieved December 28, 2021], Internet<URL:https: / / www.soumu.go.jp / main_content / 000693903.pdf> [Non-patent document 3] "Experimental Methods for Advanced Terrestrial Broadcasting," Broadcasting System Committee Document 73-6, May 18, 2020, Japan Broadcasting Corporation, [Retrieved December 28, 2021], Internet<URL:https: / / www.soumu.go.jp / main_content / 000693902.pdf> Summary of the Invention [Problem to be solved by the invention]

[0008] To receive terrestrial digital broadcasts, a channel search is performed to determine which physical channels are receivable at the location where the receiving device is placed, i.e., which broadcasting stations' broadcasts are receivable. For example, a terrestrial digital broadcast receiving device sequentially selects multiple physical channels in the UHF band (e.g., 13CH to 52CH), and registers the physical channels that can be received in the receiving device. This associates the physical channels with display channels (e.g., remote control channels), and the channel search is completed.

[0009] However, when next-generation digital broadcasting begins and both existing and next-generation digital broadcasting are transmitted, it becomes necessary to perform separate channel searches for both existing and next-generation digital broadcasting, which poses the problem of longer search times.

[0010] The present disclosure aims to provide a channel search method and the like that can prevent search time from becoming long when performing channel searches corresponding to multiple digital broadcasts that each use different error correction processing methods. [Means for solving the problem]

[0011] A channel search method in one embodiment of the present disclosure is a channel search method for searching multiple physical channels of digital broadcasting using the OFDM (Orthogonal Frequency Division Multiplexing) method, and when the physical channel can include both a first broadcast signal and a second broadcast signal that have different error correction processing methods, or can include either one of them, includes: performing a first channel search for the first broadcast signal on the physical channel; determining, during the first channel search, the physical channel to be searched for in a second channel search for the second broadcast signal; and performing the second channel search on the physical channel that has been searched for in the second channel search.

[0015] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0016] According to the channel search method and the like of the present disclosure, when performing a channel search corresponding to each of a plurality of digital broadcasts that use different error correction processing methods, it is possible to prevent the search time from becoming long. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of the structure of a physical channel in the three-layer system, the LDM system, and the new broadcasting system. [Figure 2] FIG. 2 is a diagram illustrating a configuration of a receiving device according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating a configuration of a demodulation unit of the receiving device according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing another configuration of the demodulation unit according to the first embodiment. [Figure 5] FIG. 5 is a flowchart showing a channel search method according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing the search results of the first channel search and the physical channels to be searched in the second channel search. [Figure 7] FIG. 7 is a flowchart showing a channel search method according to the first modification of the first embodiment. [Figure 8] FIG. 8 is a flowchart showing a part of a channel search method according to the second modification of the first embodiment. [Figure 9] FIG. 9 is a flowchart showing a channel search method according to the third modification of the first embodiment. [Figure 10] FIG. 10 is a flowchart showing a part of a channel search method according to the fourth modification of the first embodiment. [Figure 11] FIG. 11 is a diagram illustrating a configuration of a receiving device according to the second embodiment. [Figure 12] FIG. 12 is a diagram illustrating a configuration of a demodulation unit of a receiving device according to the second embodiment. [Figure 13] FIG. 13 is a flowchart showing a channel search method according to the second embodiment. [Figure 14] FIG. 14 is a diagram showing the search results of the first channel search and the physical channels to be searched in the second channel search. [Figure 15] FIG. 15 is a flowchart showing a channel search method according to the first modification of the second embodiment. [Figure 16] FIG. 16 is a diagram illustrating a configuration of a receiving device according to the third embodiment. [Figure 17] FIG. 17 is a diagram illustrating a configuration of a demodulation unit of a receiving device according to the third embodiment. [Figure 18] FIG. 18 is a flowchart showing a channel search method according to the third embodiment. [Figure 19]FIG. 19 is a flowchart showing a part of a channel search method according to the first modification of the third embodiment. [Figure 20] FIG. 20 is a flowchart showing a channel search method according to the second modification of the third embodiment. [Figure 21] FIG. 21 is a flowchart showing a part of a channel search method according to the third modification of the third embodiment. [Figure 22] FIG. 22 is a diagram illustrating a configuration of a receiving device according to the fourth embodiment. [Figure 23] FIG. 23 is a flowchart showing a channel search method according to the fourth embodiment. [Figure 24] FIG. 24 is a flowchart showing a channel search method according to the first modification of the fourth embodiment. [Figure 25] FIG. 25 is a flowchart showing a channel search method according to the second modification of the fourth embodiment. [Figure 26] FIG. 26 is a diagram illustrating a configuration of a receiving device according to the fifth embodiment. [Figure 27] FIG. 27 is a flowchart showing a channel search method according to the fifth embodiment. [Figure 28] FIG. 28 is a flowchart showing a channel search method according to the first modification of the fifth embodiment. [Figure 29] FIG. 29 is a diagram illustrating a configuration of a receiving device according to the sixth embodiment. [Figure 30] FIG. 30 is a diagram illustrating a configuration of a demodulation unit of a receiving device according to the sixth embodiment. [Figure 31] FIG. 31 is a diagram showing another configuration of the demodulation unit according to the sixth embodiment. [Figure 32A] FIG. 32A is a flowchart showing a part of a channel search method according to the sixth embodiment. [Figure 32B] FIG. 32B is a flowchart showing another part of the channel search method according to the sixth embodiment. [Figure 33A]FIG. 33A is a flowchart showing a part of a channel search method according to the first modification of the sixth embodiment. [Figure 33B] FIG. 33B is a flowchart showing another part of the channel search method according to the first modification of the sixth embodiment. [Figure 34A] FIG. 34A is a flowchart showing a part of a channel search method according to the second modification of the sixth embodiment. [Figure 34B] FIG. 34B is a flowchart showing another part of the channel search method according to the second modification of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] The channel search method of the present disclosure is a method for searching multiple physical channels of digital broadcasting, where a physical channel can contain two broadcast signals with different error correction processing methods, or can contain any one broadcast signal.

[0019] In the following, when the resolution of high-definition broadcasting is K, the image resolution of each broadcast will be referred to as 2K, 4K, 8K, etc. For simplicity, the explanation will be given assuming that existing digital broadcasting is 2K broadcasting and next-generation digital broadcasting is 4K broadcasting. In reality, next-generation digital broadcasting is not limited to 4K broadcasting and may also be 8K broadcasting.

[0020] Existing digital broadcasts are transmitted using multiple physical channels in the UHF band. Physical channels are assigned to each broadcasting station, and in Japan they are channels 13 to 52 on the UHF band that transmits terrestrial digital broadcasts. Each physical channel from 13 to 52 is divided into 6 MHz intervals. The ISDB-T (Integrated Services Digital Broadcasting - Terrestrial) standard divides one physical channel, consisting of 13 segments, into three layers, making it possible to transmit different broadcast signals on each of the three layers.

[0021] Simultaneous broadcasting of both existing and next-generation digital broadcasts can be achieved, for example, by the three-layer method described in Non-Patent Document 1, the LDM (Layered Division Multiplexing) method described in Non-Patent Document 2, or the new broadcasting method described in Non-Patent Document 3.

[0022] FIG. 1 is a diagram showing a schematic diagram of the structure of a physical channel in the three-layer system, the LDM system, and the new broadcasting system.

[0023] The three-layer system shown in Figure 1(a) is a technology that transmits one-segment broadcast signals in layer A, which consists of one of the 13 segments in a physical channel, 2K broadcast signals in layer B, which consists of eight segments, and 4K broadcast signals in layer C, which consists of four segments. The LDM system shown in Figure 1(b) is a technology that applies LDM technology to transmit 4K broadcast signals superimposed on 2K broadcast signals. The new broadcast system shown in Figure 1(c) is a different system from ISDB-T, and is a technology that transmits signals using physical channels other than the 2K broadcast channels among channels 13 to 52.

[0024] Below, examples of channel searches when existing and next-generation digital broadcasts are transmitted using a three-layer system or an LDM system using the ISDB-T system are shown in embodiments 1 and 4. Also, examples of channel searches when existing digital broadcasts are transmitted using the ISDB-T system and next-generation digital broadcasts are transmitted using a new broadcasting system are shown in embodiments 2, 3 and 5. Also, examples of channel searches when existing and next-generation digital broadcasts are transmitted using a three-layer system, an LDM system and a new broadcasting system are shown in embodiment 6.

[0025] Hereinafter, embodiments will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in an independent claim showing an implementation form of one aspect of the present disclosure will be described as optional components. Implementation forms of the present disclosure are not limited to the current independent claim, but may also be expressed by other independent claims.

[0026] It should be noted that the drawings are schematic diagrams and are not necessarily strict illustrations. In addition, in the drawings, substantially the same components are denoted by the same reference numerals, and duplicated explanations may be omitted or simplified.

[0027] (Embodiment 1) [1-1. Configuration of receiving device] The following describes the configuration of a receiving device according to embodiment 1. The receiving device according to embodiment 1 receives 2K broadcast signals and 4K broadcast signals transmitted by the ISDB-T system, and searches a plurality of physical channels of these digital broadcasts.

[0028] FIG. 2 is a diagram showing a configuration of the receiving device 1 according to the first embodiment.

[0029] As shown in Fig. 2, the receiving device 1 includes a tuner unit 10, a demodulator unit 20, a decoder unit 40, a controller 50, and a display unit 70. The controller 50 includes a memory unit 60. Fig. 2 also shows an antenna 2 connected to the receiving device 1. The antenna 2 may be built into the receiving device 1. The tuner unit 10, the demodulator unit 20, the decoder unit 40, and the controller 50 may be partially or entirely integrated, or some functions may be included in other functions.

[0030] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and controls the tuner unit 10. The control unit 50 also outputs a channel selection instruction signal and a setting signal to the demodulation unit 20 and the decoding unit 40, respectively, and controls the demodulation unit 20 and the decoding unit 40, respectively.

[0031] An RF signal is input to the tuner unit 10 from the antenna 2. The tuner unit 10 selects a predetermined physical channel based on a channel selection instruction signal output from the control unit 50, converts the RF signal corresponding to the predetermined physical channel into an IF (Intermediate Frequency) signal, and outputs the IF signal to the demodulation unit 20.

[0032] The demodulation unit 20 performs demodulation processing on the IF signal output from the tuner unit 10. The demodulation unit 20 performs the demodulation processing based on the tuning instruction signal and setting signal output from the control unit 50, and outputs the demodulated signal to the decoding unit 40. The demodulation unit 20 also outputs demodulation information (for example, synchronization information, C / N (carrier to noise ratio) information, error information) and control information obtained by the demodulation processing to the control unit 50. The demodulation unit 20 of this embodiment performs error correction processing corresponding to each of 2K broadcasting and 4K broadcasting, which will be described later.

[0033] The decoding unit 40 performs a decoding process on the signal output from the demodulation unit 20. The decoding unit 40 performs the above-mentioned decoding process based on the channel selection instruction signal and setting signal output from the control unit 50, and outputs the decoded video signal to the display unit 70. The decoding unit 40 also outputs the program information obtained by the decoding process to the control unit 50.

[0034] The display unit 70 is a display device such as a display, etc. The display unit 70 displays an image based on the video signal output from the decoding unit 40.

[0035] Fig. 3 is a diagram showing the configuration of the demodulation unit 20 of the receiving device 1. Fig. 3 shows the demodulation unit 20 that supports a three-layer system.

[0036] As shown in Figure 3, the demodulation unit 20 includes an AD conversion unit 21, a time axis processing unit 22, an FFT unit 23, a carrier synchronization unit 24, an equalization unit 25, a TMCC (Transmission Multiplexing Configuration Control) decoding unit 26, a 4K broadcast control information decoding unit 27, a deinterleaving unit 28, a first error correction processing unit 31, a second error correction processing unit 32, and an output selection unit 33.

[0037] The AD conversion unit 21 outputs the IF signal output from the tuner unit 10 after digital conversion to the time axis processing unit 22 .

[0038] The time axis processing unit 22 converts the IF signal into a baseband signal by orthogonal transforming it based on the signal output from the AD conversion unit 21, and further performs timing synchronization (symbol synchronization) of OFDM (Orthogonal Frequency Division Multiplexing) symbols. The signal processed by the time axis processing unit 22 is output to the FFT unit 23.

[0039] The output signal from the tuner unit 10 may be a baseband signal instead of an IF signal. In this case, orthogonal transform processing in the time axis processing unit 22 is not required. Hereinafter, in this embodiment and other embodiments, only IF signals will be described, but all relevant parts may be replaced with baseband signals, and processing equivalent to the processing in the time axis processing unit 22 will be interpreted appropriately.

[0040] The FFT unit 23 performs FFT processing on the signal output from the time axis processing unit 22 to convert it into a signal on the frequency axis, and outputs the converted signal to the carrier synchronization unit 24.

[0041] The carrier synchronization unit 24 performs carrier position synchronization processing on the signal output from the FFT unit 23, and outputs the synchronized signal to the equalization unit 25, the TMCC decoding unit 26, and the 4K broadcast control information decoding unit 27, respectively.

[0042] The TMCC decoding unit 26 synchronizes the OFDM frame using a synchronization word included in the TMCC signal, using the signal output from the carrier synchronization unit 24. The TMCC decoding unit 26 then outputs synchronization information indicating whether or not synchronization with the selected physical channel has been achieved, and the equalization unit 25, which will be described later, outputs C / N information to the control unit 50.

[0043] The TMCC decoder 26 decodes the signal related to TMCC information, which is one of the control information, among the signals output from the carrier synchronization unit 24. This signal contains, for example, control information indicating whether or not 4K broadcasting is included in the physical channel of the selected 2K broadcasting. Whether or not 4K broadcasting is included in the physical channel can be determined, for example, by bit B of the TMCC information. 110 For example, bit B 110 is 0, it is determined that 4K broadcasting is included, and if it is 1, it is determined that 4K broadcasting is not included. Of the control information decoded by the 4K broadcast control information decoder 27, information indicating that 4K broadcasting is included in the physical channel is output to the controller 50 and stored in the memory 60 within the controller 50.

[0044] The 4K broadcast control information decoder 27 decodes control information related to 4K broadcasting from the signals output from the carrier synchronization unit 24. The control information related to 4K broadcasting is transmitted, for example, by an AC (Auxiliary Channel) signal. The AC signal may include control information indicating whether or not the physical channel of the selected 2K broadcasting includes 4K broadcasting. Of the control information decoded by the 4K broadcast control information decoder 27, information indicating that the physical channel includes 4K broadcasting is output to the control unit 50 and stored in a storage unit 60 within the control unit 50.

[0045] The equalization unit 25 performs equalization processing on the signal output from the carrier synchronization unit 24 to correct amplitude and phase distortion received on the transmission path, and outputs the corrected signal to the deinterleaving unit 28. The equalization unit 25 also outputs C / N information that estimates the quality of the C / N that indicates the quality of the received signal.

[0046] The deinterleave unit 28 performs deinterleaving processing in accordance with the ISDB-T standard on the signal output from the equalization unit 25. The signal processed by the deinterleave unit 28 is output to each of the first error correction processing unit 31 and the second error correction processing unit 32.

[0047] The first error correction processing unit 31 and the second error correction processing unit 32 each operate on a signal based on the same IF signal output from the equalization unit 25 via the deinterleave unit .

[0048] The first error correction processing unit 31 performs Viterbi decoding or RS (Reed-Solomon) decoding on the signals included in the 2K broadcast layer out of the signals output from the deinterleaving unit 28, and outputs a TS (Transport Stream) signal. In this way, the first error correction processing unit 31 performs first error correction processing on the 2K broadcast signal to generate a TS signal corresponding to the 2K broadcast, and outputs this TS signal to the output selection unit 33. The first error correction processing unit 31 also performs error detection on the 2K broadcast signal. The first error correction processing unit 31 outputs error information related to this error detection to the control unit 50.

[0049] The second error correction processing unit 32 performs error correction in accordance with the 4K broadcasting on broadcast signals included in the 4K broadcasting hierarchy among the signals output from the deinterleaving unit 28. For example, if the 4K broadcasting uses Low-Density Parity-Check (LDPC) codes and Bose-Chaudhuri-Hocquenghem (BCH) codes, the second error correction processing unit 32 performs LDPC decoding and BCH decoding on the 4K broadcasting signals to generate TS (or Type Length Value (TLV)) signals corresponding to the 4K broadcasting, and outputs this TS signal to the output selection unit 33. The second error correction processing unit 32 also performs error detection on the 4K broadcasting signals. The second error correction processing unit 32 outputs error information related to this error detection to the control unit 50.

[0050] In this embodiment, a first channel search for 2K broadcasting is performed on multiple physical channels, but a second channel search for 4K broadcasting is performed only on physical channels that were registered as search targets for the second channel search during the first channel search. Therefore, the second error correction processing unit 32 performs second error correction processing only on physical channels that were stored in the storage unit 60 during the first channel search.

[0051] Based on the setting signal output from the control unit 50, the output selection unit 33 selects either a TS signal corresponding to 2K broadcasting or a TS (or TLV) signal corresponding to 4K broadcasting, and outputs the selected signal to the decoding unit 40.

[0052] 2 decodes the signal output from the demodulation unit 20 based on the channel selection instruction signal and setting signal output from the control unit 50. That is, the decoding unit 40 performs decoding processing in accordance with the respective standards on the signal input from the first error correction processing unit 31 or the second error correction processing unit 32 via the output selection unit 33, i.e., the TS signal corresponding to 2K broadcasting or the TS (or TLV) signal corresponding to 4K broadcasting. The decoding unit 40 then outputs to the control unit 50 program information related to the physical channel determined to be error-free by the first error correction processing unit 31 and program information related to the physical channel determined to be error-free by the second error correction processing unit 32. The control unit 50 stores this program information in the storage unit 60.

[0053] The control unit 50 also receives the synchronization information output from the carrier synchronization unit 24, the C / N information output from the equalization unit 25, the control information output from the TMCC decoding unit 26 and the 4K broadcast control information decoding unit 27, the error information output from the first error correction processing unit 31, and the error information output from the second error correction processing unit 32. Based on at least one of these pieces of information, the control unit 50 determines whether a desired digital broadcast signal is present on a physical channel. The control unit 50 then associates the physical channel on which the digital broadcast signal is present with the program information output from the decoding unit 40 and stores them in the storage unit 60. In other words, the storage unit 60 stores the program information output from the decoding unit 40 and the physical channel on which the desired digital broadcast signal is present in an associated state. This completes the channel search of the receiving device 1.

[0054] Next, another configuration of the demodulation unit 20 according to the first embodiment will be described.

[0055] Fig. 4 is a diagram showing another configuration of the demodulation unit 20 according to the first embodiment. Fig. 4 shows the demodulation unit 20 that supports the LDM system. In the LDM system, the broadcast signal of the 4K broadcast is superimposed as power on the broadcast signal of the 2K broadcast, so it is necessary to separate the 2K broadcast from the 4K broadcast.

[0056] As shown in Figure 4, the demodulation unit 20 includes an AD conversion unit 21, a time axis processing unit 22, an FFT unit 23, a carrier synchronization unit 24, an equalization unit 25, a TMCC decoding unit 26, a 4K broadcast control information decoding unit 27, a deinterleaving unit 28, a first error correction processing unit 31, a second error correction processing unit 32, and an output selection unit 33.

[0057] 4 also includes a separation unit 29 for separating the 4K broadcast signal from the broadcast signal of the physical channel. For example, the separation unit 29 creates a replica of the 2K broadcast signal from the signal deinterleaved by the deinterleaving unit 28, subtracts the 2K broadcast signal, performs inverse correction based on the superimposed level, and extracts the 4K broadcast signal. The signal extracted by the separation unit 29 is output to the second error correction processing unit 32.

[0058] The second error correction processing unit 32 performs error correction in accordance with the 4K broadcasting on broadcast signals included in the 4K broadcasting hierarchy among the signals output from the deinterleaving unit 28 via the separating unit 29.

[0059] 4, the second channel search for 4K broadcasts is performed only on physical channels that were registered as search targets for the second channel search during the first channel search. Therefore, the second error correction processing unit 32 performs the second error correction processing only on the physical channels that were stored in the storage unit 60 during the first channel search.

[0060] Based on the setting signal output from the control unit 50, the output selection unit 33 selects either a TS signal corresponding to 2K broadcasting or a TS (or TLV) signal corresponding to 4K broadcasting, and outputs the selected signal to the decoding unit 40.

[0061] The receiving device 1 of this embodiment comprises an AD conversion unit 21, a carrier synchronization unit 24, an equalization unit 25, a deinterleaving unit 28, a first error correction processing unit 31 that performs a first error correction processing on the signal output from the deinterleaving unit 28, and a second error correction processing unit 32 that performs a second error correction processing, and the first error correction processing performed by the first error correction processing unit 31 and the second error correction processing performed by the second error correction processing unit 32 are different.

[0062] In this way, by including the first error correction processing unit 31 and the second error correction processing unit 32, the receiving device 1 can perform error correction processing for the broadcast signals of 2K broadcasts and the broadcast signals of 4K broadcasts, which have different error correction processing methods. For example, while performing a first channel search for 2K broadcasts, it is possible to determine, during the first channel search, physical channels narrowed down to be search targets for a second channel search for 4K broadcasts by referring to the TMCC information. Then, it is possible to perform a second channel search only on the physical channels that are search targets for the second channel search. This reduces the number of physical channels searched in the second channel search, thereby preventing the search time from becoming long.

[0063] [1-2. How to search for channels] A description will be given of a channel search method according to embodiment 1. This channel search method is a method for searching a plurality of physical channels of OFDM digital broadcasting.

[0064] In this embodiment, an example will be described in which a first broadcast of a plurality of digital broadcasts is a 2K broadcast, a second broadcast is a 4K broadcast, and the 2K broadcast and the 4K broadcast are transmitted using a three-layer method or an LDM method.

[0065] These digital broadcasting physical channels are designed to be able to contain both 2K broadcast signals (first broadcast signals) and 4K broadcast signals (second broadcast signals), which use different error correction processing methods. In other words, a single physical channel may contain both 2K and 4K broadcast signals simultaneously, or it may contain only one of them.

[0066] Fig. 5 is a flowchart showing a channel search method according to embodiment 1. Fig. 6 is a diagram showing the search results of the first channel search and the physical channels to be searched in the second channel search.

[0067] As shown in (a) of Figure 5, the channel search method according to the first embodiment includes step S1010 of performing a first channel search and step S1050 of performing a second channel search after step S1010. Specifically, this channel search method includes performing a first channel search for 2K broadcasting on a plurality of physical channels, determining physical channels to be searched in a second channel search for 4K broadcasting during the first channel search, and performing the second channel search on the physical channels that have been searched in the second channel search. Below, the detailed flow of step S1010 will be described in (b) of Figure 5, and the detailed flow of step S1050 will be described in (c) of Figure 5.

[0068] As shown in (b) of Fig. 5, before actually starting a first channel search for 2K broadcasts, the control unit 50 performs 2K broadcast demodulation settings on the demodulation unit 20 and performs 2K broadcast decode settings on the decoding unit 40 (S1011). Note that in the following embodiments, including this embodiment, output settings for the demodulation unit are also performed at the same time as decode settings are performed (the same applies below). After completing these settings, the control unit 50 starts a 2K broadcast channel search.

[0069] First, the control unit 50 determines whether or not the search for all physical channels of 2K broadcasting has been completed (S1012). If the search for all physical channels has not been completed (No in S1012), the control unit 50 starts a channel search for a predetermined physical channel from among the multiple physical channels. The predetermined physical channel may be selected in ascending order of channel number or in ascending order of channel number.

[0070] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S1013). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S1014). Note that the establishment of synchronization means that a digital broadcast signal is present on the physical channel to which the receiving device 1 is tuned.

[0071] If synchronization is not established (No at S1014), the control unit 50 determines that there is no digital broadcast signal on the physical channel to which the receiving device 1 is tuned, and sets the next physical channel for searching for 2K broadcasts (S1030).

[0072] If synchronization is established (Yes in S1014), the control unit 50 acquires demodulation information and control information from the demodulation unit 20 (S1015). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcast with which synchronization is established during the first channel search.

[0073] The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc. Note that the synchronization referred to here refers to frame synchronization synchronized with the timing of the ISDB-T OFDM frame in the demodulation process, but is not limited to this. For example, the synchronization referred to here may be symbol synchronization synchronized with the timing of the symbol, carrier synchronization in which the position of the TMCC is determined, or synchronization based on the ISDB-T signal, such as a state in which the TMCC has been correctly decoded.

[0074] The control information includes information indicating whether or not a 4K broadcast signal is included in the digital broadcast signal being selected (4K broadcast presence / absence information shown in FIG. 6). Note that the control information is included in the TMCC information or AC information of the 2K broadcast signal.

[0075] The control unit 50 determines whether or not the physical channel with which synchronization has been established includes a 4K broadcast based on the control information (S1016). If the physical channel includes a 4K broadcast (Yes in S1016), the control unit 50 determines the physical channel as a search target for the second channel search and registers it in the storage unit 60 (S1017). Note that if the physical channel with which synchronization has been established does not include a 4K broadcast (No in S1016), the physical channel is not considered as a search target for the second channel search, and the process proceeds to the next step, S1018.

[0076] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S1018). The presence or absence of an error is determined, for example, by the presence or absence of an error in the TS packet. Note that, when error correction processing for 2K broadcast is performed using RS code and convolutional code, the control unit 50 may determine the presence or absence of an error based on whether or not correction is possible in RS decoding. Furthermore, the control unit 50 may determine the presence or absence of an error based on the bit error rate after Viterbi decoding (calculated based on the amount of correction made in RS decoding) or the bit error rate after demodulation (calculated based on the amount of correction made in Viterbi decoding). In this case, the presence or absence of an error may be determined based on whether or not the bit error rate is equal to or greater than a predetermined value, rather than based on whether or not correction is possible in RS decoding.

[0077] If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S1018), it does not acquire the 2K broadcast program information and sets the next physical channel (S1030). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S1018), it acquires the 2K broadcast program information from the decoding unit 40 (S1019). After acquiring the 2K broadcast program information, the control unit 50 sets the next physical channel for searching for the 2K broadcast (S1030).

[0078] After step S1030, the control unit 50 determines whether or not the search for all physical channels of 2K broadcasting has been completed (S1012). If the search for all physical channels has not been completed (No in S1012), the control unit 50 executes steps S1012 to S1030 and searches for the next physical channel. On the other hand, if the search for all physical channels of 2K broadcasting has been completed (Yes in S1012), the control unit 50 proceeds to step S1050 and executes a second channel search.

[0079] 5(c), before actually starting the second channel search for 4K broadcasts, the control unit 50 performs 4K broadcast demodulation settings on the demodulation unit 20 and performs 4K broadcast decoding settings on the decoding unit 40 (S1051). After completing these settings, the control unit 50 starts a 4K broadcast channel search.

[0080] The control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S1052). If searching of all physical channels to be searched has not been completed (No in S1052), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0081] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S1053). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S1054).

[0082] If synchronization is not established (No in S1054), the program information of the 4K broadcast cannot be acquired, and the control unit 50 sets the next physical channel from among the search targets (S1070).

[0083] If synchronization is established (Yes in S1054), the control unit 50 acquires demodulation information and control information from the demodulation unit 20 (S1055). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc. The control information is included in the ISDB-T TMCC signal or AC signal.

[0084] Next, the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulation information (S1056). The presence or absence of an error is determined, for example, based on the presence or absence of an error in a TS packet or a TLV packet. Note that, when error correction processing for 4K broadcast is performed using a BCH code and an LDPC code, the control unit 50 may determine the presence or absence of an error based on whether or not correction is possible in BCH decoding. The control unit 50 may also determine the presence or absence of an error based on the bit error rate after LDPC decoding or the bit error rate after demodulation. In this case, the presence or absence of an error may be determined based on whether or not the bit error rate is equal to or greater than a predetermined value, rather than based on whether or not correction is possible in BCH decoding.

[0085] If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S1056), it does not acquire the 4K broadcast program information and sets the next physical channel (S1070). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S1056), it acquires the 4K broadcast program information from the decoding unit 40 (S1059). After acquiring the 4K broadcast program information, the control unit 50 sets the next physical channel from the search targets (S1070).

[0086] After step S1070, the control unit 50 determines whether or not the search of all physical channels to be searched has been completed (S1052).

[0087] If the control unit 50 has not yet completed searching all of the physical channels to be searched (No in S1052), it executes steps S1053 to S1070 again. On the other hand, if the control unit 50 has completed searching all of the physical channels to be searched (Yes in S1052), it ends the second channel search.

[0088] In the channel search method of the first embodiment, the physical channels to be searched in the second channel search are determined based on the control information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting.

[0089] [1-3. Variation 1 of the First Embodiment] A channel search method according to the first modification of the first embodiment will be described.

[0090] In the first modification, an example will be described in which a first broadcast of a plurality of digital broadcasts is a 4K broadcast, a second broadcast is a 2K broadcast, and the 4K broadcast and the 2K broadcast are transmitted in a three-layer format or an LDM format.

[0091] These digital broadcasting physical channels are designed to be able to contain both 4K broadcast signals (first broadcast signals) and 2K broadcast signals (second broadcast signals), which use different error correction processing methods. In other words, a single physical channel may contain both 4K and 2K broadcast signals simultaneously, or it may contain only one of them.

[0092] FIG. 7 is a flowchart showing a channel search method according to the first modification of the first embodiment.

[0093] As shown in (a) of Figure 7, the channel search method according to this first modification includes step S1110 of performing a first channel search and step S1150 of performing a second channel search after step S1110. Specifically, this channel search method includes performing a first channel search for 4K broadcasting on multiple physical channels, determining physical channels to be searched in a second channel search for 2K broadcasting during the first channel search, and performing the second channel search on the physical channels that were searched in the second channel search. Below, the detailed flow of step S1110 will be described in (b) of Figure 7, and the detailed flow of step S1150 will be described in (c) of Figure 7.

[0094] 7(b), before actually starting a first channel search for 4K broadcasts, the control unit 50 performs a demodulation setting for 4K broadcasts on the demodulation unit 20 and a decoding setting for 4K broadcasts on the decoding unit 40 (S1111). After completing these settings, the control unit 50 starts a channel search for 4K broadcasts.

[0095] First, the control unit 50 determines whether or not searching for all physical channels of 4K broadcasting has been completed (S1112). If searching for all physical channels has not been completed (No in S1112), the control unit 50 starts a channel search for a predetermined physical channel from among the multiple physical channels. The predetermined physical channel may be selected from the channel with the smallest channel number or the channel with the largest channel number, and the order does not matter.

[0096] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S1113). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S1114).

[0097] If synchronization is not established (No at S1114), the control unit 50 determines that the specified physical channel does not exist at the current position of the receiving device 1, and sets the next physical channel for searching for 4K broadcasts (S1130).

[0098] If synchronization is established (Yes in S1114), the control unit 50 determines the predetermined physical channel with which synchronization is established as the search target for the second channel search and registers it in the storage unit 60 (S1115).

[0099] In this way, in Modification 1, physical channels with which synchronization is established as 4K broadcasts are targeted for the search of 2K broadcasts, which is the second channel search. On the other hand, in Modification 1, physical channels with which synchronization is not established as 4K broadcasts are removed from the search targets of 2K broadcasts, which is the second channel search, because they do not comply with the ISDB-T standard or the ISDB-T standard signal is weak or non-existent.

[0100] Next, the control unit 50 acquires demodulation information and control information from the demodulation unit 20 (S1116). The demodulation information and control information are acquired from the digital broadcast signal with which synchronization is established during the first channel search.

[0101] The demodulation information includes the synchronization information, C / N information, error information, etc. The control information includes information indicating whether a 4K broadcast signal is included in a specific physical channel. The control information is included in the TMCC information or AC information of the 4K broadcast signal.

[0102] The control unit 50 determines whether or not the physical channel with which synchronization has been established includes a 4K broadcast based on the control information (S1117). If the physical channel does not include a 4K broadcast (No in S1117), the control unit 50 does not register the 4K broadcast and sets the next physical channel (S1130). If the physical channel includes a 4K broadcast (Yes in S1117), the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulation information (S1118).

[0103] If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S1118), it does not acquire the 4K broadcast program information and sets the next physical channel (S1130). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S1118), it acquires the 4K broadcast program information from the decoding unit 40 (S1119). After acquiring the 4K broadcast program information, the control unit 50 sets the next physical channel for searching for the 4K broadcast (S1130).

[0104] After step S1130, the control unit 50 determines whether or not the search for all physical channels of 4K broadcasting has been completed (S1112). If the search for all physical channels has not been completed (No in S1112), the control unit 50 executes steps S1112 to S1130 and searches for the next physical channel. On the other hand, if the search for all physical channels of 4K broadcasting has been completed (Yes in S1112), the control unit 50 proceeds to step S1150 and executes a second channel search.

[0105] 7(c), before actually starting the second channel search for 2K broadcasts, the control unit 50 sets the demodulation unit 20 to demodulation settings for 2K broadcasts and sets the decoding unit 40 to decoding settings for 2K broadcasts (S1151). After completing these settings, the control unit 50 starts a channel search for 2K broadcasts.

[0106] The control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S1152). If searching of all physical channels to be searched has not been completed (No in S1152), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0107] First, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S1153). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S1154).

[0108] If synchronization is not established (No in S1154), the program information of the 2K broadcast cannot be acquired, and the control unit 50 sets the next physical channel from among the search targets (S1170).

[0109] If synchronization is established (Yes in S1154), the control unit 50 acquires demodulation information and control information from the demodulation unit 20 (S1155). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0110] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S1156). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S1156), it does not acquire the 2K broadcast program information and sets the next physical channel (S1170). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S1156), it acquires the 2K broadcast program information from the decoding unit 40 (S1159). After acquiring the 2K broadcast program information, the control unit 50 sets the next physical channel from among the search targets (S1170).

[0111] After step S1170, the control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S1152). If searching of all physical channels to be searched has not been completed (No in S1152), the control unit 50 executes steps S1153 to S1170 again. On the other hand, if searching of all physical channels to be searched has been completed (Yes in S1152), the control unit 50 ends the second channel search.

[0112] In a first modification of the first embodiment, the physical channels to be searched in the second channel search are determined based on the synchronization establishment information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts.

[0113] [1-4. Modification 2 of Embodiment 1] A channel search method according to Modification 2 of Embodiment 1 will be described. Modification 2 describes an example in which it is determined not only whether or not a 4K broadcast is included in a physical channel with which synchronization has been established, but also whether or not there is an error in the layer of the 4K broadcast.

[0114] 8 is a flowchart showing part of a channel search method according to Modification 2 of Embodiment 1. Steps S1211 to S1215 and S1218 to S1230 are the same as steps S1011 to S1015 and S1018 to S1030 in FIG.

[0115] In the second modification, in step S1216 of FIG. 8, the control unit 50 determines whether or not the physical channel with which synchronization has been established includes a 4K broadcast and whether or not there is an error in the layer of the 4K broadcast (S1216).

[0116] If the synchronized physical channel includes 4K broadcasting and there is no error in the 4K broadcasting layer (Yes in S1216), the control unit 50 determines this physical channel as a search target for the second channel search and registers it in the storage unit 60 (S1217). Note that if the synchronized physical channel does not include 4K broadcasting or there is an error in the 4K broadcasting layer (No in S1216), this physical channel is not selected as a search target for the second channel search, and the process proceeds to the next step, S1218. In step S1218, as in the first embodiment, it is determined whether there is an error in the 2K broadcasting layer.

[0117] In the second modification of the first embodiment, the physical channels to be searched in the second channel search are determined based on the control information and error information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming too long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts.

[0118] Furthermore, according to this modification 2, even if 4K broadcasts exist, physical channels that cannot output video signals correctly due to errors in the 4K broadcast hierarchy due to the reception environment or the like can be excluded from the second channel search, which is a search for 4K broadcasts. This prevents the search time from becoming long.

[0119] In the above, the presence or absence of an error in the 4K broadcast layer is checked in step S1216, but this is not limiting. For example, instead of checking the presence or absence of an error in the layer, it may be possible to check whether the reception quality (calculated C / N value) is equal to or greater than a predetermined value and determine whether to include the physical channel in the second channel search.

[0120] [1-5. Modification 3 of Embodiment 1] A description will be given of a channel search method according to Modification 3 of Embodiment 1. In Modification 3, an example will be described in which the presence or absence of 4K broadcasting is not determined in a channel search for 2K broadcasting, but the presence or absence of 4K broadcasting and whether or not there is an error in the 4K broadcasting hierarchy is determined in a channel search for 4K broadcasting.

[0121] 9 is a flowchart showing a channel search method according to Modification 3 of Embodiment 1. Steps S1311 to S1315 and S1318 to S1330 are the same as steps S1011 to S1015 and S1018 to S1030 in FIG. 5(b) of Embodiment 1. Steps S1351 to S1355 and S1356 to S1370 are the same as steps S1051 to S1055 and S1056 to S1070 in FIG. 5(c) of Embodiment 1.

[0122] In Modification 3, the presence or absence of 4K broadcasting is not determined, and in step S1317 of (b) of Fig. 9, the control unit 50 determines the physical channel with which synchronization has been established as the search target of the second channel search and registers it in the storage unit 60 (S1317). Note that if synchronization has not been established (No in S1314), this physical channel is not set as the search target of the second channel search, and the process proceeds to the next step S1330.

[0123] In Modification 3, in step S1356 of FIG. 9(c), the control unit 50 determines whether the physical channel includes 4K broadcasting and whether there is an error in the 4K broadcasting layer (S1356). If the physical channel does not include 4K broadcasting and / or there is an error in the 4K broadcasting layer (No in S1356), the control unit 50 does not acquire 4K broadcasting program information and proceeds to the next step S1370. If the control unit 50 determines that the physical channel includes 4K broadcasting and there is no error in the 4K broadcasting layer (Yes in S1356), the control unit 50 acquires 4K broadcasting program information from the decoding unit 40 (S1359). After acquiring the 4K broadcasting program information, the control unit 50 sets the next physical channel from the search targets (S1370).

[0124] In a third modification of the first embodiment, the physical channels to be searched in the second channel search are determined based on synchronization information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts. Furthermore, according to the third modification, there is no need to check whether 4K broadcasts are available when searching for 2K broadcasts. This prevents the search time from becoming long in the channel search.

[0125] [1-6. Fourth Modification of First Embodiment] A description will be given of a channel search method according to Variation 4 of Embodiment 1. In Variation 4, an example will be described in which the search target of the second channel search for 4K broadcasting is determined based on error information of the broadcast signal of 2K broadcasting.

[0126] 10 is a flowchart showing part of a channel search method according to Variation 4 of Embodiment 1. Steps S1411 to S1415 and S1419 to S1430 are the same as steps S1311 to S1315 and S1319 to S1330 in FIG. 9(b) of Variation 3 of Embodiment 1.

[0127] In Modification 4, in step S1416 of Fig. 10, the control unit 50 determines whether or not there is an error in the 2K broadcast layer (S1416). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S1416), the control unit 50 does not select this physical channel as the search target of the second channel search, and proceeds to the next step S1430. If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S1416), the control unit 50 selects this physical channel as the search target of the second channel search and registers it in the storage unit 60 (S1417).

[0128] Next, the control unit 50 acquires the program information of the 2K broadcast from the decoding unit 40 (S1419). After acquiring the program information of the 2K broadcast, the control unit 50 sets the next physical channel (S1430).

[0129] In a fourth modification of the first embodiment, the physical channels to be searched in the second channel search are determined based on error information acquired during the first channel search. This makes it possible to reduce the number of physical channels to be searched in the second channel search. This makes it possible to prevent the search time from becoming long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts. Furthermore, according to the fourth modification, errors in 2K broadcasts are checked in the channel search for 2K broadcasts, so the search targets of the second channel search can be narrowed down. This makes it possible to prevent the search time of the channel search from becoming long.

[0130] (Embodiment 2) [2-1. Configuration of receiving device] A description will be given of the configuration of a receiving device according to embodiment 2. In embodiment 2, an example will be described in which a 2K broadcast signal is received in accordance with the ISDBT standard, and a 4K broadcast signal is received in accordance with a new broadcast standard conforming to Non-Patent Document 3.

[0131] FIG. 11 is a diagram showing a configuration of a receiving device 1A according to the second embodiment.

[0132] As shown in Fig. 11, the receiving device 1A includes a tuner unit 10, a demodulation unit 20A, a decoding unit 40, a control unit 50, and a display unit 70. The control unit 50 includes a storage unit 60. Fig. 11 also shows an antenna 2 connected to the receiving device 1A.

[0133] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and controls the tuner unit 10. The control unit 50 also outputs a channel selection instruction signal and a setting signal to the demodulation unit 20A and the decoding unit 40, respectively, and controls the demodulation unit 20A and the decoding unit 40.

[0134] An RF signal is input to the tuner unit 10 from the antenna 2. The tuner unit 10 selects a predetermined physical channel based on a tuning instruction signal output from the control unit 50, converts the RF signal corresponding to the predetermined physical channel into an IF signal, and outputs the IF signal to the demodulation unit 20A.

[0135] The demodulation unit 20A performs demodulation processing on the IF signal output from the tuner unit 10. The demodulation unit 20A performs the demodulation processing based on the tuning instruction signal and setting signal output from the control unit 50, and outputs the demodulated signal to the decoding unit 40. The demodulation unit 20A also outputs demodulation information (for example, synchronization information, C / N information, error information) and control information obtained by the demodulation processing to the control unit 50. The demodulation unit 20A of this embodiment performs error correction processing corresponding to each of 2K broadcasting and 4K broadcasting, which will be described later.

[0136] The decoding unit 40 performs a decoding process on the signal output from the demodulation unit 20A. The decoding unit 40 performs the above-mentioned decoding process based on the channel selection instruction signal and setting signal output from the control unit 50, and outputs the decoded video signal to the display unit 70. The decoding unit 40 also outputs the program information obtained by the decoding process to the control unit 50.

[0137] The display unit 70 is a display device such as a display, etc. The display unit 70 displays an image based on the video signal output from the decoding unit 40.

[0138] Fig. 12 is a diagram showing the configuration of a demodulation unit 20A of the receiving device 1A. Fig. 12 shows the demodulation unit 20A that supports the ISDB-T standard and the new broadcasting standard.

[0139] 12, the demodulation unit 20A includes an AD conversion unit 21, a first demodulation unit 20Aa, a second demodulation unit 20Ab, and an output selection unit 33. The first demodulation unit 20Aa performs demodulation processing compatible with ISDB-T, and the second demodulation unit 20Ab performs demodulation processing compatible with a new broadcasting system.

[0140] The first demodulation unit 20Aa includes a time axis processing unit 22a, an FFT unit 23a, a carrier synchronization unit 24a, an equalization unit 25a, a TMCC decoding unit 26a, a deinterleaving unit 28a, and a first error correction processing unit 31a. The second demodulation unit 20Ab includes a time axis processing unit 22b, an FFT unit 23b, a carrier synchronization unit 24b, an equalization unit 25b, a TMCC decoding unit 26b, a deinterleaving unit 28b, and a second error correction processing unit 32b.

[0141] The AD conversion unit 21 performs digital conversion on the IF signal output from the tuner unit 10, and outputs the digitally converted IF signal to the time axis processing unit 22a of the first demodulation unit 20Aa and the time axis processing unit 22b of the second demodulation unit 20Ab.

[0142] The time axis processing unit 22a of the first demodulation unit 20Aa converts the IF signal output from the AD conversion unit 21 into a baseband signal by orthogonal transforming it, and further performs timing synchronization (symbol synchronization) of OFDM symbols of the ISDB-T system. The signal processed by the time axis processing unit 22a is output to the FFT unit 23a.

[0143] The FFT unit 23a performs FFT processing on the signal output from the time axis processing unit 22a to convert it into a signal on the frequency axis, and outputs the converted signal to the carrier synchronization unit 24a.

[0144] The carrier synchronization unit 24a performs a synchronization process of the carrier position on the signal output from the FFT unit 23a, and outputs the signal after the synchronization process to each of the equalization unit 25a and the TMCC decoding unit 26a.

[0145] The TMCC decoder 26a decodes the TMCC signal contained in the ISDB-T frame and synchronizes the ISDB-T OFDM frame using the synchronization word contained in the TMCC signal. The TMCC decoder 26a then outputs synchronization information indicating whether or not synchronization with the selected physical channel has been achieved to the control unit 50, and the equalizer 25 outputs C / N information to the control unit 50.

[0146] The equalizer 25a performs equalization processing on the signal output from the carrier synchronization unit 24a to correct distortion in amplitude and phase received on the transmission path, and outputs the corrected signal to the deinterleaver 28a.

[0147] The deinterleave unit 28a performs deinterleave processing in accordance with the ISDB-T standard on the signal output from the equalizer 25a. The signal processed by the deinterleave unit 28a is output to a first error correction processor 31a.

[0148] The first error correction processing unit 31a operates on a signal based on the IF signal output from the equalization unit 25a via the deinterleave unit 28a.

[0149] The first error correction processing unit 31a performs Viterbi decoding or RS decoding on the signals included in the 2K broadcast layer among the signals output from the deinterleave unit 28a, and outputs a TS signal. In this way, the first error correction processing unit 31a performs the first error correction processing on the 2K broadcast signal to generate a TS signal corresponding to the 2K broadcast, and outputs this TS signal to the output selection unit 33. The first error correction processing unit 31a also performs error detection on the 2K broadcast signal. The first error correction processing unit 31a outputs error information related to this error detection to the control unit 50.

[0150] The time axis processing unit 22b of the second demodulation unit 20Ab converts the IF signal output from the AD conversion unit 21 into a baseband signal by orthogonal transforming it, and further performs timing synchronization (symbol synchronization) of the OFDM symbols of the new broadcasting system. The signal processed by the time axis processing unit 22b is output to the FFT unit 23b.

[0151] The FFT unit 23b performs FFT processing on the signal output from the time axis processing unit 22b to convert it into a frequency axis signal, and outputs the converted signal to the carrier synchronization unit 24b.

[0152] The carrier synchronization unit 24b performs a synchronization process on the carrier position of the signal output from the FFT unit 23b, and outputs the signal after the synchronization process to each of the equalization unit 25b and the TMCC decoding unit 26b.

[0153] The TMCC decoding unit 26b uses the signal output from the carrier synchronization unit 24b to decode the TMCC signal included in the frame of the new broadcasting system, and synchronizes the OFDM frame of the new broadcasting system using the synchronization word included in the TMCC signal. The TMCC decoding unit 26b then outputs synchronization information indicating whether or not synchronization with the selected physical channel has been achieved, and the equalization unit 25b, described later, outputs C / N information to the control unit 50.

[0154] The equalizer 25b performs equalization processing on the signal output from the carrier synchronization unit 24b to correct distortion in amplitude and phase received on the transmission path, and outputs the corrected signal to the deinterleaver 28b.

[0155] The deinterleave unit 28b performs deinterleaving processing conforming to the new broadcasting system on the signal output from the equalizer 25b. The signal processed by the deinterleave unit 28b is output to the second error correction processor 32b.

[0156] The second error correction processing unit 32b performs error correction in accordance with the 4K broadcasting on broadcast signals included in the 4K broadcasting hierarchy among the signals output from the deinterleaving unit 28b. For example, if the 4K broadcasting uses LDPC codes and BCH codes, the second error correction processing unit 32b performs LDPC decoding and BCH decoding on the 4K broadcasting signal to generate a TS (or TLV) signal corresponding to the 4K broadcasting and outputs this TS signal to the output selection unit 33. The second error correction processing unit 32b also performs error detection on the 4K broadcasting signal. The second error correction processing unit 32b outputs error information related to this error detection to the control unit 50.

[0157] In this embodiment, a first channel search for 2K broadcasting is performed on multiple physical channels, but a second channel search for 4K broadcasting is performed only on physical channels that were registered as search targets for the second channel search during the first channel search. Therefore, with regard to error correction processing, the second error correction processing unit 32b performs second error correction processing only on physical channels that were stored in the storage unit 60 during the first channel search. This makes it possible to reduce the number of physical channels searched in the second channel search, thereby preventing the search time from becoming too long.

[0158] Based on the setting signal output from the control unit 50, the output selection unit 33 selects either a TS signal corresponding to 2K broadcasting or a TS (or TLV) signal corresponding to 4K broadcasting, and outputs the selected signal to the decoding unit 40.

[0159] 11 decodes the signal output from the demodulation unit 20A based on the tuning instruction signal and setting signal output from the control unit 50. That is, the decoding unit 40 performs decoding processing in accordance with the respective standards on the signal input from the first error correction processing unit 31a or the second error correction processing unit 32b via the output selection unit 33, i.e., the TS signal corresponding to 2K broadcasting or the TS (or TLV) signal corresponding to 4K broadcasting. The decoding unit 40 then outputs to the control unit 50 program information related to the physical channel determined to be error-free by the first error correction processing unit 31a and program information related to the physical channel determined to be error-free by the second error correction processing unit 32b. The control unit 50 stores this program information in the storage unit 60.

[0160] The control unit 50 also receives the synchronization information output from the carrier synchronization units 24a and 24b, the C / N information output from the equalization units 25a and 25b, the control information output from the TMCC decoding units 26a and 26b, the error information output from the first error correction processing unit 31, and the error information output from the second error correction processing unit 32. Based on at least one of these pieces of information, the control unit 50 determines whether a desired digital broadcast signal is present on a physical channel. The control unit 50 then associates the physical channel on which the digital broadcast signal is present with the program information output from the decoding unit 40 and stores them in the storage unit 60. In other words, the storage unit 60 stores the program information output from the decoding unit 40 and the physical channel on which the desired digital broadcast signal is present in an associated state. This completes the channel search of the receiving device 1A.

[0161] The receiving device 1A of this embodiment comprises an AD conversion unit 21, carrier synchronization units 24a, 24b, equalization units 25a, 25b, deinterleaving units 28a, 28b, a first error correction processing unit 31a that performs a first error correction process on the signal output from the deinterleaving unit 28a, and a second error correction processing unit 32b that performs a second error correction process on the signal output from the deinterleaving unit 28b, and the first error correction process performed by the first error correction processing unit 31a is different from the second error correction process performed by the second error correction processing unit 32b.

[0162] In this way, by having the receiving device 1A with the first error correction processing unit 31a and the second error correction processing unit 32b, it is possible to perform error correction processing on the broadcast signals of 2K broadcasting and 4K broadcasting, which have different error correction processing methods.

[0163] [2-2. How to search for channels] A description will now be given of a channel search method according to embodiment 2. This channel search method is a method for searching a plurality of physical channels of OFDM digital broadcasting.

[0164] In this embodiment, an example will be described in which a first broadcast among multiple digital broadcasts is a 2K broadcast, a second broadcast is a 4K broadcast, the 2K broadcast is transmitted in the ISDB-T format, and the 4K broadcast is transmitted in a new broadcast format.

[0165] These digital broadcasting physical channels are designed to be capable of containing either a 2K broadcast signal (first broadcast signal) or a 4K broadcast signal (second broadcast signal), which have different error correction processing methods. In other words, each of the multiple physical channels contains either a 2K broadcast signal or a 4K broadcast signal.

[0166] Fig. 13 is a flowchart showing a channel search method according to embodiment 2. Fig. 14 is a diagram showing the search results of the first channel search and the physical channels to be searched in the second channel search.

[0167] As shown in (a) of Figure 13, the channel search method according to the second embodiment includes step S2010 of performing a first channel search and step S2050 of performing a second channel search after step S2010. Specifically, this channel search method includes performing a first channel search for 2K broadcasting on a plurality of physical channels, determining physical channels to be searched in a second channel search for 4K broadcasting during the first channel search, and performing the second channel search on the physical channels that have been searched in the second channel search. Below, the detailed flow of step S2010 will be described in (b) of Figure 13, and the detailed flow of step S2050 will be described in (c) of Figure 13.

[0168] 13(b), before actually starting a first channel search for 2K broadcasts, the control unit 50 performs demodulation settings for 2K broadcasts based on the ISDB-T standard on the first demodulation unit 20Aa, and performs decoding settings for 2K broadcasts based on the ISDB-T standard on the decoding unit 40 (S2011). After completing these settings, the control unit 50 starts a channel search for 2K broadcasts.

[0169] First, the control unit 50 determines whether or not the search for all physical channels of 2K broadcasting has been completed (S2012). If the search for all physical channels has not been completed (No in S2012), the control unit 50 starts a channel search for a predetermined physical channel from among the multiple physical channels. The predetermined physical channel may be selected in ascending order of channel number or in ascending order of channel number.

[0170] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S2013). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S2014).

[0171] If synchronization is not established (No in S2014), the control unit 50 determines the physical channel with which synchronization is not established as the search target for the second channel search and registers it in the storage unit 60 (S2017), as shown in Fig. 14. Then, the control unit 50 sets the next physical channel for searching for 2K broadcasts (S2030).

[0172] In the second embodiment, since one physical channel contains either a 2K broadcast signal or a 4K broadcast signal, there is a possibility that a physical channel that has not been synchronized with the 2K broadcast may contain a 4K broadcast signal. Therefore, the physical channel that has not been synchronized with the 2K broadcast is set as the search target for the 4K broadcast, which is the second channel search.

[0173] On the other hand, since the physical channel for which synchronization has been established as 2K broadcasting does not contain a broadcast signal for 4K broadcasting, when synchronization is established (Yes in S2014), this physical channel is not targeted for the search for 4K broadcasting, which is the second channel search, and the control unit 50 executes the following steps for this physical channel.

[0174] The control unit 50 acquires demodulation information and control information from the first demodulation unit 20Aa (S2015). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcast with which synchronization is established during the first channel search.

[0175] The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc. Note that the synchronization referred to here refers to frame synchronization synchronized with the timing of the ISDB-T OFDM frame in the demodulation process, but is not limited to this. For example, the synchronization referred to here may be symbol synchronization synchronized with the timing of the symbol, carrier synchronization in which the position of the TMCC is determined, or synchronization based on the ISDB-T signal, such as a state in which the TMCC has been correctly decoded.

[0176] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S2018). The presence or absence of an error is determined, for example, by the presence or absence of an error in the TS packet. Note that, when error correction processing for 2K broadcast is performed using RS code and convolutional code, the control unit 50 may determine the presence or absence of an error based on whether or not correction is possible in RS decoding. The control unit 50 may also determine the presence or absence of an error based on the bit error rate after Viterbi decoding or the bit error rate after demodulation. In this case, the presence or absence of an error may be determined based on whether or not the bit error rate is equal to or greater than a predetermined value, rather than determining the presence or absence of an error based on whether or not correction is possible in RS decoding.

[0177] If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S2018), it does not acquire the 2K broadcast program information and sets the next physical channel (S2030). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S2018), it acquires the 2K broadcast program information from the decoding unit 40 (S2019). After acquiring the 2K broadcast program information, the control unit 50 sets the next physical channel for searching for the 2K broadcast (S2030).

[0178] After step S2030, the control unit 50 determines whether or not the search for all physical channels of 2K broadcasting has been completed (S2012). If the search for all physical channels has not been completed (No in S2012), the control unit 50 executes steps S2012 to S2030 and searches for the next physical channel. On the other hand, if the search for all physical channels of 2K broadcasting has been completed (Yes in S2012), the control unit 50 proceeds to step S2050 and executes a second channel search.

[0179] 13(c), before actually starting the second channel search for 4K broadcasts, the control unit 50 performs demodulation settings for 4K broadcasts based on the new broadcasting standard on the second demodulation unit 20Ab, and also performs decoding settings for 4K broadcasts based on the new broadcasting standard on the decoding unit 40 (S2051). After completing these settings, the control unit 50 starts a channel search for 4K broadcasts.

[0180] The control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S2052). If searching of all physical channels to be searched has not been completed (No in S2052), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0181] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S2053). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S2054).

[0182] If synchronization is not established (No in S2054), the program information of the 4K broadcast cannot be acquired, and therefore the control unit 50 sets the next physical channel from among the search targets (S2070).

[0183] If synchronization is established (Yes in S2054), the control unit 50 acquires demodulation information and control information from the second demodulation unit 20Ab (S2055). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0184] The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc. Note that the synchronization referred to here refers to frame synchronization synchronized with the timing of the OFDM frame of the new broadcasting system in the demodulation process, but is not limited to this. For example, the synchronization referred to here may be symbol synchronization synchronized with the timing of the symbol, carrier synchronization in which the position of the TMCC is determined, or synchronization based on the signal of the new broadcasting system, such as a state in which TMCC decoding has been correctly performed.

[0185] Next, the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulation information (S2056). The presence or absence of an error is determined, for example, based on the presence or absence of an error in a TS packet or a TLV packet. Note that, when error correction processing for 4K broadcast is performed using a BCH code and an LDPC code, the control unit 50 may determine the presence or absence of an error based on whether or not correction is possible in BCH decoding. The control unit 50 may also determine the presence or absence of an error based on the bit error rate after LDPC decoding or the bit error rate after demodulation. In this case, the presence or absence of an error may be determined based on whether or not the bit error rate is equal to or greater than a predetermined value, rather than based on whether or not correction is possible in BCH decoding.

[0186] If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S2056), it does not acquire the 4K broadcast program information and sets the next physical channel (S2070). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S2056), it acquires the 4K broadcast program information from the decoding unit 40 (S2059). After acquiring the 4K broadcast program information, the control unit 50 sets the next physical channel from the search targets (S2070).

[0187] After step S2070, the control unit 50 determines whether or not the search of all physical channels to be searched has been completed (S2052).

[0188] If the control unit 50 has not yet completed searching all of the physical channels to be searched (No in S2052), it executes steps S2053 to S2070 again. On the other hand, if the control unit 50 has completed searching all of the physical channels to be searched (Yes in S2052), it ends the second channel search.

[0189] In the channel search method of the second embodiment, the physical channels to be searched in the second channel search are determined based on the synchronization information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting.

[0190] [2-3. Variation 1 of Embodiment 2] A channel search method according to the first modification of the second embodiment will be described.

[0191] In this variant example 1, an example is described in which the first of multiple digital broadcasts is a 4K broadcast, the second is a 2K broadcast, the 4K broadcast is transmitted using a new broadcasting standard, and the 2K broadcast is transmitted using the ISDB-T standard.

[0192] These digital broadcasting physical channels are designed to be capable of containing either a 4K broadcast signal (first broadcast signal) or a 2K broadcast signal (second broadcast signal), which have different error correction processing methods. In other words, each of the multiple physical channels contains either a 4K broadcast signal or a 2K broadcast signal.

[0193] FIG. 15 is a flowchart showing a channel search method according to the first modification of the second embodiment.

[0194] As shown in (a) of Figure 15, the channel search method according to this first modification includes step S2110 of performing a first channel search and step S2150 of performing a second channel search after step S2110. Specifically, this channel search method includes performing a first channel search for 4K broadcasting on multiple physical channels, determining physical channels to be searched in a second channel search for 2K broadcasting during the first channel search, and performing the second channel search on the physical channels that were searched in the second channel search. Below, the detailed flow of step S2110 is described in (b) of Figure 15, and the detailed flow of step S2150 is described in (c) of Figure 15.

[0195] 15(b), before actually starting the first channel search for 4K broadcasts, the control unit 50 performs demodulation settings for 4K broadcasts based on the new broadcasting standard on the second demodulation unit 20Ab, and also performs decoding settings for 4K broadcasts based on the new broadcasting standard on the decoding unit 40 (S2111). After completing these settings, the control unit 50 starts a channel search for 4K broadcasts.

[0196] First, the control unit 50 determines whether or not the search for all physical channels of 4K broadcasting has been completed (S2112). If the search for all physical channels has not been completed (No in S2112), the control unit 50 starts a channel search for a predetermined physical channel from among the multiple physical channels. The predetermined physical channel may be selected in ascending order of channel number or in ascending order of channel number.

[0197] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S2113). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S2114).

[0198] If synchronization is not established (No in S2114), the control unit 50 determines the physical channel with which synchronization is not established as the search target for the second channel search and registers it in the storage unit 60 (S2117).Then, the control unit 50 sets the next physical channel for searching for 4K broadcasts (S2130).

[0199] Even in this variation 1, since one physical channel contains either a 4K broadcast signal or a 2K broadcast signal, there is a possibility that a physical channel that has not been synchronized with the 4K broadcast may contain a 2K broadcast signal. Therefore, the physical channel that has not been synchronized with the 4K broadcast is set as the target of the second channel search for the 2K broadcast.

[0200] On the other hand, since the physical channel for which synchronization has been established as 4K broadcasting does not contain a broadcast signal for 2K broadcasting, when synchronization is established (Yes in S2114), this physical channel is not targeted for the search for 2K broadcasting, which is the second channel search, and the control unit 50 executes the following steps for this physical channel.

[0201] The control unit 50 acquires demodulation information and control information from the second demodulation unit 20Ab (S2115). The demodulation information and control information are acquired from the 4K broadcast signal with which synchronization was established during the first channel search. The demodulation information includes the synchronization information, C / N information, error information, etc.

[0202] Next, the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulation information (S2118). If the control unit 50 determines that there is an error in the layer of the 4K broadcast (Yes in S2118), it does not acquire the program information of the 4K broadcast and sets the next physical channel (S2130). If the control unit 50 determines that there is no error in the layer of the 4K broadcast (No in S2118), it acquires the program information of the 4K broadcast from the decoding unit 40 (S2119). After acquiring the program information of the 4K broadcast, the control unit 50 sets the next physical channel for searching for the 4K broadcast (S2130).

[0203] After step S2130, the control unit 50 determines whether or not searching for all physical channels of 4K broadcasting is complete (S2112). If searching for all physical channels has not been completed (No in S2112), the control unit 50 executes steps S2112 to S2130 and searches for the next physical channel. On the other hand, if searching for all physical channels of 4K broadcasting is completed (Yes in S2112), the control unit 50 proceeds to step S2150 and executes a second channel search.

[0204] 15(c), before actually starting the second channel search for 2K broadcasts, the control unit 50 sets the first demodulation unit 20Aa to demodulation settings for 2K broadcasts based on the ISDB-T standard, and sets the decoding unit 40 to decoding settings for 2K broadcasts based on the ISDB-T standard (S2151). After completing these settings, the control unit 50 starts a channel search for 2K broadcasts.

[0205] The control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S2152). If searching of all physical channels to be searched has not been completed (No in S2152), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0206] First, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S2153). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S2154).

[0207] If synchronization is not established (No in S2154), the program information of the 2K broadcast cannot be acquired, and therefore the control unit 50 sets the next physical channel from among the search targets (S2170).

[0208] If synchronization is established (Yes in S2154), the control unit 50 acquires demodulation information and control information from the first demodulation unit 20Aa (S2155). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0209] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S2156). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S2156), it does not acquire the 2K broadcast program information and sets the next physical channel (S2170). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S2156), it acquires the 2K broadcast program information from the decoding unit 40 (S2159). After acquiring the 2K broadcast program information, the control unit 50 sets the next physical channel from the search targets (S2170).

[0210] After step S2170, the control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S2152). If searching of all physical channels to be searched has not been completed (No in S2152), the control unit 50 executes steps S2153 to S2170 again. On the other hand, if searching of all physical channels to be searched has been completed (Yes in S2152), the control unit 50 ends the second channel search.

[0211] In a first modification of the second embodiment, the physical channels to be searched in the second channel search are determined based on synchronization information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches for both 4K broadcasts and 2K broadcasts.

[0212] (Embodiment 3) [3-1. Configuration of receiving device] The configuration of a receiving device according to embodiment 3 will be described. In embodiment 3, an example will be described in which, as in embodiment 2, 2K broadcast signals are received in the ISDB-T system and 4K broadcast signals are received in a new broadcast system. Also, in embodiment 3, an example will be described in which the physical channels to be searched in the second channel search are determined using the in-band power values ​​of the physical channels.

[0213] FIG. 16 is a diagram showing a configuration of a receiving device 1B according to the third embodiment.

[0214] As shown in Fig. 16, the receiving device 1B includes a tuner unit 10B, a demodulation unit 20B, a decoding unit 40, a control unit 50, and a display unit 70. The control unit 50 includes a storage unit 60. Fig. 16 also shows an antenna 2 connected to the receiving device 1B. The demodulation unit 20B of the third embodiment has the same configuration as the demodulation unit 20A of the second embodiment.

[0215] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10B and controls the tuner unit 10B. The control unit 50 also outputs a channel selection instruction signal and a setting signal to the demodulation unit 20B and the decoding unit 40, respectively, and controls the demodulation unit 20B and the decoding unit 40.

[0216] The tuner unit 10B receives an RF signal input from the antenna 2. The tuner unit 10B selects a predetermined physical channel based on a tuning instruction signal output from the control unit 50, converts the RF signal corresponding to the predetermined physical channel into an IF signal, and outputs the IF signal to the demodulation unit 20B.

[0217] Furthermore, the tuner unit 10B of this embodiment outputs to the control unit 50 power information relating to the in-band power value of the selected physical channel.

[0218] The demodulation unit 20B performs demodulation processing on the IF signal output from the tuner unit 10B. The demodulation unit 20B performs the demodulation processing based on the tuning instruction signal and setting signal output from the control unit 50, and outputs the demodulated signal to the decoding unit 40. The demodulation unit 20B also outputs demodulation information (for example, synchronization information, C / N information, error information) and control information obtained by the demodulation processing to the control unit 50. The demodulation unit 20B of this embodiment performs error correction processing corresponding to each of 2K broadcasting and 4K broadcasting.

[0219] The decoding unit 40 performs a decoding process on the signal output from the demodulation unit 20B. The decoding unit 40 performs the above-mentioned decoding process based on the channel selection instruction signal and setting signal output from the control unit 50, and outputs the decoded video signal to the display unit 70. The decoding unit 40 also outputs the program information obtained by the decoding process to the control unit 50.

[0220] The display unit 70 is a display device such as a display, etc. The display unit 70 displays an image based on the video signal output from the decoding unit 40.

[0221] Fig. 17 is a diagram showing the configuration of a demodulation unit 20B of the receiving device 1B. Fig. 17 shows a demodulation unit 20B that supports the ISDB-T standard and the new broadcasting standard.

[0222] 17, the demodulation unit 20B includes an AD conversion unit 21, a first demodulation unit 20Ba, a second demodulation unit 20Bb, and an output selection unit 33. The first demodulation unit 20Ba performs demodulation processing compatible with ISDB-T, and the second demodulation unit 20Bb performs demodulation processing compatible with a new broadcasting system. The first demodulation unit 20Ba has a configuration similar to that of the first demodulation unit 20Aa, and the second demodulation unit 20Bb has a configuration similar to that of the second demodulation unit 20Ab.

[0223] The first demodulation unit 20Ba includes a time axis processing unit 22a, an FFT unit 23a, a carrier synchronization unit 24a, an equalization unit 25a, a TMCC decoding unit 26a, a deinterleaving unit 28a, and a first error correction processing unit 31a. The second demodulation unit 20Bb includes a time axis processing unit 22b, an FFT unit 23b, a carrier synchronization unit 24b, an equalization unit 25b, a TMCC decoding unit 26b, a deinterleaving unit 28b, and a second error correction processing unit 32b.

[0224] In this embodiment, a first channel search for 2K broadcasting is performed on multiple physical channels, but a second channel search for 4K broadcasting is performed only on physical channels that were registered as search targets for the second channel search during the first channel search. Therefore, with regard to error correction processing, the second error correction processing unit 32b performs second error correction processing only on physical channels that were stored in the storage unit 60 during the first channel search. This makes it possible to reduce the number of physical channels searched in the second channel search, thereby preventing the search time from becoming too long.

[0225] Based on the setting signal output from the control unit 50, the output selection unit 33 selects either a TS signal corresponding to 2K broadcasting or a TS (or TLV) signal corresponding to 4K broadcasting, and outputs the selected signal to the decoding unit 40.

[0226] 16 decodes the signal output from the demodulation unit 20B based on the tuning instruction signal and setting signal output from the control unit 50. That is, the decoding unit 40 performs decoding processing in accordance with the respective standards on the signal input from the first error correction processing unit 31a or the second error correction processing unit 32b via the output selection unit 33, i.e., the TS signal corresponding to 2K broadcasting or the TS (or TLV) signal corresponding to 4K broadcasting. The decoding unit 40 then outputs to the control unit 50 program information related to the physical channel determined to be error-free by the first error correction processing unit 31a and program information related to the physical channel determined to be error-free by the second error correction processing unit 32b. The control unit 50 stores this program information in the storage unit 60.

[0227] Furthermore, the control unit 50 determines whether or not a desired digital broadcast signal is present on the physical channel based on the demodulation information (synchronization information, C / N information, error information) output from the demodulation unit 20B and information related to the in-band power value of the selected physical channel. Then, the control unit 50 associates the physical channel on which the desired digital broadcast signal is present with the program information output from the decoding unit 40 and stores them in the storage unit 60. In other words, the storage unit 60 stores the program information output from the decoding unit 40 and the physical channel on which the desired digital broadcast signal is present in an associated state. This completes the channel search of the receiving device 1B.

[0228] The receiving device 1B of this embodiment includes an AD conversion unit 21, carrier synchronization units 24a, 24b, equalization units 25a, 25b, deinterleaving units 28a, 28b, a first error correction processing unit 31a that performs a first error correction process on the signal output from the deinterleaving unit 28a, and a second error correction processing unit 32b that performs a second error correction process on the signal output from the deinterleaving unit 28b, and the first error correction process performed by the first error correction processing unit 31a is different from the second error correction process performed by the second error correction processing unit 32b.

[0229] In this way, by having the receiving device 1B with the first error correction processing unit 31a and the second error correction processing unit 32b, it is possible to perform error correction processing on the broadcast signals of 2K broadcasting and 4K broadcasting, which have different error correction processing methods.

[0230] [3-2. How to search for channels] A description will be given of a channel search method according to embodiment 3. This channel search method is a method for searching a plurality of physical channels of OFDM digital broadcasting.

[0231] In this embodiment, an example will be described in which a first broadcast among multiple digital broadcasts is a 2K broadcast, a second broadcast is a 4K broadcast, the 2K broadcast is transmitted in the ISDB-T format, and the 4K broadcast is transmitted in a new broadcast format.

[0232] These digital broadcasting physical channels are designed to be capable of containing either a 2K broadcast signal (first broadcast signal) or a 4K broadcast signal (second broadcast signal), which have different error correction processing methods. In other words, each of the multiple physical channels contains either a 2K broadcast signal or a 4K broadcast signal.

[0233] FIG. 18 is a flowchart showing a channel search method according to the third embodiment.

[0234] As shown in (a) of Figure 18, the channel search method according to embodiment 3 includes step S3010 of performing a first channel search and step S3050 of performing a second channel search after step S3010. Specifically, this channel search method includes performing a first channel search for 2K broadcasting on multiple physical channels, determining physical channels to be searched in a second channel search for 4K broadcasting during the first channel search, and performing the second channel search on the physical channels that have been searched in the second channel search. Below, the detailed flow of step S3010 will be described in (b) of Figure 18, and the detailed flow of step S3050 will be described in (c) of Figure 18.

[0235] 18(b), before actually starting a first channel search for 2K broadcasts, the control unit 50 performs demodulation settings for 2K broadcasts based on the ISDB-T standard on the first demodulation unit 20Ba, and performs decoding settings for 2K broadcasts based on the ISDB-T standard on the decoding unit 40 (S3011). After completing these settings, the control unit 50 starts a channel search for 2K broadcasts.

[0236] First, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting has been completed (S3012). If searching for all physical channels has not been completed (No in S3012), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0237] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10B to select a predetermined physical channel (S3013). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10B (S3014).

[0238] If synchronization has not been established (No in S3014), the control unit 50 determines whether the in-band power value of the predetermined physical channel is equal to or greater than a predetermined threshold value (S3016).

[0239] If the in-band power value of the predetermined physical channel is not equal to or greater than the predetermined threshold (No in S3016), the control unit 50 sets the next physical channel for searching for 2K broadcasts (S3030). On the other hand, if the in-band power value of the predetermined physical channel is equal to or greater than the predetermined threshold (Yes in S3016), the control unit 50 determines this physical channel as a search target for the second channel search and registers it in the storage unit 60 (S3017). Specifically, the control unit 50 registers in the storage unit 60 a physical channel for which synchronization has not been established and whose in-band power value is equal to or greater than the predetermined threshold. Then, the control unit 50 sets the next physical channel (S3030).

[0240] If synchronization is established (Yes in S3014), the control unit 50 acquires demodulation information and control information from the first demodulation unit 20Ba (S3015).

[0241] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S3018). If the control unit 50 determines that there is an error in the layer of the 2K broadcast (Yes in S3018), it does not acquire the program information of the 2K broadcast and sets the next physical channel (S3030). If the control unit 50 determines that there is no error in the layer of the 2K broadcast (No in S3018), it acquires the program information of the 2K broadcast from the decoding unit 40 (S3019). After acquiring the program information of the 2K broadcast, the control unit 50 sets the next physical channel for searching for the 2K broadcast (S3030).

[0242] After step S3030, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting is complete (S3012). If searching for all physical channels has not been completed (No in S3012), the control unit 50 executes steps S3012 to S3030 and searches for the next physical channel. If searching for all physical channels of 2K broadcasting is completed (Yes in S3012), the control unit 50 proceeds to step S3050 and executes a second channel search.

[0243] 18(c), before actually starting the second channel search for 4K broadcasts, the control unit 50 performs demodulation settings for 4K broadcasts based on the new broadcasting standard on the second demodulation unit 20Bb, and also performs decoding settings for 4K broadcasts based on the new broadcasting standard on the decoding unit 40 (S3051). After completing these settings, the control unit 50 starts a channel search for 4K broadcasts.

[0244] The control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S3052). If searching of all physical channels to be searched has not been completed (No in S3052), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0245] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10B to select a predetermined physical channel (S3053). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10B (S3054).

[0246] If synchronization is not established (No in S3054), the control unit 50 cannot acquire the program information of the 4K broadcast, and therefore sets the next physical channel from among the search targets (S3070).

[0247] If synchronization is established (Yes in S3054), the control unit 50 acquires demodulation information and control information from the second demodulation unit 20Bb (S3055).

[0248] Next, the control unit 50 determines whether or not there is an error in the 4K broadcast layer based on the demodulation information (S3056). If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S3056), it does not acquire the 4K broadcast program information and sets the next physical channel (S3070). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S3056), it acquires the 4K broadcast program information from the decoding unit 40 (S3059). After acquiring the 4K broadcast program information, the control unit 50 sets the next physical channel from the search targets (S3070).

[0249] After step S3070, the control unit 50 determines whether or not the search of all physical channels to be searched has been completed (S3052).

[0250] If the control unit 50 has not yet completed searching all of the physical channels to be searched (No in S3052), it executes steps S3053 to S3070 again. On the other hand, if the control unit 50 has completed searching all of the physical channels to be searched (Yes in S3052), it ends the second channel search.

[0251] In the channel search method of the third embodiment, the physical channels to be searched in the second channel search are determined based on the synchronization information and the information on the in-band power value acquired during the first channel search. This makes it possible to reduce the number of physical channels to be searched in the second channel search. This makes it possible to prevent the search time from becoming long when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting.

[0252] [3-3. Variation 1 of Embodiment 3] A description will be given of a channel search method according to Modification 1 of Embodiment 3. In Modification 1, an example will be described in which it is determined whether or not the in-band power value of a physical channel is equal to or greater than a predetermined threshold before determining whether synchronization has been established for 2K broadcasting.

[0253] 19 is a flowchart showing part of a channel search method according to Modification 1 of Embodiment 3. Steps S3111 to S3113 and S3118 to S3130 are the same as steps S3011 to S3013 and S3018 to S3030 in FIG.

[0254] In this first modification, in step S3114 of FIG. 19, the control unit 50 determines whether the in-band power value of a predetermined physical channel is equal to or greater than a predetermined threshold (S3114).

[0255] If the in-band power value of the predetermined physical channel is low and not equal to or greater than the predetermined threshold (No in S3114), the control unit 50 sets the next physical channel for searching for 2K broadcasts (S3130). On the other hand, if the in-band power value of the predetermined physical channel is equal to or greater than the predetermined threshold (Yes in S3114), the control unit 50 outputs a tuning instruction signal to the tuner unit 10B and determines whether synchronization has been established with the frequency of the predetermined physical channel (S3115).

[0256] If synchronization has not been established (No in S3115), the control unit 50 determines this physical channel as a search target for the second channel search and registers it in the storage unit 60 (S3116). Specifically, the control unit 50 registers in the storage unit 60 a physical channel whose in-band power value is equal to or greater than a predetermined threshold and for which synchronization has not been established. Then, the control unit 50 sets the next physical channel (S3130).

[0257] If synchronization is established (Yes in S3114), the control unit 50 acquires demodulation information and control information from the first demodulation unit 20Ba (S3117).

[0258] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S3118). If the control unit 50 determines that there is an error in the layer of the 2K broadcast (Yes in S3118), it does not acquire the program information of the 2K broadcast and sets the next physical channel (S3130). If the control unit 50 determines that there is no error in the layer of the 2K broadcast (No in S3118), it acquires the program information of the 2K broadcast from the decoding unit 40 (S3119). After acquiring the program information of the 2K broadcast, the control unit 50 sets the next physical channel for searching for the 2K broadcast (S3130).

[0259] After step S3130, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting is complete (S3112). If searching for all physical channels has not been completed (No in S3112), the control unit 50 executes steps S3112 to S3130 and searches for the next physical channel. On the other hand, if searching for all physical channels of 2K broadcasting is completed (Yes in S3112), the control unit 50 executes a second channel search.

[0260] In a first modification of the third embodiment, the physical channels to be searched in the second channel search are determined based on synchronization information and information related to in-band power values ​​acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from increasing when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting. Furthermore, according to the first modification of the third embodiment, physical channels with large in-band power values ​​can be omitted from the second channel search, which is a search for 4K broadcasting, at an early stage.

[0261] [3-4. Modification 2 of Embodiment 3] A channel search method according to the second modification of the third embodiment will be described.

[0262] In this variant example 2, an example is described in which the first of multiple digital broadcasts is a 4K broadcast, the second is a 2K broadcast, the 4K broadcast is transmitted using a new broadcasting standard, and the 2K broadcast is transmitted using the ISDB-T standard.

[0263] These digital broadcasting physical channels are designed to be capable of containing either a 4K broadcast signal (first broadcast signal) or a 2K broadcast signal (second broadcast signal), which have different error correction processing methods. In other words, each of the multiple physical channels contains either a 4K broadcast signal or a 2K broadcast signal.

[0264] FIG. 20 is a flowchart showing a channel search method according to the second modification of the third embodiment.

[0265] As shown in (a) of Figure 20, the channel search method according to this second modification includes step S3210 of performing a first channel search and step S3250 of performing a second channel search after step S3210. Specifically, this channel search method includes performing a first channel search for 4K broadcasting on multiple physical channels, determining physical channels to be searched in a second channel search for 2K broadcasting during the first channel search, and performing the second channel search on the physical channels that were searched in the second channel search. Below, the detailed flow of step S3210 is described in (b) of Figure 20, and the detailed flow of step S3250 is described in (c) of Figure 20.

[0266] 20(b), before actually starting the first channel search for 4K broadcasts, the control unit 50 performs demodulation settings for 4K broadcasts based on the new broadcasting standard on the second demodulation unit 20Bb, and also performs decoding settings for 4K broadcasts based on the new broadcasting standard on the decoding unit 40 (S3211). After completing these settings, the control unit 50 starts a channel search for 4K broadcasts.

[0267] First, the control unit 50 determines whether or not searching for all physical channels of 4K broadcasting has been completed (S3212). If searching for all physical channels has not been completed (No in S3212), the control unit 50 starts a channel search for a specific physical channel from among the multiple physical channels.

[0268] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10B to select a predetermined physical channel (S3213). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10B (S3214).

[0269] If synchronization has not been established (No in S3214), the control unit 50 determines whether the in-band power value of the predetermined physical channel is equal to or greater than a predetermined threshold value (S3216).

[0270] If the in-band power value of the predetermined physical channel is not equal to or greater than the predetermined threshold (No in S3216), the control unit 50 sets the next physical channel for searching for 4K broadcasts (S3230). On the other hand, if the in-band power value of the predetermined physical channel is equal to or greater than the predetermined threshold (Yes in S3216), the control unit 50 determines this physical channel as a search target for the second channel search and registers it in the storage unit 60 (S3217). Specifically, the control unit 50 registers in the storage unit 60 a physical channel for which synchronization has not been established and whose in-band power value is equal to or greater than the predetermined threshold. Then, the control unit 50 sets the next physical channel (S3230).

[0271] If synchronization is established (Yes in S3214), the control unit 50 acquires demodulation information and control information from the second demodulation unit 20Bb (S3215).

[0272] Next, the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulated information (S3218).

[0273] If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S3218), it does not acquire the 4K broadcast program information and sets the next physical channel (S3230). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S3218), it acquires the 4K broadcast program information from the decoding unit 40 (S3219). After acquiring the 4K broadcast program information, the control unit 50 sets the next physical channel for searching for the 4K broadcast (S3230).

[0274] After step S3230, the control unit 50 determines whether or not the search for all physical channels of 4K broadcasting has been completed (S3212). If the search for all physical channels has not been completed (No in S3212), the control unit 50 executes steps S3212 to S3230 and searches for the next physical channel. On the other hand, if the search for all physical channels of 4K broadcasting has been completed (Yes in S3212), the control unit 50 proceeds to step S3250 and executes a second channel search.

[0275] 20(c), before actually starting the second channel search for 2K broadcasts, the control unit 50 sets the first demodulation unit 20Ba for demodulation based on the ISDB-T standard for 2K broadcasts, and sets the decoding unit 40 for decoding based on the ISDB-T standard for 2K broadcasts (S3251). After completing these settings, the control unit 50 starts a channel search for 2K broadcasts.

[0276] The control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S3252). If searching of all physical channels to be searched has not been completed (No in S3252), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0277] First, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10B to select a predetermined physical channel (S3253). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10B (S3254).

[0278] If synchronization is not established (No in S3254), the program information of the 2K broadcast cannot be acquired, and the control unit 50 sets the next physical channel from among the search targets (S3270).

[0279] If synchronization is established (Yes in S3254), the control unit 50 acquires demodulation information and control information from the first demodulation unit 20Ba (S3255).

[0280] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S3256). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S3256), it does not acquire the 2K broadcast program information and sets the next physical channel (S3270). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S3256), it acquires the 2K broadcast program information from the decoding unit 40 (S3259). After acquiring the 2K broadcast program information, the control unit 50 sets the next physical channel from the search targets (S3270).

[0281] After step S3270, the control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S3252). If searching of all physical channels to be searched has not been completed (No in S3252), the control unit 50 executes steps S3253 to S3270 again. On the other hand, if searching of all physical channels to be searched has been completed (Yes in S3252), the control unit 50 ends the second channel search.

[0282] In the second modification of the third embodiment, the physical channels to be searched in the second channel search are also determined based on the synchronization information and the information on the in-band power value acquired during the first channel search. This makes it possible to reduce the number of physical channels to be searched in the second channel search. This makes it possible to prevent the search time from becoming long when performing channel searches corresponding to both 4K broadcasts and 2K broadcasts.

[0283] 3-5. Third Modification of Third Embodiment A channel search method according to Modification 3 of Embodiment 3 will be described. In Modification 3, an example will be described in which it is determined whether or not the in-band power value of a physical channel is equal to or greater than a predetermined threshold before determining whether synchronization has been established for 4K broadcasting.

[0284] Fig. 21 is a flowchart showing part of a channel search method according to Variation 3 of Embodiment 3. Steps S3311 to S3313 and S3318 to S3330 are the same as Steps S3211 to S3213 and S3218 to S3230 in Fig. 20(b) of Variation 2 of Embodiment 3.

[0285] In this third modification, in step S3314 of FIG. 21, the control unit 50 determines whether the in-band power value of a predetermined physical channel is equal to or greater than a predetermined threshold (S3314).

[0286] If the in-band power value of the predetermined physical channel is low and not equal to or greater than the predetermined threshold (No in S3314), the control unit 50 sets the next physical channel for searching for 4K broadcasts (S3330). On the other hand, if the in-band power value of the predetermined physical channel is equal to or greater than the predetermined threshold (Yes in S3314), the control unit 50 outputs a tuning instruction signal to the tuner unit 10B and determines whether synchronization has been established with the frequency of the predetermined physical channel (S3315).

[0287] If synchronization has not been established (No in S3315), the control unit 50 determines this physical channel as the search target for the second channel search and registers it in the storage unit 60 (S3316). Specifically, the control unit 50 registers in the storage unit 60 a physical channel whose in-band power value is equal to or greater than a predetermined threshold and for which synchronization has not been established. Then, the control unit 50 sets the next physical channel (S3330).

[0288] If synchronization is established (Yes in S3315), the control unit 50 acquires demodulation information and control information from the second demodulation unit 20Bb (S3317).

[0289] Next, the control unit 50 determines whether or not there is an error in the 4K broadcast layer based on the demodulation information (S3318). If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S3318), it does not acquire the 4K broadcast program information and sets the next physical channel (S3330). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S3318), it acquires the 4K broadcast program information from the decoding unit 40 (S3319). After acquiring the 4K broadcast program information, the control unit 50 sets the next physical channel for searching for the 4K broadcast (S3330).

[0290] After step S3330, the control unit 50 determines whether or not searching for all physical channels of 4K broadcasting is complete (S3312). If searching for all physical channels has not been completed (No in S3312), the control unit 50 executes steps S3312 to S3330 and searches for the next physical channel. On the other hand, if searching for all physical channels of 4K broadcasting is completed (Yes in S3312), the control unit 50 executes a second channel search.

[0291] In a third variation of the third embodiment, the physical channels to be searched in the second channel search are determined based on synchronization information and information related to in-band power values ​​acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from increasing when performing channel searches corresponding to both 4K broadcasting and 2K broadcasting. Furthermore, according to the third variation of the third embodiment, physical channels with large in-band power values ​​can be omitted from the second channel search, which is a search for 2K broadcasting, at an early stage.

[0292] (Fourth embodiment) [4-1. Configuration of receiving device] A description will be given of the configuration of a receiving device according to embodiment 4. The receiving device according to embodiment 4 receives 2K broadcast signals and 4K broadcast signals transmitted by the ISDB-T system, and searches a plurality of physical channels of these digital broadcasts.

[0293] FIG. 22 is a diagram showing a configuration of a receiving device 1C according to the fourth embodiment.

[0294] 22, the receiving device 1C has the same configuration as the receiving device 1 of the first embodiment, and includes a tuner unit 10, a demodulation unit 20, a decoding unit 40, a control unit 50, and a display unit 70. The control unit 50 includes a storage unit 60.

[0295] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and controls the tuner unit 10. The control unit 50 also outputs a channel selection instruction signal and a setting signal to the demodulation unit 20 and the decoding unit 40, respectively, and controls the demodulation unit 20 and the decoding unit 40.

[0296] An RF signal is input to the tuner unit 10 from the antenna 2. The tuner unit 10 selects a predetermined physical channel based on a channel selection instruction signal output from the control unit 50, converts the RF signal corresponding to the predetermined physical channel into an IF signal, and outputs the IF signal to the demodulation unit 20.

[0297] The demodulation unit 20 performs demodulation processing on the IF signal output from the tuner unit 10. The demodulation unit 20 performs the demodulation processing based on the tuning instruction signal and setting signal output from the control unit 50, and outputs the demodulated signal to the decoding unit 40. The demodulation unit 20 also outputs demodulation information (for example, synchronization information, C / N information, error information) and control information obtained by the demodulation processing to the control unit 50. The demodulation unit 20 of this embodiment also performs error correction processing corresponding to each of 2K broadcasting and 4K broadcasting.

[0298] The decoding unit 40 performs a decoding process on the signal output from the demodulation unit 20. The decoding unit 40 performs the above-mentioned decoding process based on the channel selection instruction signal and setting signal output from the control unit 50, and outputs the decoded video signal to the display unit 70. The decoding unit 40 also outputs the program information obtained by the decoding process to the control unit 50.

[0299] The display unit 70 is a display device such as a display, etc. The display unit 70 displays an image based on the video signal output from the decoding unit 40.

[0300] The demodulation unit 20 includes an AD conversion unit 21, a time axis processing unit 22, an FFT unit 23, a carrier synchronization unit 24, an equalization unit 25, a TMCC decoding unit 26, a 4K broadcast control information decoding unit 27, a deinterleaving unit 28, a first error correction processing unit 31, a second error correction processing unit 32, and an output selection unit 33 (see FIG. 3). Note that the demodulation unit 20 may include a separation unit 29 for separating the 4K broadcast signal from the broadcast signal of the physical channel, similar to FIG. 4 of the first embodiment.

[0301] The receiving device 1C of this embodiment comprises an AD conversion unit 21, a carrier synchronization unit 24, an equalization unit 25, a deinterleaving unit 28, a first error correction processing unit 31 that performs a first error correction processing on the signal output from the deinterleaving unit 28, and a second error correction processing unit 32 that performs a second error correction processing, and the first error correction processing performed by the first error correction processing unit 31 and the second error correction processing performed by the second error correction processing unit 32 are different.

[0302] In this way, by including the first error correction processing unit 31 and the second error correction processing unit 32, the receiving device 1C can perform error correction processing for the broadcast signals of 2K broadcasts and the broadcast signals of 4K broadcasts, which have different error correction processing methods. This allows, for example, a first channel search for 2K broadcasts to be performed, and physical channels to be searched in a second channel search for 4K broadcasts to be determined during the first channel search. Then, the second channel search can be performed only on the physical channels that are searched in the second channel search. This reduces the number of physical channels to be searched in the second channel search, thereby preventing the search time from becoming too long.

[0303] [4-2. How to search for channels] A channel search method according to the fourth embodiment will be described.

[0304] In this embodiment, an example will be described in which a first broadcast of a plurality of digital broadcasts is a 2K broadcast, a second broadcast is a 4K broadcast, and the 2K broadcast and the 4K broadcast are transmitted using a three-layer system or an LDM system. Also, in this embodiment, an example will be described in which the first channel search and the second channel search are performed consecutively on one physical channel, rather than completing the first channel search on all physical channels and then performing the second channel search on the physical channel that was the search target.

[0305] These digital broadcasting physical channels are designed to be able to contain both 2K broadcast signals (first broadcast signals) and 4K broadcast signals (second broadcast signals), which use different error correction processing methods. In other words, a single physical channel may contain both 2K and 4K broadcast signals simultaneously, or it may contain only one of them.

[0306] FIG. 23 is a flowchart showing a channel search method according to the fourth embodiment.

[0307] As shown in Fig. 23, the channel search method according to the fourth embodiment performs a first channel search and a second channel search in one routine. Specifically, this channel search method includes performing a first channel search for 2K broadcasting on one physical channel, determining a physical channel to be searched in a second channel search for 4K broadcasting during the first channel search, and performing the second channel search on the physical channel that has been searched in the second channel search. In the fourth embodiment, this one routine is performed for each of a plurality of physical channels.

[0308] First, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting has been completed (S4011). If searching for all physical channels has not been completed (No in S4011), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0309] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and selects a predetermined physical channel (S4012). Next, the control unit 50 sets the demodulation unit 20 to demodulation for 2K broadcasting, and sets the decoding unit 40 to decoding for 2K broadcasting (S4013).

[0310] The control unit 50 determines whether or not synchronization has been established with the frequency of a predetermined physical channel in the tuner unit 10 (S4014).

[0311] If synchronization is not established (No at S4014), the control unit 50 determines that the specified physical channel does not exist at the current position of the receiving device 1C, and sets the next physical channel for searching for 2K broadcasts (S4030).

[0312] If synchronization is established (Yes in S4014), the control unit 50 acquires demodulation information and control information from the demodulation unit 20 (S4015). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcast with which synchronization is established during the first channel search.

[0313] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S4016). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S4016), it does not acquire the 2K broadcast program information and proceeds to the next step S4018. If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S4016), it acquires the 2K broadcast program information from the decoding unit 40 (S4017) and proceeds to the next step S4018.

[0314] In step S4018, the control unit 50 determines whether or not this physical channel includes a 4K broadcast (S4018).

[0315] If the physical channel does not include 4K broadcasting (No in S4018), the control unit 50 does not determine the search target for the second channel search, and sets the next physical channel for searching for 2K broadcasting (S4030).If the physical channel includes 4K broadcasting (Yes in S4018), the control unit 50 sets this physical channel as the search target for the second channel search, and proceeds to the next step S4054.

[0316] The control unit 50 sets the demodulation unit 20 to demodulation for 4K broadcasting, and also sets the decoding unit 40 to decode for 4K broadcasting (S4054). Next, the control unit 50 acquires demodulation information and control information related to the 4K broadcasting from the demodulation unit 20 (S4055). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcasting with which synchronization was established during the first channel search.

[0317] Next, the control unit 50 determines whether or not there is an error in the 4K broadcast layer based on the demodulation information (S4056). If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S4056), it sets the next physical channel without acquiring the 4K broadcast program information (S4030). If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S4056), it acquires the 4K broadcast program information from the decoding unit 40 (S4059).

[0318] When the acquisition of the 4K broadcast program information is completed, the control unit 50 sets the next physical channel (S4030).

[0319] After step S4030, the control unit 50 determines whether or not the search for all of the physical channels has been completed (S4011).

[0320] If the control unit 50 has not finished searching all of the physical channels (No in S4011), it executes steps S4012 to S4059 again. On the other hand, if the control unit 50 has finished searching all of the physical channels (Yes in S4011), it ends the channel search by the receiving device 1C.

[0321] In the channel search method of the fourth embodiment, the physical channels to be searched in the second channel search are determined based on the control information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting.

[0322] Although the above example shows step S4013 being executed between step S4012 and step S4014, the present invention is not limited to this, and step S4013 may be executed between step S4011 and step S4012, or before step S4017. Furthermore, if step S4054 is not executed in one routine and the demodulation settings and decoding settings are not changed, step S4013 in the next routine may be omitted.

[0323] Also, although the above example shows that the 4K broadcast decoding setting in step S4054 is performed between steps S4018 and S4055, this is not limited thereto, and the 4K broadcast decoding setting may also be performed between steps S4055 and S4059.

[0324] 4-3. First Modification of Fourth Embodiment A description will be given of a channel search method according to Modification 1 of Embodiment 4. In Modification 1, an example will be described in which, when it is determined that there is an error in the 2K broadcast layer, the physical channel is switched and a search for the next physical channel is performed without checking whether or not there is a 4K broadcast.

[0325] FIG. 24 is a flowchart showing a channel search method according to the fourth embodiment.

[0326] The control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulated information (S4116).

[0327] If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S4116), it does not acquire the 2K broadcast program information and sets the next physical channel for searching for the 2K broadcast (S4130). 4K broadcast uses a modulation method with a more efficient transmission rate than 2K broadcast, and therefore has weaker error resistance than 2K broadcast. Therefore, if there is an error in the 2K broadcast, there is a high possibility that there will also be an error in the 4K broadcast. Therefore, in this modified example, if there is an error in the 2K broadcast layer, the next physical channel is searched for without checking whether there is a 4K broadcast.

[0328] On the other hand, if the control unit 50 determines that there is no error in the 2K broadcast layer (No in S4116), it acquires the 2K broadcast program information from the decoding unit 40 (S4117) and proceeds to the next step S4118.

[0329] In the first modification of the fourth embodiment, the physical channels to be searched in the second channel search are also determined based on the control information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming too long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts.

[0330] 4-4. Second Modification of the Fourth Embodiment A channel search method according to the second modification of the fourth embodiment will be described.

[0331] In this Modification 2, an example will be described in which a first broadcast of a plurality of digital broadcasts is a 4K broadcast, a second broadcast is a 2K broadcast, and the 2K broadcast and the 4K broadcast are transmitted using a three-layer system or an LDM system. Also, in this Modification 2, as in the fourth embodiment, an example will be described in which the first channel search and the second channel search are performed consecutively on one physical channel, rather than completing the first channel search on all physical channels and then performing the second channel search on the physical channel that was the search target.

[0332] FIG. 25 is a flowchart showing a channel search method according to the second modification of the fourth embodiment.

[0333] As shown in Fig. 25, the channel search method according to the second modification of the fourth embodiment performs a first channel search and a second channel search in one routine. Specifically, this channel search method includes performing a first channel search for 4K broadcasting on one physical channel, determining a physical channel to be searched in a second channel search for 2K broadcasting during the first channel search, and performing the second channel search on the physical channel that was searched in the second channel search. In this second modification, this single routine is also performed on multiple physical channels.

[0334] First, the control unit 50 determines whether or not searching for all physical channels of 4K broadcasting has been completed (S4211). If searching for all physical channels has not been completed (No in S4211), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0335] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and selects a predetermined physical channel (S4212). Next, the control unit 50 sets the demodulation unit 20 to demodulation for 4K broadcasting, and sets the decoding unit 40 to decoding for 4K broadcasting (S4213).

[0336] The control unit 50 determines whether or not synchronization has been established with the frequency of a predetermined physical channel in the tuner unit 10 (S4214).

[0337] If synchronization is not established (No in S4214), the control unit 50 sets the next physical channel for searching for 4K broadcasts (S4230). In this second modification, physical channels for which synchronization is not established as 4K broadcasts are not compliant with the ISDB-T standard or the ISDB-T standard signal is weak or non-existent, and therefore are removed from the search targets for 2K broadcasts, which is the second channel search.

[0338] If synchronization is established (Yes in S4214), the control unit 50 determines whether or not the physical channel with which synchronization is established includes a 4K broadcast based on the control information (S4215). The control information includes information indicating whether or not the digital broadcast signal being selected includes a 4K broadcast signal. The control information is included in the TMCC information or AC information of the 2K broadcast signal.

[0339] If the physical channel does not include 4K broadcasting (No in S4215), the control unit 50 proceeds to the next step S4255 to perform a second channel search.

[0340] If this physical channel includes 4K broadcasting (Yes in S4215), the control unit 50 acquires demodulation information and control information other than the above-mentioned TMCC information or AC information from the demodulation unit 20 (S4216). The demodulation information and control information are acquired from the ISDB-T signal with which synchronization was established during the first channel search.

[0341] The control unit 50 determines whether or not there is an error in the 4K broadcast layer based on the demodulation information (S4217). If the control unit 50 determines that there is an error in the 4K broadcast layer (Yes in S4217), it does not acquire the 4K broadcast program information and proceeds to the next step S4255. If the control unit 50 determines that there is no error in the 4K broadcast layer (No in S4217), it acquires the 4K broadcast program information from the decoding unit 40 (S4218) and proceeds to the next step S4254.

[0342] The control unit 50 sets the demodulation unit 20 to demodulation for 2K broadcasting, and also sets the decoding unit 40 to decode for 2K broadcasting (S4254). Next, the control unit 50 acquires demodulation information and control information related to the 2K broadcasting from the demodulation unit 20 (S4255). The demodulation information and control information are acquired from the ISDB-T signal with which synchronization was established during the first channel search.

[0343] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S4256). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S4256), it sets the next physical channel without acquiring the 2K broadcast program information (S4230). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S4256), it acquires the 2K broadcast program information from the decoding unit 40 (S4259). Note that, although an example has been shown above in which the 2K broadcast decoding setting in step S4254 is performed between steps S4218 and S4255, the present invention is not limited to this, and the 2K broadcast decoding setting may be performed between steps S4255 and S4259.

[0344] When the acquisition of the 2K broadcast program information is completed, the control unit 50 sets the next physical channel (S4230).

[0345] After step S4230, the control unit 50 determines whether or not the search for all of the physical channels has been completed (S4211).

[0346] If the control unit 50 has not finished searching all of the multiple physical channels (No in S4211), it executes steps S4212 to S4260 again. On the other hand, if the control unit 50 has finished searching all of the multiple physical channels (Yes in S4211), it ends the channel search by the receiving device 1C.

[0347] In the second modification of the fourth embodiment, the physical channels to be searched in the second channel search are also determined based on the control information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming too long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts.

[0348] (Embodiment 5) [5-1. Configuration of receiving device] The following describes the configuration of a receiving device according to embodiment 5. The receiving device according to embodiment 5 receives a 2K broadcast signal transmitted by the ISDB-T standard and a 4K broadcast signal transmitted by a new broadcast standard, and searches a plurality of physical channels of these digital broadcasts.

[0349] FIG. 26 is a diagram showing a configuration of a receiving device 1D according to the fifth embodiment.

[0350] As shown in Fig. 26, the receiving device 1D has a configuration similar to that of the receiving device 1A of the second embodiment, and includes a tuner unit 10, a demodulation unit 20A, a decoding unit 40, a control unit 50, and a display unit 70. The control unit 50 includes a storage unit 60. Fig. 26 also shows an antenna 2 connected to the receiving device 1D.

[0351] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and controls the tuner unit 10. The control unit 50 also outputs a channel selection instruction signal and a setting signal to the demodulation unit 20A and the decoding unit 40, respectively, and controls the demodulation unit 20A and the decoding unit 40.

[0352] An RF signal is input to the tuner unit 10 from the antenna 2. The tuner unit 10 selects a predetermined physical channel based on a tuning instruction signal output from the control unit 50, converts the RF signal corresponding to the predetermined physical channel into an IF signal, and outputs the IF signal to the demodulation unit 20A.

[0353] The demodulation unit 20A performs demodulation processing on the IF signal output from the tuner unit 10. The demodulation unit 20A performs the demodulation processing based on the tuning instruction signal and setting signal output from the control unit 50, and outputs the demodulated signal to the decoding unit 40. The demodulation unit 20A also outputs demodulation information (for example, synchronization information, C / N information, error information) and control information obtained by the demodulation processing to the control unit 50. The demodulation unit 20A of this embodiment performs error correction processing corresponding to each of 2K broadcasting and 4K broadcasting.

[0354] The decoding unit 40 performs a decoding process on the signal output from the demodulation unit 20A. The decoding unit 40 performs the above-mentioned decoding process based on the channel selection instruction signal and setting signal output from the control unit 50, and outputs the decoded video signal to the display unit 70. The decoding unit 40 also outputs the program information obtained by the decoding process to the control unit 50.

[0355] The display unit 70 is a display device such as a display, etc. The display unit 70 displays an image based on the video signal output from the decoding unit 40.

[0356] The demodulation unit 20A includes an AD conversion unit 21, a first demodulation unit 20Aa, a second demodulation unit 20Ab, and an output selection unit 33 (see FIG. 12). The first demodulation unit 20Aa performs demodulation processing compatible with ISDB-T, and the second demodulation unit 20Ab performs demodulation processing compatible with a new broadcasting system.

[0357] The first demodulation unit 20Aa includes a time axis processing unit 22a, an FFT unit 23a, a carrier synchronization unit 24a, an equalization unit 25a, a TMCC decoding unit 26a, a deinterleaving unit 28a, and a first error correction processing unit 31a. The second demodulation unit 20Ab includes a time axis processing unit 22b, an FFT unit 23b, a carrier synchronization unit 24b, an equalization unit 25b, a TMCC decoding unit 26b, a deinterleaving unit 28b, and a second error correction processing unit 32b.

[0358] The receiving device 1D of this embodiment comprises an AD conversion unit 21, carrier synchronization units 24a, 24b, equalization units 25a, 25b, deinterleaving units 28a, 28b, a first error correction processing unit 31a that performs a first error correction process on the signal output from the deinterleaving unit 28a, and a second error correction processing unit 32b that performs a second error correction process on the signal output from the deinterleaving unit 28b, and the first error correction process performed by the first error correction processing unit 31a is different from the second error correction process performed by the second error correction processing unit 32b.

[0359] In this way, by having the receiving device 1D with the first error correction processing unit 31a and the second error correction processing unit 32b, it is possible to perform error correction processing on the broadcast signals of 2K broadcasting and 4K broadcasting, which have different error correction processing methods.

[0360] [5-2. How to search for channels] A channel search method according to the fifth embodiment will be described.

[0361] In this embodiment, an example will be described in which a first broadcast of a plurality of digital broadcasts is a 2K broadcast, a second broadcast is a 4K broadcast, the 2K broadcast is transmitted in the ISDB-T format, and the 4K broadcast is transmitted in a new broadcast format. Also, in this embodiment, an example will be described in which a first channel search and a second channel search are performed consecutively on one physical channel, rather than a first channel search being performed on all physical channels after the first channel search is completed.

[0362] These digital broadcasting physical channels are designed to be capable of containing either a 2K broadcast signal (first broadcast signal) or a 4K broadcast signal (second broadcast signal), which have different error correction processing methods. In other words, each of the multiple physical channels contains either a 2K broadcast signal or a 4K broadcast signal.

[0363] FIG. 27 is a flowchart showing a channel search method according to the fifth embodiment.

[0364] As shown in Fig. 27, the channel search method according to the fifth embodiment performs a first channel search and a second channel search in one routine. Specifically, this channel search method includes performing a first channel search for 2K broadcasting on one physical channel, determining a physical channel to be searched in a second channel search for 4K broadcasting during the first channel search, and performing the second channel search on the physical channel that has been searched in the second channel search. In the fifth embodiment, this one routine is performed for each of a plurality of physical channels.

[0365] First, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting has been completed (S5011). If searching for all physical channels has not been completed (No in S5011), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0366] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and selects a predetermined physical channel (S5012). Next, the control unit 50 sets the demodulation unit 20A to demodulation for 2K broadcasting, and sets the decoding unit 40 to decoding for 2K broadcasting (S5013).

[0367] The control unit 50 determines whether or not synchronization has been established with the frequency of a predetermined physical channel in the tuner unit 10 (S5014).

[0368] If synchronization is established (Yes in S5014), the control unit 50 acquires demodulation information and control information from the demodulation unit 20A (S5015). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcast with which synchronization is established during the first channel search.

[0369] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S5016). If the control unit 50 determines that there is an error in the layer of the 2K broadcast (Yes in S5016), it does not acquire the program information of the 2K broadcast, and sets the next physical channel for searching the 2K broadcast (S5030). If the control unit 50 determines that there is no error in the layer of the 2K broadcast (No in S5016), it acquires the program information of the 2K broadcast from the decoding unit 40 (S5019), and sets the next physical channel for searching the 2K broadcast (S5030).

[0370] On the other hand, if synchronization has not been established (No in S5014), it is determined that the predetermined physical channel does not include 2K broadcasts, and the process proceeds to step S5051 for searching for 4K broadcasts. That is, the currently set predetermined physical channel is determined as the search target for searching for 4K broadcasts.

[0371] In step S5051, the control unit 50 sets the demodulation unit 20A to demodulation settings for 4K broadcasting, and also sets the decoding unit 40 to decoding settings for 4K broadcasting (S5051).

[0372] The control unit 50 determines whether or not synchronization has been established with the frequency of a predetermined physical channel in the tuner unit 10 (S5052).

[0373] If synchronization is not established (No in S5052), it is determined that the specified physical channel does not include 4K broadcasting, and the next physical channel is set to search for 2K broadcasting (S5030).

[0374] If synchronization is established (Yes in S5052), the control unit 50 acquires demodulation information and control information from the demodulation unit 20A (S5053). The demodulation information and control information are acquired from the broadcast signal of the 4K broadcast with which synchronization is established during the second channel search.

[0375] Next, the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulation information (S5054). If the control unit 50 determines that there is an error in the layer of the 4K broadcast (Yes in S5054), it does not acquire the program information of the 4K broadcast, and sets the next physical channel for searching in the 2K broadcast (S5030). If the control unit 50 determines that there is no error in the layer of the 4K broadcast (No in S5054), it acquires the program information of the 4K broadcast from the decoding unit 40 (S5059), and sets the next physical channel for searching for the 4K broadcast (S5030).

[0376] After step S5030, the control unit 50 determines whether or not the search for all of the physical channels has been completed (S5011).

[0377] If the control unit 50 has not yet completed searching all of the physical channels (No in S5011), it executes steps S5012 to S5059 again. On the other hand, if the control unit 50 has completed searching all of the physical channels (Yes in S5011), it ends the channel search by the receiving device 1D.

[0378] In the channel search method of the fifth embodiment, the physical channels to be searched in the second channel search are determined based on the synchronization establishment information acquired during the first channel search. This makes it possible to reduce the number of physical channels to be searched in the second channel search. This makes it possible to prevent the search time from becoming long when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting.

[0379] Although the above example shows step S5013 being executed between step S5012 and step S5014, the present invention is not limited to this, and step S5013 may be executed between step S5011 and step S5012. Furthermore, if step S5051 is not executed within one routine, i.e., if the demodulation settings and decoding settings are not changed, step S5013 in the next routine may be omitted.

[0380] 5-3. First Modification of the Fifth Embodiment A channel search method according to the first modification of the fifth embodiment will be described.

[0381] In this modification 1, an example will be described in which a first broadcast of a plurality of digital broadcasts is a 4K broadcast, a second broadcast is a 2K broadcast, the 4K broadcast is transmitted in a new broadcasting format, and the 2K broadcast is transmitted in the ISDB-T format. Also in this modification 1, an example will be described in which a first channel search and a second channel search are performed consecutively for one physical channel.

[0382] The physical channels of these digital broadcasts are designed to be capable of containing either a 4K broadcast signal (first broadcast signal) or a 2K broadcast signal (second broadcast signal), which have different error correction processing methods.

[0383] FIG. 28 is a flowchart showing a channel search method according to the first modification of the fifth embodiment.

[0384] As shown in Fig. 28, the channel search method according to the first modification of the fifth embodiment performs a first channel search and a second channel search in one routine. Specifically, this channel search method includes performing a first channel search for 4K broadcasting on one physical channel, determining a physical channel to be searched for in a second channel search for 2K broadcasting during the first channel search, and performing the second channel search on the physical channel that was searched for in the second channel search. In this first modification, this single routine is also performed for each of a plurality of physical channels.

[0385] First, the control unit 50 determines whether or not searching for all physical channels of 4K broadcasting has been completed (S5111). If searching for all physical channels has not been completed (No in S5111), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0386] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and selects a predetermined physical channel (S5112). Next, the control unit 50 sets the demodulation unit 20A to demodulation settings for 4K broadcasting, and sets the decoding unit 40 to decoding settings for 4K broadcasting (S5113).

[0387] The control unit 50 determines whether or not synchronization has been established with the frequency of a predetermined physical channel in the tuner unit 10 (S5114).

[0388] If synchronization is established (Yes in S5114), the control unit 50 acquires demodulation information and control information from the demodulation unit 20A (S5115). The demodulation information and control information are acquired from the broadcast signal of the 4K broadcast with which synchronization is established during the first channel search.

[0389] Next, the control unit 50 determines whether or not there is an error in the layer of the 4K broadcast based on the demodulation information (S5116). If the control unit 50 determines that there is an error in the layer of the 4K broadcast (Yes in S5116), it does not acquire the program information of the 4K broadcast and sets the next physical channel for searching the 4K broadcast (S5130). If the control unit 50 determines that there is no error in the layer of the 4K broadcast (No in S5116), it acquires the program information of the 4K broadcast from the decoding unit 40 (S5119) and sets the next physical channel for searching the 4K broadcast (S5130).

[0390] On the other hand, if synchronization has not been established (No in S5114), it is determined that the predetermined physical channel does not include 4K broadcasts, and the process proceeds to step S5151 to search for 2K broadcasts. That is, the currently set predetermined physical channel is determined as the search target for searching for 2K broadcasts.

[0391] In step S5151, the control unit 50 sets the demodulation unit 20A to demodulation for 2K broadcasting, and sets the decoding unit 40 to decoding for 2K broadcasting (S5151).

[0392] The control unit 50 determines whether or not synchronization has been established with the frequency of a predetermined physical channel in the tuner unit 10 (S5152).

[0393] If synchronization is not established (No in S5152), it is determined that the predetermined physical channel does not include 2K broadcasting, and the next physical channel is set to search for 4K broadcasting (S5130).

[0394] If synchronization is established (Yes in S5152), the control unit 50 acquires demodulation information and control information from the demodulation unit 20A (S5153). The demodulation information and control information are acquired from the 2K broadcast signal with which synchronization is established during the second channel search.

[0395] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S5154). If the control unit 50 determines that there is an error in the layer of the 2K broadcast (Yes in S5154), it does not acquire the program information of the 2K broadcast, and sets the next physical channel for searching in the 4K broadcast (S5130). If the control unit 50 determines that there is no error in the layer of the 2K broadcast (No in S5154), it acquires the program information of the 2K broadcast from the decoding unit 40 (S5159), and sets the next physical channel for searching in the 4K broadcast (S5130).

[0396] After step S5130, the control unit 50 determines whether or not the search for all of the plurality of physical channels has been completed (S5111).

[0397] If the control unit 50 has not finished searching all of the multiple physical channels (No in S5111), it executes steps S5112 to S5159 again. On the other hand, if the control unit 50 has finished searching all of the multiple physical channels (Yes in S5111), it ends the channel search by the receiving device 1D.

[0398] In the channel search method of the first modification of the fifth embodiment, the physical channels to be searched in the second channel search are determined based on the synchronization establishment information acquired during the first channel search. This makes it possible to reduce the number of physical channels to be searched in the second channel search. This makes it possible to prevent the search time from becoming long when performing channel searches corresponding to both 4K broadcasts and 2K broadcasts.

[0399] While the example above shows step S5113 being executed between step S5112 and step S5114, the present invention is not limited to this, and step S5113 may be executed between step S5111 and step S5112. Furthermore, if step S5151 is not executed within one routine, i.e., if the demodulation settings and decoding settings are not changed, step S5113 in the next routine may be omitted.

[0400] (Embodiment 6) [6-1. Configuration of receiving device] The following describes the configuration of a receiving device according to embodiment 6. The receiving device according to embodiment 6 has a configuration capable of receiving 2K broadcasts and 4K broadcasts in a three-layer system or an LDM system, and a configuration capable of receiving 2K broadcasts in the ISDB-T system and 4K broadcasts in a new broadcasting system.

[0401] FIG. 29 is a diagram showing a configuration of a receiving device 1E according to the sixth embodiment.

[0402] 29, the receiving device 1E includes a tuner unit 10, a demodulation unit 20E, a decoding unit 40, a control unit 50, and a display unit 70. The control unit 50 includes a storage unit 60.

[0403] The control unit 50 outputs a channel selection instruction signal to the tuner unit 10 and controls the tuner unit 10. The control unit 50 also outputs a channel selection instruction signal and a setting signal to the demodulation unit 20E and the decoding unit 40, respectively, and controls the demodulation unit 20E and the decoding unit 40.

[0404] An RF signal is input to the tuner unit 10 from the antenna 2. The tuner unit 10 selects a predetermined physical channel based on a tuning instruction signal output from the control unit 50, converts the RF signal corresponding to the predetermined physical channel into an IF signal, and outputs the IF signal to the demodulation unit 20E.

[0405] The demodulation unit 20E performs demodulation processing on the IF signal output from the tuner unit 10. The demodulation unit 20E performs the demodulation processing based on the tuning instruction signal and setting signal output from the control unit 50, and outputs the demodulated signal to the decoding unit 40. The demodulation unit 20E also outputs demodulation information (for example, synchronization information, C / N information, error information) and control information obtained by the demodulation processing to the control unit 50. The demodulation unit 20E of this embodiment also performs error correction processing corresponding to each of 2K broadcasting and 4K broadcasting.

[0406] The decoding unit 40 performs a decoding process on the signal output from the demodulation unit 20E. The decoding unit 40 performs the above-mentioned decoding process based on the channel selection instruction signal and setting signal output from the control unit 50, and outputs the decoded video signal to the display unit 70. The decoding unit 40 also outputs the program information obtained by the decoding process to the control unit 50.

[0407] The display unit 70 is a display device such as a display, etc. The display unit 70 displays an image based on the video signal output from the decoding unit 40.

[0408] FIG. 30 is a diagram showing a configuration of a demodulation unit 20E of a receiving device 1E according to the sixth embodiment.

[0409] 30 includes an AD conversion unit 21, a first demodulation unit 20Ea, a second demodulation unit 20Eb, and an output selection unit 33. The first demodulation unit 20Ea is a demodulation unit that supports the three-layer system, and the second demodulation unit 20Eb is a demodulation unit that supports a new broadcasting system.

[0410] The first demodulation unit 20Ea includes a time axis processing unit 22, an FFT unit 23, a carrier synchronization unit 24, an equalization unit 25, a TMCC decoding unit 26, a 4K broadcast control information decoding unit 27, a deinterleaving unit 28, a first error correction processing unit 31, and a second error correction processing unit 32. The signals output from the first error correction processing unit 31 and the second error correction processing unit 32 are input to an output selection unit 33.

[0411] The second demodulation unit 20Eb includes a time axis processing unit 22b, an FFT unit 23b, a carrier synchronization unit 24b, an equalization unit 25b, a TMCC decoding unit 26b, a deinterleaving unit 28b, and a second error correction processing unit 32b. The signal output from the second error correction processing unit 32b is input to an output selection unit 33. The first error correction processing unit 31 and the second error correction processing unit 32 perform different error correction processing. The first error correction processing unit 31 and the second error correction processing unit 32b perform different error correction processing. The second error correction processing unit 32 and the second error correction processing unit 32b may perform the same error correction processing.

[0412] Next, another configuration of the demodulation unit 20E according to the sixth embodiment will be described.

[0413] FIG. 31 is a diagram showing another configuration of the demodulation unit 20E according to the sixth embodiment.

[0414] 31 includes an AD conversion unit 21, a first demodulation unit 20Ea, a second demodulation unit 20Eb, and an output selection unit 33. The first demodulation unit 20Ea is a demodulation unit compatible with the LDM system, and the second demodulation unit 20Eb is a demodulation unit compatible with a new broadcasting system. In the LDM system, the 4K broadcast signal is superimposed as power on the 2K broadcast signal, so it is necessary to separate the 2K broadcast from the 4K broadcast.

[0415] For this reason, the first demodulation unit 20Ea includes a separation unit 29 for separating the 4K broadcast signal from the broadcast signal of the physical channel. For example, the separation unit 29 creates a replica of the 2K broadcast signal from the signal deinterleaved by the deinterleaving unit 28, subtracts the 2K broadcast signal, performs inverse correction based on the superimposed level, and extracts the 4K broadcast signal. The signal extracted by the separation unit 29 is output to the second error correction processing unit 32.

[0416] The receiving device 1E of this embodiment comprises an AD conversion unit 21, carrier synchronization units 24, 24b, equalization units 25, 25b, deinterleaving units 28, 28b, a first error correction processing unit 31 that performs a first error correction processing on the signal output from the deinterleaving unit 28, a second error correction processing unit 32 that performs a second error correction processing on the signal output from the deinterleaving unit 28b, and a second error correction processing unit 32b that performs a second error correction processing on the signal output from the deinterleaving unit 28b, and the first error correction processing performed by the first error correction processing unit 31, the second error correction processing performed by the second error correction processing unit 32, and the second error correction processing performed by the second error correction processing unit 32b are different.

[0417] [6-2. How to search for channels] A channel search method according to the sixth embodiment will be described.

[0418] In this embodiment, an example will be described in which a first broadcast among a plurality of digital broadcasts is a 2K broadcast, a second broadcast is a 4K broadcast, and the 2K broadcast and the 4K broadcast are transmitted using a three-layer system, an LDM system, an ISDB-T system, and a new broadcast system.

[0419] These digital broadcasting physical channels are designed to be able to contain both 2K broadcast signals (first broadcast signals) and 4K broadcast signals (second broadcast signals), which use different error correction processing methods. In other words, a single physical channel may contain both 2K and 4K broadcast signals simultaneously, or it may contain only one of them.

[0420] In this embodiment, among the broadcast signals of 4K broadcasting, the broadcast signal transmitted using the three-layer method or the LDM method may be referred to as one broadcast signal, and the broadcast signal transmitted using the new broadcast method may be referred to as the other broadcast signal.

[0421] Fig. 32A is a flowchart showing a part of a channel search method according to Embodiment 6. Fig. 32B is a flowchart showing another part of a channel search method according to Embodiment 6.

[0422] 32A, the channel search method according to the sixth embodiment includes step S6010 of performing a first channel search, and step S6050 of performing a channel search of one broadcast signal and step S6050b of performing a channel search of the other broadcast signal after step S6010. In this embodiment, the second channel search is performed by a channel search of one broadcast signal and a channel search of the other broadcast signal. The multiple physical channels include one physical channel that is the search target of the channel search of one broadcast signal and another physical channel that is the search target of the channel search of the other broadcast signal.

[0423] This channel search method also includes performing a first channel search for 2K broadcasting (first broadcast signal) on multiple physical channels, determining physical channels to be searched in a channel search of one and other broadcast signals for 4K broadcasting (second broadcast signal) during the first channel search, and performing a channel search of the one and other broadcast signals on the physical channels that have been searched in the channel search of the one and other broadcast signals. Below, a detailed flow of step S6010 is described in Figure 32A, and a detailed flow of steps S6050 and S6050b is described in Figure 32B.

[0424] 32A(b), before actually starting a first channel search for 2K broadcasts, the control unit 50 performs 2K broadcast demodulation settings on the demodulation unit 20E and performs 2K broadcast decoding settings on the decoding unit 40 (S6011). After completing these settings, the control unit 50 starts a 2K broadcast channel search.

[0425] First, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting has been completed (S6012). If searching for all physical channels has not been completed (No in S6012), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0426] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6013). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6014).

[0427] If synchronization has not been established (No in S6014), the control unit 50 sets this physical channel as the other physical channel and determines this other physical channel as the search target for the channel search for the other 4K broadcast in the second channel search. The control unit 50 registers the other physical channel in the storage unit 60 (S6022) and sets the next physical channel for searching for 2K broadcast (S6030).

[0428] If synchronization is established (Yes in S6014), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6015). The demodulation information and control information are acquired from the 2K broadcast signal with which synchronization is established during the first channel search.

[0429] The control unit 50 determines, based on the control information, whether or not the synchronized physical channel includes a 4K broadcast (S6016). If the synchronized physical channel includes a 4K broadcast (Yes in S6016), the control unit 50 sets the synchronized physical channel as one of the physical channels and determines the one of the physical channels as the search target for the channel search of one of the broadcast signals in the second channel search. The control unit 50 registers the one of the physical channels in the storage unit 60 (S6017) and proceeds to the next step, S6018. If the synchronized physical channel does not include a 4K broadcast (No in S6016), the one of the physical channels is not registered, and the process proceeds to the next step, S6018.

[0430] Next, the control unit 50 determines whether or not there is an error in the layer of the 2K broadcast based on the demodulation information (S6018). If the control unit 50 determines that there is an error in the layer of the 2K broadcast (Yes in S6018), it does not acquire the program information of the 2K broadcast and sets the next physical channel (S6030). If the control unit 50 determines that there is no error in the layer of the 2K broadcast (No in S6018), it acquires the program information of the 2K broadcast from the decoding unit 40 (S6019). After acquiring the program information of the 2K broadcast, the control unit 50 sets the next physical channel for searching for the 2K broadcast (S6030).

[0431] After step S6030, the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting is complete (S6012). If searching for all physical channels has not been completed (No in S6012), the control unit 50 executes steps S6012 to S6030 and searches for the next physical channel. If searching for all physical channels of 2K broadcasting is completed (Yes in S6012), the control unit 50 proceeds to step S6050 and executes a second channel search.

[0432] The second channel search is performed by performing a channel search for one broadcast signal and a channel search for the other broadcast signal. Below, we will explain an example in which a channel search for one 4K broadcast shown in (a) of Figure 32B is performed, and then a channel search for the other 4K broadcast shown in (b) of Figure 32B is performed.

[0433] 32B(a), before actually starting a channel search for one 4K broadcast, the control unit 50 performs demodulation settings for one broadcast signal on the demodulation unit 20E and performs decode settings for one broadcast signal on the decoding unit 40 (S6051). After completing these settings, the control unit 50 starts a channel search for one 4K broadcast.

[0434] The control unit 50 determines whether or not the search of one of the physical channels to be searched has been completed (S6052). If the search of one of the physical channels to be searched has not been completed (No in S6052), the control unit 50 starts a channel search for a specific physical channel from among the one of the physical channels to be searched.

[0435] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6053). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6054).

[0436] If synchronization is not established (No in S6054), the control unit 50 cannot acquire 4K broadcast program information, and therefore sets the next physical channel from among the search targets (S6070).

[0437] If synchronization is established (Yes in S6054), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6055). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0438] Next, the control unit 50 determines whether or not there is an error in the layer of one of the broadcast signals based on the demodulation information (S6056). If the control unit 50 determines that there is an error in the layer of one of the broadcast signals (Yes in S6056), it does not acquire the program information of one of the broadcast signals and sets the next physical channel (S6070). If the control unit 50 determines that there is no error in the layer of one of the broadcast signals (No in S6056), it acquires the program information of one of the broadcast signals from the decoding unit 40 (S6059). After acquiring the program information of one of the broadcast signals, the control unit 50 sets the next physical channel from among the search targets (S6070).

[0439] After step S6070, the control unit 50 determines whether or not the search of one of the physical channels to be searched has been completed (S6052).

[0440] If the control unit 50 has not yet completed searching one of the physical channels to be searched (No in S6052), it executes steps S6053 to S6070 again. If the control unit 50 has completed searching one of the physical channels to be searched (Yes in S6052), it ends the channel search for one 4K broadcast in the second channel search and executes a channel search for the other 4K broadcast (S6050b).

[0441] 32B(b), before actually starting a channel search for the other 4K broadcast, the control unit 50 performs demodulation settings for the other broadcast signal for the demodulation unit 20E, and performs decode settings for the other broadcast signal for the decoding unit 40 (S6051b). After completing these settings, the control unit 50 starts a channel search for the other 4K broadcast.

[0442] The control unit 50 determines whether or not the search of the other physical channels to be searched has been completed (S6052b). If the search of the other physical channels to be searched has not been completed (No in S6052b), the control unit 50 starts a channel search for a specific physical channel from among the other physical channels to be searched.

[0443] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6053b). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6054b).

[0444] If synchronization is not established (No in S6054b), the program information of the 4K broadcast cannot be acquired, and the control unit 50 sets the next other physical channel from among the search targets (S6070b).

[0445] If synchronization is established (Yes in S6054b), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6055b). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0446] Next, the control unit 50 determines whether or not there is an error in the layer of the other broadcast signal based on the demodulation information (S6056b). If the control unit 50 determines that there is an error in the layer of the other broadcast signal (Yes in S6056b), it does not acquire the program information of the other broadcast signal and sets the next other physical channel (S6070b). If the control unit 50 determines that there is no error in the layer of the other broadcast signal (No in S6056b), it acquires the program information of the other broadcast signal from the decoding unit 40 (S6059b). After acquiring the other program information, the control unit 50 sets the next other physical channel from among the search targets (S6070b).

[0447] After step S6070b, the control unit 50 determines whether or not the search of the other physical channel to be searched has been completed (S6052b).

[0448] If the control unit 50 has not yet completed searching all of the other physical channels to be searched (No in S6052b), it executes steps S6053b to S6070b again.If the control unit 50 has completed searching all of the other physical channels to be searched (Yes in S6052b), it ends the channel search for the other 4K broadcast.

[0449] In the channel search method of the sixth embodiment, the physical channels to be searched in the second channel search are determined based on information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming long when performing channel searches corresponding to both 2K broadcasting and 4K broadcasting.

[0450] In the above, an example has been described in which a channel search for one 4K broadcast is performed after a channel search for the other 4K broadcast, but this is not limited to this. It is also possible to perform a channel search for one 4K broadcast after a channel search for the other 4K broadcast.

[0451] [6-3. Variation 1 of the Sixth Embodiment] A channel search method according to the first modification of the sixth embodiment will be described.

[0452] In this variant example 1, among the broadcast signals of 4K broadcasting, the broadcast signal transmitted using the three-layer method or the LDM method may be referred to as one broadcast signal, and the broadcast signal transmitted using the new broadcast method may be referred to as the other broadcast signal.

[0453] In the first modification, the first error correction processing unit 31 and the second error correction processing unit 32 also perform different error correction processing. The first error correction processing unit 31 and the second error correction processing unit 32b also perform different error correction processing. The second error correction processing unit 32 and the second error correction processing unit 32b may perform the same error correction processing.

[0454] Fig. 33A is a flowchart showing a part of a channel search method according to Modification 1 of Embodiment 6. Fig. 33B is a flowchart showing another part of a channel search method according to Modification 1 of Embodiment 6.

[0455] 33A, the channel search method according to the first modification of the sixth embodiment includes step S6100 of performing a channel search for another broadcast signal of the 4K broadcasts, step S6110 of performing a first channel search that is a search for a first broadcast signal that is a 2K broadcast, and step S6150 of performing a second channel search that is a search for one broadcast signal of the 4K broadcasts after step S6110. The multiple physical channels include one physical channel that is the search target of the channel search for one broadcast signal and another physical channel that is the search target of the channel search for the other broadcast signal.

[0456] This channel search method also includes performing a first channel search for 2K broadcasting (first broadcast signal) on multiple physical channels, determining physical channels to be searched in a second channel search for one of the broadcast signals during the first channel search, and performing the second channel search on the physical channels that have been searched in the second channel search. Note that this channel search method also performs a channel search for the other broadcast signal before performing the first channel search.

[0457] Hereinafter, the detailed flow of step S6100 will be described in FIG. 33A, the detailed flow of step S6110 will be described in FIG. 33B(a), and the detailed flow of step S6150 will be described in FIG. 33B(b).

[0458] 33A(b), before actually starting a channel search for the other 4K broadcast, the control unit 50 performs demodulation settings for the other broadcast signal on the demodulation unit 20E and performs decode settings for the other broadcast signal on the decoding unit 40 (S6101). After completing these settings, the control unit 50 starts a channel search for the other broadcast signal.

[0459] First, the control unit 50 determines whether or not the search for all physical channels has been completed (S6102). If the search for all physical channels has not been completed (No in S6102), the control unit 50 starts a channel search for a specific physical channel from among the multiple physical channels.

[0460] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6103). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6104).

[0461] If synchronization has not been established (No in S6104), the control unit 50 determines this physical channel as the search target for the first channel search for 2K broadcasting. The control unit 50 registers this physical channel in the storage unit 60 (S6108) and sets the next physical channel for searching the other broadcast signal (S6109).

[0462] If synchronization is established (Yes in S6104), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6105). The demodulation information and control information are acquired from the other broadcast signal with which synchronization is established during the first channel search.

[0463] Next, the control unit 50 determines whether or not there is an error in the layer of the other broadcast signal based on the demodulation information (S6106). If the control unit 50 determines that there is an error in the layer of the other broadcast signal (Yes in S6106), it does not acquire the program information of the other broadcast signal and sets the next physical channel (S6109). If the control unit 50 determines that there is no error in the layer of the other broadcast signal (No in S6106), it acquires the program information of the other broadcast signal from the decoding unit 40 (S6107). After acquiring the program information of the other broadcast signal, the control unit 50 sets the next physical channel for searching the other broadcast signal (S6109).

[0464] After step S6109, the control unit 50 determines whether or not the search for all physical channels of the other broadcast signal has been completed (S6102). If the search for all physical channels has not been completed (No in S6102), the control unit 50 executes steps S6102 to S6109 and searches for the next physical channel. If the search for all physical channels of the other broadcast signal has been completed (Yes in S6102), the control unit 50 proceeds to step S6110 and executes a channel search for 2K broadcasts.

[0465] 33B(a), before actually starting a first channel search for 2K broadcasts, the control unit 50 performs 2K broadcast demodulation settings on the demodulation unit 20E and performs 2K broadcast decoding settings on the decoding unit 40 (S6111). After completing these settings, the control unit 50 starts a 2K broadcast channel search.

[0466] First, the control unit 50 determines whether or not searching of all physical channels to be searched has been completed (S6112). If searching of all physical channels to be searched has not been completed (No in S6112), the control unit 50 starts a channel search for a specific physical channel from among the physical channels to be searched.

[0467] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6113). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6114).

[0468] If synchronization has not been established (No in S6114), the next physical channel is set from among the search targets (S6130).

[0469] If synchronization is established (Yes in S6114), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6115). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcast with which synchronization is established during the channel search.

[0470] The control unit 50 determines, based on the control information, whether or not the physical channel with which synchronization has been established includes a 4K broadcast (S6116). If this physical channel includes a 4K broadcast (Yes in S6116), the control unit 50 sets this physical channel as one of the physical channels and determines this one physical channel as the search target for the channel search for one of the 4K broadcasts. The control unit 50 registers the one physical channel in the storage unit 60 (S6117) and proceeds to the next step, S6118. Note that if the physical channel with which synchronization has been established does not include a 4K broadcast (No in S6116), the one physical channel is not registered, and the process proceeds to the next step, S6118.

[0471] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S6118). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S6118), it does not acquire the 2K broadcast program information and sets the next physical channel (S6130). If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S6118), it acquires the 2K broadcast program information from the decoding unit 40 (S6119). After acquiring the 2K broadcast program information, the control unit 50 sets the next physical channel from the search targets (S6130).

[0472] After step S6130, the control unit 50 determines whether or not searching of all physical channels to be searched is complete (S6112). If searching of all physical channels to be searched is not complete (No in S6112), the control unit 50 executes steps S6113 to S6130 and searches for the next physical channel. If searching of all physical channels to be searched is complete (Yes in S6112), the control unit 50 proceeds to step S6150 and executes a channel search for one of the 4K broadcasts.

[0473] 33B(b), before actually starting a channel search for one 4K broadcast, the control unit 50 performs demodulation settings for one broadcast signal on the demodulation unit 20E, and performs decode settings for one broadcast signal on the decoding unit 40 (S6151). After completing these settings, the control unit 50 starts a channel search for one 4K broadcast.

[0474] The control unit 50 determines whether or not the search of one of the physical channels to be searched has been completed (S6152). If the search of one of the physical channels to be searched has not been completed (No in S6152), the control unit 50 starts a channel search for a specific physical channel from among the one of the physical channels to be searched.

[0475] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6153). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6154).

[0476] If synchronization is not established (No in S6154), the program information of one of the broadcast signals cannot be acquired, and therefore the control unit 50 sets the next physical channel from among the search targets (S6170).

[0477] If synchronization is established (Yes in S6154), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6155). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0478] Next, the control unit 50 determines whether or not there is an error in the layer of one of the broadcast signals based on the demodulation information (S6156). If the control unit 50 determines that there is an error in the layer of one of the broadcast signals (Yes in S6156), it does not acquire the program information of one of the broadcast signals and sets the next physical channel (S6170). If the control unit 50 determines that there is no error in the layer of one of the broadcast signals (No in S6156), it acquires the program information of one of the broadcast signals from the decoding unit 40 (S6159). After acquiring the program information of one of the broadcast signals, the control unit 50 sets the next physical channel from among the search targets (S6170).

[0479] After step S6170, the control unit 50 determines whether or not the search of one of the physical channels to be searched has been completed (S6152).

[0480] If the control unit 50 has not yet completed searching one of the physical channels to be searched (No in S6152), it executes steps S6153 to S6170 again. If the control unit 50 has completed searching one of the physical channels to be searched (Yes in S6152), it ends the channel search for one of the 4K broadcasts.

[0481] In the channel search method of the first modification of the sixth embodiment, the physical channels to be searched in the second channel search are determined based on information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming too long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts.

[0482] [6-4. Modification 2 of Embodiment 6] A channel search method according to the second modification of the sixth embodiment will be described.

[0483] In this variant example 2, among the broadcast signals of 4K broadcasting, the broadcast signal transmitted using the three-layer method or the LDM method may be referred to as one broadcast signal, and the broadcast signal transmitted using the new broadcast method may be referred to as the other broadcast signal.

[0484] In the second modification, the first error correction processing unit 31 and the second error correction processing unit 32 also perform different error correction processing. The first error correction processing unit 31 and the second error correction processing unit 32b also perform different error correction processing. The second error correction processing unit 32 and the second error correction processing unit 32b may perform the same error correction processing.

[0485] Fig. 34A is a flowchart showing a part of a channel search method according to Modification 2 of Embodiment 6. Fig. 34B is a flowchart showing another part of a channel search method according to Modification 2 of Embodiment 6.

[0486] 34A, the channel search method according to the second modification of the sixth embodiment includes step S6210 of performing a first channel search for a first broadcast signal, and step S6250b of performing a second channel search for a second broadcast signal after step S6210. The multiple physical channels include one physical channel that is the search target of the channel search for one broadcast signal, and another physical channel that is the search target of the channel search for the other broadcast signal.

[0487] This channel search method also includes determining, during a first channel search, a physical channel to be searched in a channel search of another broadcast signal (second broadcast signal) for a plurality of physical channels, and performing a channel search of the other broadcast signal for the physical channel that has become the search target of the channel search of the other broadcast signal. Note that this channel search method also performs a channel search for one of the 4K broadcast signals in the first channel search.

[0488] Hereinafter, the detailed flow of step S6210 will be described with reference to FIG. 34A, and the detailed flow of step S6250b will be described with reference to FIG. 34B.

[0489] 34A(b), the control unit 50 determines whether or not searching for all physical channels of 2K broadcasting is complete (S6211). If searching for all physical channels is not complete (No in S6211), the control unit 50 starts a channel search for a specific physical channel from among multiple physical channels.

[0490] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6212). The control unit 50 then sets the demodulation unit 20E to demodulate for 2K broadcasting, and sets the decoding unit 40 to decode for 2K broadcasting (S6213). The control unit 50 then determines whether synchronization with the frequency of the predetermined physical channel has been established in the tuner unit 10 (S6214).

[0491] If synchronization has not been established (No in S6214), the control unit 50 sets this physical channel as the other physical channel and determines this other physical channel as the search target for the channel search for the other 4K broadcast in the second channel search. The control unit 50 registers the other physical channel in the storage unit 60 (S6222) and sets the next physical channel for searching for 2K broadcast (S6230).

[0492] If synchronization is established (Yes in S6214), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6215). The demodulation information and control information are acquired from the broadcast signal of the 2K broadcast with which synchronization is established during the first channel search.

[0493] Next, the control unit 50 determines whether or not there is an error in the 2K broadcast layer based on the demodulation information (S6216). If the control unit 50 determines that there is an error in the 2K broadcast layer (Yes in S6216), it does not acquire the 2K broadcast program information and proceeds to the next step S6218. If the control unit 50 determines that there is no error in the 2K broadcast layer (No in S6216), it acquires the 2K broadcast program information from the decoding unit 40 (S6217) and proceeds to the next step S6218.

[0494] In step S6218, the control unit 50 determines whether or not this physical channel includes a 4K broadcast (S6218).

[0495] If the physical channel does not include 4K broadcasting (No in S6218), the control unit 50 does not determine the search target for the second channel search, and sets the next physical channel for searching for 2K broadcasting (S6230).If the physical channel includes 4K broadcasting (Yes in S6218), the control unit 50 sets this physical channel as the search target for the next channel search, and proceeds to the next step, S6254.

[0496] In step S6254, the control unit 50 sets the demodulation unit 20 to demodulate one broadcast signal, and sets the decoding unit 40 to decode one broadcast signal (S6254). Next, the control unit 50 acquires demodulation information and control information related to one broadcast signal from the demodulation unit 20 (S6255). The demodulation information and control information are acquired from the 2K broadcast signal with which synchronization was established during the first channel search.

[0497] Next, the control unit 50 determines whether or not there is an error in the layer of one of the broadcast signals based on the demodulation information (S6256). If the control unit 50 determines that there is an error in the layer of one of the broadcast signals (Yes in S6256), it does not acquire the program information of one of the broadcast signals and sets the next physical channel (S6230). If the control unit 50 determines that there is no error in the layer of one of the broadcast signals (No in S6256), it acquires the program information of one of the broadcast signals from the decoding unit 40 (S6259). Note that, although an example has been shown above in which the decoding setting for one of the broadcast signals in step S6254 is performed between steps S6218 and S6255, the present invention is not limited to this, and the decoding setting for one of the broadcast signals may be performed between steps S6255 and S6259.

[0498] When the acquisition of the program information of one broadcast signal is completed, the control unit 50 sets the next physical channel (S6230).

[0499] After step S6230, the control unit 50 determines whether or not the search for all of the physical channels has been completed (S6211).

[0500] If the control unit 50 has not finished searching all of the physical channels (No in S6211), it executes steps S6212 to S6259 again. On the other hand, if the control unit 50 has finished searching all of the physical channels (Yes in S6211), it executes a channel search for the other 4K broadcast (S6250b).

[0501] 34B, before actually starting a channel search for the other 4K broadcast, the control unit 50 performs demodulation settings for the other broadcast signal for the demodulation unit 20E, and performs decode settings for the other broadcast signal for the decoding unit 40 (S6251b). After completing these settings, the control unit 50 starts a channel search for the other 4K broadcast.

[0502] The control unit 50 determines whether or not the search of the other physical channels to be searched has been completed (S6252b). If the search of the other physical channels to be searched has not been completed (No in S6252b), the control unit 50 starts a channel search for a specific physical channel from among the other physical channels to be searched.

[0503] Next, the control unit 50 outputs a channel selection instruction signal to the tuner unit 10 to select a predetermined physical channel (S6253b). Then, the control unit 50 determines whether or not synchronization has been established with the frequency of the predetermined physical channel in the tuner unit 10 (S6254b).

[0504] If synchronization is not established (No in S6254b), the program information of the 4K broadcast cannot be acquired, and therefore the control unit 50 sets the next other physical channel from among the search targets (S6270b).

[0505] If synchronization is established (Yes in S6254b), the control unit 50 acquires demodulation information and control information from the demodulation unit 20E (S6255b). The demodulation information includes the above-mentioned synchronization information, C / N information, error information, etc.

[0506] Next, the control unit 50 determines whether or not there is an error in the layer of the other broadcast signal based on the demodulation information (S6256b). If the control unit 50 determines that there is an error in the layer of the other broadcast signal (Yes in S6256b), it does not acquire the program information of the other broadcast signal and sets the next other physical channel (S6270b). If the control unit 50 determines that there is no error in the layer of the other broadcast signal (No in S6256b), it acquires the program information of the other broadcast signal from the decoding unit 40 (S6259b). After acquiring the program information of the other broadcast signal, the control unit 50 sets the next other physical channel from the search targets (S6270b).

[0507] After step S6270b, the control unit 50 determines whether or not the search of the other physical channel to be searched has been completed (S6252b).

[0508] If the control unit 50 has not yet completed searching all of the other physical channels to be searched (No in S6252b), it executes steps S6253b to S6270b again. If the control unit 50 has completed searching all of the other physical channels to be searched (Yes in S6252b), it ends the second channel search.

[0509] In the channel search method of the second modification of the sixth embodiment, the physical channels to be searched in the second channel search are determined based on information acquired during the first channel search. This reduces the number of physical channels to be searched in the second channel search. This prevents the search time from becoming too long when performing channel searches corresponding to both 2K broadcasts and 4K broadcasts.

[0510] (summary) A channel search method according to the present disclosure is a channel search method for searching multiple physical channels of OFDM digital broadcasting. When a physical channel can contain both a first broadcast signal and a second broadcast signal, each of which has a different error correction processing method, or can contain either one of the first and second broadcast signals, the channel search method includes: performing a first channel search for the first broadcast signal on the physical channel; determining, during the first channel search, a physical channel to be searched in a second channel search for the second broadcast signal; and performing the second channel search on the physical channel that has been searched in the second channel search (see Embodiments 1, 2, 3, 4, 5, and 6).

[0511] In addition, the first broadcast signal includes control information indicating whether the physical channel includes the second broadcast signal, and the physical channel to be searched in the second channel search may be determined based on the control information obtained during the first channel search (see embodiment 1).

[0512] Alternatively, the control information may be acquired from the first broadcast signal with which synchronization is established during the first channel search (see the first embodiment).

[0513] Alternatively, the first broadcast signal may be transmitted in accordance with the ISDB-T standard, and the control information may be included in TMCC information or AC information of the first broadcast signal.

[0514] In addition, when a physical channel can include both a first broadcast signal and a second broadcast signal, an error determination of the first broadcast signal may be performed during the first channel search by performing a first error correction process corresponding to the first broadcast signal, and the physical channel to be searched in the second channel search may be determined based on the control information and information related to the error determination (see embodiment 1).

[0515] In addition, when a physical channel can include both a first broadcast signal and a second broadcast signal, an error determination may be made on the second broadcast signal by performing a second error correction process corresponding to the second broadcast signal during the first channel search, and the physical channel to be searched in the second channel search may be determined based on the control information and information related to the error determination (see embodiment 1).

[0516] Furthermore, when a physical channel can include both a first broadcast signal and a second broadcast signal, an error determination may be made on the first broadcast signal by performing a first error correction process corresponding to the first broadcast signal during the first channel search, and the physical channel determined to be error-free in the error determination may be the physical channel to be searched in the second channel search (see embodiment 1).

[0517] Furthermore, if a physical channel can include both a first broadcast signal and a second broadcast signal, the physical channel with which synchronization is established during the first channel search may be the physical channel to be searched in the second channel search (see embodiment 1).

[0518] In addition, when a physical channel can include either a first broadcast signal or a second broadcast signal, a physical channel with which synchronization was not established during the first channel search may be the physical channel to be searched in the second channel search (see embodiment 2).

[0519] In addition, when a physical channel can include either a first broadcast signal or a second broadcast signal, a physical channel on which synchronization was not established during the first channel search and whose in-band power value is equal to or greater than a predetermined threshold may be selected as the physical channel to be searched in the second channel search (see embodiment 3).

[0520] Furthermore, the second broadcast signal is either one of the first broadcast signal and another broadcast signal different from the first broadcast signal. The first broadcast signal and the first broadcast signal can exist as valid signals on the same physical channel, but the first broadcast signal and the other broadcast signal cannot exist as valid signals on the same physical channel. The physical channels targeted for the second channel search include the one physical channel and another physical channel different from the first physical channel, where the one physical channel is a physical channel of the first broadcast signal with which synchronization was established during the first channel search and which is indicated to include the second broadcast signal, and the other physical channel is a physical channel with which synchronization was not established during the first channel search. In these cases, the second channel search may include a channel search for one physical channel related to the one broadcast signal and a channel search for the other physical channel related to the other broadcast signal (see embodiment 6).

[0521] The channel search method of the present disclosure is a channel search method for searching a plurality of physical channels of OFDM digital broadcasting. When a physical channel can include both a first broadcast signal and a second broadcast signal that have different error correction processing methods, the channel search method includes: acquiring program information of the first broadcast signal when synchronization with the first broadcast signal is established during a search of a predetermined physical channel among the plurality of physical channels; and acquiring program information of the second broadcast signal when information indicating that the second broadcast signal is included in the predetermined physical channel is present (see Embodiment 4).

[0522] Furthermore, the program information of the first broadcast signal may be information determined to be error-free in the first broadcast signal when synchronization of the first broadcast signal is established, and the program information of the second broadcast signal may be information determined to be error-free in the second broadcast signal when there is information indicating that the second broadcast signal is included (see embodiment 4).

[0523] A channel search method of the present disclosure is a channel search method for searching a plurality of physical channels of OFDM digital broadcasting. When a physical channel can include either a first broadcast signal or a second broadcast signal having different error correction processing methods, the channel search method includes: acquiring program information of a first broadcast signal when synchronization with the first broadcast signal is established during a search of a predetermined physical channel among the plurality of physical channels; and acquiring program information of a second broadcast signal when synchronization with the first broadcast signal is not established during a search of the predetermined physical channel among the plurality of physical channels but synchronization with the second broadcast signal is established (see embodiment 5).

[0524] Furthermore, the program information of the first broadcast signal may be information that is determined to be error-free in the first broadcast signal when synchronization of the first broadcast signal is established, and the program information of the second broadcast signal may be information that is determined to be error-free in the second broadcast signal when synchronization of the first broadcast signal is not established and synchronization of the second broadcast signal is established (see embodiment 5).

[0525] In addition, the channel search method may further include performing decode settings for the first broadcast signal before acquiring program information for the first broadcast signal, and performing decode settings for the second broadcast signal before acquiring program information for the second broadcast signal (see embodiment 4).

[0526] Receiving devices 1 to 1E of the present disclosure are receiving devices that receive OFDM digital broadcasts. Each of the receiving devices 1 to 1E includes an AD conversion unit 21 that performs analog-to-digital conversion on an IF signal or a baseband signal input to the receiving device 1, a carrier synchronization unit 24 that performs synchronization processing based on the signal output from the AD conversion unit 21, an equalization unit 25 that performs equalization processing on the signal output from the carrier synchronization unit 24, a deinterleaving unit 28 that deinterleaves the signal output from the equalization unit 25, a first error correction processing unit 31 that performs first error correction processing on the signal output from the deinterleaving unit 28, and a second error correction processing unit 32 that performs second error correction processing, where the first error correction processing and the second error correction processing are different (see Embodiments 1, 2, 3, 4, 5, and 6).

[0527] In addition, the first error correction processing unit 31 may output a TS signal by performing Viterbi decoding or RS decoding on the signal output from the deinterleaving unit 28, and the second error correction processing unit may output a TS signal or a TLV signal by performing LDPC decoding or BCH decoding on the signal output from the deinterleaving unit 28.

[0528] Furthermore, the first error correction processing unit 31 and the second error correction processing unit 32 may each operate on a signal output from the equalization unit 25 based on the same IF signal or baseband signal.

[0529] The receiving device 1 further includes a storage unit 60 that stores a physical channel on which a desired digital broadcast signal is present among a plurality of physical channels of digital broadcast. Whether or not the desired digital broadcast signal is present on the physical channel may be determined based on at least one of the synchronization information output from the carrier synchronization unit 24, the control information output from the carrier synchronization unit 24, the error information output from the first error correction processing unit 31, and the error information output from the second error correction processing unit 32.

[0530] Furthermore, the second error correction processing unit 32 may perform the second error correction processing only on the physical channel on which the desired digital broadcast signal stored in the storage unit 60 exists.

[0531] The receiving device 1 further includes a decoding unit 40 that performs a decoding process on the signal output from the first error correction processing unit or the second error correction processing unit. The decoding unit 40 outputs program information related to the physical channel determined to be error-free by the first error correction processing unit 31 and program information related to the physical channel determined to be error-free by the second error correction processing unit 32 to the storage unit 60. The storage unit 60 may store the program information output from the decoding unit 40 in association with the physical channel on which the desired digital broadcast signal is present.

[0532] (Other embodiments) While the receiving device according to the aspects of the present disclosure has been described above based on embodiments, the present disclosure is not limited to these embodiments. For example, the present disclosure may be embodied in another embodiment realized by any combination of the components described in this specification or by excluding some of the components. Furthermore, the present disclosure also includes variations obtained by applying various modifications to the above embodiments that would occur to those skilled in the art without departing from the spirit of the present disclosure, i.e., the meaning of the wording set forth in the claims.

[0533] In the above embodiment, an example has been shown in which one of a plurality of digital broadcasts using different error correction processing methods is a 2K broadcast and the other is a 4K digital broadcast with a higher image quality than 2K, but this is not limiting. For example, the other digital broadcast may be an 8K digital broadcast with a higher image quality than 4K, or a digital broadcast with a lower image quality than 2K.

[0534] In the above embodiment, the presence or absence of 4K broadcasting is indicated by bit B of the TMCC information. 110 Although an example using bit B 110 instead of bit B20 or bit B 21 The signal may be indicated by using the reserve of the system identification signal, or by using other reserve areas or values ​​of the TMCC signal. Also, instead of the TMCC signal, a part of the AC signal, i.e., a part of the ISDB-T signal, may be used. In this case, the presence or absence of 4K broadcasting can be determined by decoding the signal.

[0535] In the above embodiment, the method shown in Non-Patent Document 1 or Non-Patent Document 2 has been described as a method for transmitting both 2K and 4K broadcasts, but this is not limiting. For example, a method may be used in which 4K broadcasts coexist on the same physical channel as existing 2K broadcasts, and the presence or absence of 4K broadcasts can be determined in the demodulation process of the ISDB-T system. The output of the 4K broadcast from the second error correction processor 32 is a TS signal or a TLV signal, but this is not limiting, and the content packet format may be another format.

[0536] For example, the configuration for demodulating 2K broadcasts and 4K broadcasts is not limited to the above embodiment. In Fig. 3, one deinterleave unit 28 is provided on the input sides of the first error correction processing unit 31 and the second error correction processing unit 32. However, this is not a limitation. A first deinterleave unit may be provided on the input side of the first error correction processing unit 31, and a second deinterleave unit may be provided on the input side of the second error correction processing unit 32. In Fig. 4, one deinterleave unit 28 is also provided. However, this is not a limitation. A first deinterleave unit may be provided on the input side of the first error correction processing unit 31, a second deinterleave unit may be provided on the input side of the second error correction processing unit 32, and a separator 29 may be provided on the input side of the second deinterleave unit.

[0537] In the error determination in the above-mentioned first to sixth embodiments, the presence or absence of an error in a 2K broadcast or 4K broadcast layer is determined as an example, but the present invention is not limited to this. For example, instead of determining the presence or absence of an error, the determination may be made based on a predetermined quality (C / N estimated value) or the like. Furthermore, determining the presence or absence of an error is not an essential determination item in the channel search method.

[0538] In the above-described third embodiment, the flow has been described in which the process proceeds to setting the next physical channel if the in-band power value is less than the threshold, but the in-band power value may also be applied to each of the flows in the first, second, fourth, fifth, and sixth embodiments. For example, in the first, second, fourth, fifth, and sixth embodiments, the process may proceed to setting the next physical channel if the in-band power value is less than the threshold after channel selection.

[0539] In addition, although the output selection unit is provided in the demodulation unit in the first to sixth embodiments, the output selection unit does not have to be provided in the demodulation unit. In this case, the signal from each error correction processing unit may be output to the decoding unit, and the decoding unit may select the signal.

[0540] In the above embodiment, the 2K broadcasting was described as being in the ISDB-T format, but this is not limited to this. The 2K broadcasting may be in a different format (e.g., DVB-T) and the 4K broadcasting may be superimposed on the same physical channel as this different format.

[0541] In the above-described fifth embodiment, an example in which 2K broadcasts and 4K broadcasts are searched for in sequence in one routine has been described, but this is not limiting. For example, one routine may simultaneously search for 2K broadcasts and 4K broadcasts, and acquire demodulation information, control information, and program information for the broadcast that is synchronized. If synchronization is not established with either broadcast, the next physical channel may be searched.

[0542] Furthermore, although the ISDB-T demodulation unit and the advanced standard demodulation unit are configured separately, they may be configured to share at least some of the calculations and memory.

[0543] The following aspects may also be included within the scope of one or more aspects of the present disclosure.

[0544] (1) Some of the components constituting the above-mentioned receiving device may be a computer system consisting of a microprocessor, ROM, RAM, hard disk unit, display unit, keyboard, mouse, etc. A computer program is stored in the RAM or hard disk unit. The microprocessor operates in accordance with the computer program to achieve its functions. Here, the computer program is composed of a combination of multiple instruction codes that indicate commands to a computer to achieve a predetermined function.

[0545] (2) Some of the components constituting the above-mentioned receiving device may be configured as a single system LSI (Large Scale Integration). The system LSI is an ultra-multifunctional LSI manufactured by integrating multiple components on a single chip, and specifically, is a computer system configured including a microprocessor, ROM, RAM, etc. A computer program is stored in the RAM. The system LSI achieves its functions when the microprocessor operates in accordance with the computer program.

[0546] (3) Some of the components constituting the above-mentioned receiving device may be composed of an IC card or a standalone module that can be attached to each device. The IC card or the module is a computer system composed of a microprocessor, ROM, RAM, etc. The IC card or the module may include the above-mentioned ultra-multifunctional LSI. The IC card or the module achieves its functions when the microprocessor operates according to a computer program. The IC card or the module may be tamper-resistant.

[0547] (4) Furthermore, some of the components constituting the above-mentioned receiving device may be the computer program or the digital signal recorded on a computer-readable recording medium, such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray (registered trademark) Disc), semiconductor memory, etc. Alternatively, they may be the digital signal recorded on such a recording medium.

[0548] In addition, some of the components constituting the above-mentioned receiving device may transmit the computer program or the digital signal via a telecommunications line, a wireless or wired communication line, a network such as the Internet, data broadcasting, etc.

[0549] (5) The present disclosure may be embodied as the methods described above, a computer program for implementing these methods on a computer, or a digital signal comprising the computer program.

[0550] (6) The present disclosure may also be a computer system having a microprocessor and a memory, the memory storing the computer program, and the microprocessor operating in accordance with the computer program.

[0551] (7) The program or the digital signal may also be implemented by another independent computer system by recording it on the recording medium and transferring it, or by transferring the program or the digital signal via the network, etc.

[0552] (8) The above-described embodiments and modifications may be combined with each other. [Industrial Applicability]

[0553] The channel search method of the present disclosure can be used in a receiving device that receives digital broadcasts. [Explanation of symbols]

[0554] 1, 1A, 1B, 1C, 1D, 1E receiving device 2 antennas 10, 10B Tuner section 20, 20A, 20B, 20E Demodulation section 20Aa, 20Ba, 20Ea First demodulation section 20Ab, 20Bb, 20Eb Second demodulation section 21 AD conversion section 22, 22a, 22b Time axis processing section 23, 23a, 23b FFT section 24, 24a, 24b Carrier synchronization section 25, 25a, 25b equalization section 26, 26a, 26b TMCC decoding unit 27 4K broadcast control information decoding unit 28, 28a, 28b Deinterleave section 29 Separation section 31, 31a First error correction processing unit 32, 32b Second error correction processing unit 33 Output selection section 40 Decoding section 50 control section 60 Storage section 70 Display section

Claims

1. A channel search method for searching a plurality of physical channels of digital broadcasting using an OFDM (Orthogonal Frequency Division Multiplexing) system, comprising: When the physical channel can include both a first broadcast signal and a second broadcast signal having different error correction processing methods, or can include either one of the first broadcast signal and the second broadcast signal, performing a first channel search for the first broadcast signal on the physical channel; determining, during the first channel search, the physical channel to be searched in a second channel search for the second broadcast signal; performing the second channel search on the physical channel that is the search target of the second channel search; A channel search method including:

2. After performing the first channel search on the plurality of physical channels, the second channel search is performed on the physical channels that are search targets of the second channel search.

2. The channel search method according to claim 1.

3. the first broadcast signal includes control information indicating whether the second broadcast signal is included in the physical channel; The physical channel to be searched in the second channel search is determined based on the control information acquired during the first channel search.

3. The channel search method according to claim 2.

4. the control information is acquired from the first broadcast signal with which synchronization is established during the first channel search; 4. The channel search method according to claim 3.

5. the first broadcast signal is transmitted by an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) system, The control information is included in TMCC (Transmission Multiplexing Configuration Control) information or AC (Auxiliary Channel) information of the first broadcast signal.

5. The channel search method according to claim 3 or 4.

6. If the physical channel is capable of containing both the first broadcast signal and the second broadcast signal, During the first channel search, a first error correction process corresponding to the first broadcast signal is performed to determine an error in the first broadcast signal, and the physical channel to be searched in the second channel search is determined based on the control information and information related to the error determination. The channel search method according to any one of claims 3 to 5.

7. If the physical channel is capable of containing both the first broadcast signal and the second broadcast signal, During the first channel search, a second error correction process corresponding to the second broadcast signal is performed to determine an error in the second broadcast signal, and the physical channel to be searched in the second channel search is determined based on the control information and information related to the error determination. The channel search method according to any one of claims 3 to 5.

8. If the physical channel is capable of containing both the first broadcast signal and the second broadcast signal, During the first channel search, a first error correction process corresponding to the first broadcast signal is performed to determine whether there is an error in the first broadcast signal, and a physical channel determined to be error-free in the error determination is set as the physical channel to be searched in the second channel search.

3. The channel search method according to claim 2.

9. If the physical channel is capable of containing both the first broadcast signal and the second broadcast signal, a physical channel with which synchronization is established during the first channel search is set as the physical channel to be searched in the second channel search; 3. The channel search method according to claim 2.

10. When the physical channel is capable of including either the first broadcast signal or the second broadcast signal, a physical channel with which synchronization has not been established during the first channel search is set as the physical channel to be searched in the second channel search; 3. The channel search method according to claim 2.

11. When the physical channel is capable of including either the first broadcast signal or the second broadcast signal, a physical channel for which synchronization has not been established during the first channel search and for which the in-band power value of the physical channel is equal to or greater than a predetermined threshold is set as the physical channel to be searched in the second channel search; 3. The channel search method according to claim 2.

12. the second broadcast signal is either one of the first broadcast signal and another broadcast signal different from the first broadcast signal, the first broadcast signal and the other broadcast signal may exist as valid signals on the same physical channel; the first broadcast signal and the other broadcast signal cannot exist as valid signals on the same physical channel; the physical channels that are the targets of the second channel search include one physical channel and another physical channel that is different from the one physical channel; the one physical channel is a physical channel of the first broadcast signal with which synchronization is established during the first channel search, and is a physical channel indicated to include the second broadcast signal; the other physical channel is a physical channel with which synchronization was not established during the first channel search; In the second channel search, a channel search is performed on the one physical channel related to the one broadcast signal, and a channel search is performed on the other physical channel related to the other broadcast signal.

3. The channel search method according to claim 2.

13. After performing the first channel search on the physical channel, the second channel search is performed on the physical channel before performing the first channel search on another physical channel.

2. The channel search method according to claim 1.

14. When the physical channel can include both a first broadcast signal and a second broadcast signal which have different error correction processing methods, acquiring program information of the first broadcast signal when synchronization with the first broadcast signal is established during a search of a predetermined physical channel among the plurality of physical channels; acquiring program information of the second broadcast signal when there is information indicating that the second broadcast signal is included in the predetermined physical channel; 14. The channel search method of claim 13, comprising:

15. the program information of the first broadcast signal is information determined to be error-free when synchronization of the first broadcast signal is established; The program information of the second broadcast signal is information that is determined to be error-free when there is information indicating that the second broadcast signal is included. The channel search method according to claim 14.

16. When the physical channel can include either a first broadcast signal or a second broadcast signal having different error correction processing methods, acquiring program information of the first broadcast signal when synchronization with the first broadcast signal is established during a search of a predetermined physical channel among the plurality of physical channels; acquiring program information of the second broadcast signal when synchronization of the first broadcast signal is not established and synchronization of the second broadcast signal is established during a search of a predetermined physical channel among the plurality of physical channels; 14. The channel search method of claim 13, comprising:

17. the program information of the first broadcast signal is information determined to be error-free when synchronization of the first broadcast signal is established; The program information of the second broadcast signal is information determined to be error-free when synchronization of the first broadcast signal is not established and synchronization of the second broadcast signal is established. The channel search method according to claim 16.

18. moreover, performing a decoding setting for the first broadcast signal before acquiring program information of the first broadcast signal; performing a decoding setting for the second broadcast signal before acquiring program information of the second broadcast signal; The channel search method according to any one of claims 14 to 17, comprising:

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