Reception device, reception method, and program

Abstract

To provide a reception device capable of realizing time information, which is required for time synchronism at a reception side, in simple circuit configuration.SOLUTION: A reception device performs OFDM demodulation on a broadcast wave in an OFDM demodulation section, extracts an IP packet from a TLV packet in a TLV decode section, acquires NTP time information from the IP packet in an NTP time acquisition section, generates an FEC block cycle from a modulation parameter in an FEC block cycle generation section, generates a present time acquisition signal on an N-times FEC block cycle basis in an N-times count section, generates a present time in a time generation section, calculates a difference between an NTP time and the present time in a time comparison section, adjusts an operation frequency so as to reduce the difference in a clock oscillator, and performs decode processing of an MMTP / IP packet in a case where the IP packet is an MMTP / IP packet in an MMT decode section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a receiving device, a receiving method, and a program for achieving clock synchronization with a transmitting side in 4K8K satellite broadcasting. [Background technology]

[0002] Conventionally, in 4K8K satellite broadcasting, a packet in the Network Time Protocol (NTP) format for synchronizing the clocks of the sending side and the receiving side is inserted at the beginning of the slot at the beginning of the frame (Non-Patent Documents 1 and 2). In addition, when hierarchical modulation is performed, the packet is inserted at the beginning slot of a low hierarchy (Non-Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent No. 6290127 [Patent Document 2] Japanese Patent No. 6517905 [Non-patent literature]

[0004] [Non-Patent Document 1] ARIB STD-B44 [Non-Patent Document 2] ARIB STD-B39 [Non-Patent Document 3] Ministry of Internal Affairs and Communications: Call for Comments on the Draft Report of the Broadcasting System Committee - "Technical Conditions for Broadcasting Systems" - Ministry of Internal Affairs and Communications | Press Releases | Call for Comments on the Draft Report of the Broadcasting System Committee (https: / / www.soumu.go.jp) (Retrieved June 27, 2023) Summary of the Invention [Problem to be solved by the invention]

[0005] However, such a conventional clock synchronization method has the following problems.

[0006] The MMT (MPEG Media Transport) standard does not prescribe anything equivalent to a PCR (Program Clock Reference) packet, which is a type of TS packet that transmits time information, as the TS (Transport Stream) standard does. Therefore, 4K8K satellite broadcasting synchronizes the time of the broadcast transmission system with the time of the receiver by sending IP (Internet Protocol) packets in NTP format at frame intervals.

[0007] However, in the advanced terrestrial digital broadcasting system, it is very difficult to send NTP format IP packets at a timing that perfectly matches the period of the OFDM (Orthogonal Frequency Division Multiplexing) frame.

[0008] For example, to solve the above problem, it is possible to send NTP format IP packets at any timing, as in the case of TS PCR packets, but because the MMT·TLV (Type Length Value) packets before and after them are variable length, the circuit configuration for acquiring the current time required for time synchronization on the receiving side becomes complicated. Also, the delay in error correction processing changes depending on the number of recursive error corrections, causing jitter, making stable clock recovery difficult.

[0009] The problem to be solved by the present invention is to provide a receiving device, a receiving method, and a program that can realize, with a simple circuit configuration, the time information required for time synchronization on the receiving side. [Means for solving the problem]

[0010] The receiving device of the embodiment includes an OFDM demodulation unit, a TLV decoding unit, an NTP time acquisition unit, an FEC block cycle generation unit, an N-time count unit, a time generation unit, a current time acquisition unit, a time comparison unit, a clock oscillator, and an MMT decoding unit. The OFDM demodulation unit performs OFDM demodulation of a broadcast wave to output a TLV packet for each layer, recover a clock during modulation, and extract a modulation parameter. The TLV decoding unit extracts an IP packet from the TLV packet. The NTP time acquisition unit acquires NTP time information from an NTP-formatted IP packet of an appropriate layer. The FEC block cycle generation unit operates with the clock recovered by the OFDM demodulation unit, and generates an FEC (Forward Error Correction) block cycle from the modulation parameter. The N-time count unit generates a current time acquisition signal for every N FEC block cycles, which is an integer equal to or greater than 1, obtained from the modulation parameter. The time generation unit operates with an adjusted operating frequency, and generates a current time. The current time acquisition unit acquires the current time from the time generation unit when the current time acquisition signal is generated. The time comparison unit compares the NTP time information with the current time to obtain the difference between the NTP time and the current time. The clock oscillator adjusts the operating frequency so that the difference becomes small. The MMT decoding unit performs a decoding process for the MMTP / IP packet when the IP packet extracted by the TLV decoding unit is an MMTP / IP packet. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a receiving device to which the receiving method of the first embodiment is applied. [Diagram 2] FIG. 2 is a diagram showing the configuration of an FEC block traced based on Non-Patent Document 3. [Diagram 3] FIG. 3 is a table showing the configuration of an FEC block traced based on Non-Patent Document 3. [Figure 4] FIG. 4 is a table showing calculation conditions of the information rate traced based on Non-Patent Document 3. [Diagram 5]FIG. 5 is an information bit table traced based on Non-Patent Document 3. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a receiving device to which the receiving method of the second embodiment is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as the actual ones. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with respect to the previous drawings are given the same reference numerals, and detailed explanations and duplicated explanations are omitted as appropriate.

[0013] (First embodiment) Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a block diagram showing an example of the configuration of a receiving device to which the receiving method of the first embodiment is applied.

[0015] That is, the receiving device 10 of this embodiment includes an OFDM demodulation unit 11, a TLV decoding unit 12, an NTP time acquisition unit 13, an FEC block period generation unit 14, an N-time counting unit 15, a time generation unit 16, a current time acquisition unit 17, a time comparison unit 18, a clock oscillator 19, an MMT decoding unit 20, and a display unit (monitor) 21.

[0016] The OFDM demodulation unit 11 receives, for example, a broadcast wave a transmitted from a broadcast station, and performs OFDM demodulation to output a TLV packet b for each layer, recover a clock c used during modulation, and extract a modulation parameter d.

[0017] As described in Non-Patent Document 3, the modulation parameter d is composed of (A) the size of the FEC block, (B) the coding rate, (C) the carrier modulation method, and (D) the FFT (Fast Fourier Transform) size of the subframe section.

[0018] (A) The size of the FEC block is N shown in FIG. 2, which is based on the diagram disclosed in Non-Patent Document 3. LDPC It is.

[0019] (B) The coding rate is shown in FIG. 3, which is based on the diagram disclosed in Non-Patent Document 3.

[0020] (C) The carrier modulation method is shown in FIG. 3, which is based on the diagram disclosed in Non-Patent Document 3.

[0021] (D) The FFT size in the subframe section is shown in FIG. 4, which is based on the diagram disclosed in Non-Patent Document 3.

[0022] FIG. 5 is also based on the diagram disclosed in Non-Patent Document 3, but in the calculation of the information bit rate in FIG. LDPC = 61,920 (Normal code).

[0023] In the following, the above four modulation parameters are abbreviated as A, B, C, and D, and three specific examples ((1), (2), and (3)) will be used for explanation.

[0024] (1) When B is 2 / 16, C is QPSK, and D is 8K FFT, the main signal is 8,432 bits from Fig. 3(a), and the information rate is 1.19 Mbps from Fig. 5(a). Therefore, the period of the FEC block is 8,432 / (1.19*1000000)=0.007085714 seconds ≒ 7.09 milliseconds.

[0025] (2) If B is 7 / 16, C is 64QAM, and D is 16K FFT, the main signal is 30,032 bits from Fig. 3(a), and the information rate is 13.35Mbps from Fig. 5(b). Therefore, the period of the FEC block is 30,032 / (13.35*1000000)=0.002249588 seconds ≒ 2.25 milliseconds.

[0026] (3) If B is 14 / 16, C is 4096QAM, and D is 32K FFT, the main signal is 60,272 bits from Fig. 3(a), and the information rate is 54.92Mbps from Fig. 5(c). Therefore, the period of the FEC block is 60,272 / (54.92*1000000)=0.001097451≒1.10 milliseconds.

[0027] Returning to FIG.

[0028] The TLV decoding unit 12 extracts the IP packet e from the TLV packet b output by the OFDM demodulation unit 11 .

[0029] The NTP time acquisition unit 13 acquires NTP time information f from the NTP format IP packets e of an appropriate hierarchy among the IP packets e extracted by the TLV decoding unit 12 , and outputs the information to the time generation unit 16 .

[0030] The FEC block period generator 14 operates in accordance with the clock c recovered by the OFDM demodulator 11 , generates an FEC block period g from the modulation parameters d, and outputs it to the N-times count unit 15 .

[0031] The N-times counting unit 15 generates a current time acquisition signal h for every N-times FEC block period g, which is an integer equal to or greater than 1 and is obtained from the modulation parameter d, and outputs the signal h to the current time acquisition unit 17 .

[0032] In the three specific examples ((1), (2), and (3)) described regarding the modulation parameter d, the FEC block period ranges from 1.10 ms to 7.09 ms. Current terrestrial digital broadcasting uses TS, and the transmission cycle of PCR packets containing time information is approximately 100 ms. In addition, in the new 4K8K satellite broadcasting, NTP format packets are transmitted at the beginning of each frame, so the transmission cycle is approximately 33 ms.

[0033] For example, if one tries to use N to make the period of the FEC block approximately the same as the cycle of the new 4K8K satellite broadcasting, in the case of (1), 33 (milliseconds) / 7.09 (milliseconds) = 4.66, so the maximum value of N for which the period of the FEC block does not exceed 33 milliseconds is 4, and the value of N that is closest to 33 milliseconds is 5.

[0034] In the case of (2), 33 milliseconds / 2.26 (milliseconds)=14.67, so the maximum value of N for which the period of the FEC block does not exceed 33 milliseconds is 14, and the value of N that is closest to 33 milliseconds is 15.

[0035] In the case of (3), 33 milliseconds / 1.10 (milliseconds)=30.07, so the maximum value of N for which the period of the FEC block does not exceed 33 milliseconds is 30, and the value of N that is closest to 33 milliseconds is also 30.

[0036] That is, a rule for determining N is determined in advance between the sending side and the receiving side such that the period of N FEC blocks does not exceed 33 milliseconds or is closest to 33 milliseconds.

[0037] The N-times counting unit 15 acquires N from the modulation parameter d, generates a current time acquisition signal h for every N FEC block periods g, and outputs the generated current time acquisition signal h to the current time acquiring unit 17.

[0038] The time generating unit 16 operates at an operating frequency i adjusted by a clock oscillator 19, and generates a current time j.

[0039] The current time acquisition unit 17 acquires the current time j from the time generation unit 16 at the timing when the current time acquisition signal h is generated, and outputs it to the time comparison unit 18.

[0040] The time comparison unit 18 compares the NTP time information f from the NTP time acquisition unit 13 with the current time j from the current time acquisition unit 17 to find the difference k between the NTP time and the current time, and outputs the difference k to the clock oscillator 19.

[0041] The clock oscillator 19 adjusts the operating frequency i outputted to the time generating unit 16 so as to reduce the difference k.

[0042] The MMT decoding unit 20 performs a decoding process on the IP packet e when the IP packet e extracted by the TLV decoding unit 12 is an MMTP / IP packet.

[0043] In particular, the MMT decoding unit 20 performs a decoding process on at least one of video, audio, subtitles, and a transmission control signal.

[0044] The decoded IP packet e' is output to the display unit 21, and is displayed on the monitor of the display unit 21.

[0045] When the receiving device 10 starts operating, for example, the NTP time information f acquired by the NTP time acquisition unit 13 is loaded as the current time. The timing of loading can be (α) when the N-time count unit 15 generates a current time acquisition signal h, or (β) when the NTP time acquisition unit 13 acquires the NTP time information f from an NTP format IP packet.

[0046] In addition, the timing at which the time comparison unit 18 compares the NTP time information f with the current time j can be, for example, (a) when a current time acquisition signal h is generated, or (b) when the NTP time information f is acquired from an NTP format IP packet.

[0047] In the case of (a), the timing (α) is desirable for loading the current time at the start of operation. In the case of (b), the timing (β) is desirable for loading the current time at the start of operation.

[0048] Alternatively, in the case of (a), the initial time is loaded at the timing of (β), but the counter of the N-times counting unit is reset to 0 (zero) when the initial time is loaded.

[0049] Next, the operation of the receiving device 10 of this embodiment configured as above will be described.

[0050] In the receiving device 10, the OFDM demodulation unit 11 performs OFDM demodulation on the received broadcast wave a, and outputs a TLV packet b for each layer. At this time, the clock c used during modulation is recovered. In addition, a modulation parameter d is also extracted.

[0051] In the TLV decoding unit 12, the IP packet e contained in the TLV packet b is extracted.

[0052] In the NTP time acquisition unit 13, the NTP time information f is acquired from the NTP format IP packet e of the appropriate layer. For example, the NTP format IP packet e is extracted from a layer with high error correction capability, or the NTP format IP packet e is extracted from a layer containing a package that performs its own service even if the layer has low error correction capability. This is performed, for example, by referring to an identifier indicating which layer the NTP format IP packet e is contained in.

[0053] The FEC block period generator 14 operates in accordance with the clock c recovered by the OFDM demodulator 11, thereby generating an FEC block period g determined from the modulation parameters d.

[0054] In the N-times counting unit 15, N is calculated from the modulation parameter d, and a current time acquisition signal h is generated every N-times of the FEC block period g. Note that N may be extracted from a descriptor. Extracting N from a descriptor will be described in the second embodiment.

[0055] The current time acquiring unit 17 acquires the current time j of the time generating unit 16 at the timing of the current time acquisition signal h.

[0056] The time comparison unit 18 compares the NTP time information f with the current time j, and finds the difference k between the NTP time and the current time.

[0057] In the clock oscillator 19, the operating frequency i of the clock oscillator 19 is adjusted so that the difference k becomes smaller.

[0058] The time generating unit 16 operates at an operating frequency i of a clock oscillator 19 .

[0059] In the MMT decoding unit 20, a decoding process is performed when the output from the TLV decoding unit 12 is an MMTP / IP packet. The decoding process is performed on video, audio, subtitles, transmission control signals, and the like.

[0060] 1, the FEC block period generation unit 14 is illustrated as an independent block, but the FEC block period generation unit 14 may be implemented as being built into the OFDM demodulation unit 11. Also, the modulation parameter d may be implemented as being held in the OFDM demodulation unit 11.

[0061] In this way, the receiving device 10 of this embodiment acquires the time information required for time synchronization on the receiving side at regular intervals according to the modulation parameter d, and therefore can be realized with a simple circuit configuration.

[0062] Second embodiment A receiving device according to a second embodiment of the present invention will be described.

[0063] FIG. 6 is a block diagram showing an example of the configuration of a receiving device to which the receiving method of the second embodiment is applied.

[0064] 6, the same components as those in the first embodiment are denoted by the same reference numerals. In the following description, overlapping descriptions will be avoided and only differences will be described.

[0065] The receiving device 10A of the second embodiment is a modified example of the receiving device 10 of the first embodiment, and can be implemented when a packet with N added to a descriptor is output from the transmitting side, and the N-times counting unit 15 extracts the value of N from the descriptor included in the TLV packet b instead of obtaining it from the modulation parameter d.

[0066] In this way, by acquiring N from the descriptor, the receiving device 10A is able to grasp the value of N designated by the user on the transmitting side and perform demodulation every N times.

[0067] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0068] 10, 10A receiving device 11 OFDM demodulation section 12 TLV Decoder 13 NTP time acquisition section 14 FEC block period generator 15 N-times counting section 16 Time generator 17 Current time acquisition part 18 Time comparison section 19 Clock Oscillator 20 MMT Decoding Section 21 Display unit (monitor) a Broadcasting b TLV packet c Clock d Modulation parameters e, e' IP packets f NTP time information g FEC block period h Current time acquisition signal i Operating frequency j Current time k difference

Claims

1. an OFDM demodulation unit that demodulates the broadcast wave using Orthogonal Frequency Division Multiplexing (OFDM) to output a TLV (Type Length Value) packet for each layer, recover a clock used during modulation, and extract modulation parameters; A TLV decoding unit that extracts an IP (Internet Protocol) packet from the TLV packet; an NTP time acquisition unit for acquiring NTP time information from an IP packet in an NTP (Network Time Protocol) format of an appropriate layer; an FEC block period generator that operates with a clock reproduced by the OFDM demodulator and generates a FEC (Forward Error Correction) block period from the modulation parameters; an N-times counting unit that generates a current time acquisition signal for each N-times of the FEC block periods, where N is an integer equal to or greater than 1, obtained from the modulation parameters; a time generating unit that operates at the adjusted operating frequency and generates a current time; a current time acquisition unit that acquires the current time from the time generation unit at a timing when the current time acquisition signal is generated; a time comparison unit that compares the NTP time information with the current time to obtain a difference between the NTP time and the current time; a clock oscillator that adjusts the operating frequency so that the difference is small; an MMT decoding unit that performs a decoding process of the MMTP / IP packet when the IP packet extracted by the TLV decoding unit is an MMTP (MPEG Media Transport) / IP packet; A receiving device comprising:

2. The receiving device according to claim 1 , wherein the MMT decoding unit performs the decoding process on at least one of video, audio, subtitles, and a transmission control signal.

3. The modulation parameters are stored in the OFDM demodulation unit; The receiving device according to claim 1 , wherein the FEC block cycle generation unit is built into the OFDM demodulation unit.

4. The N is added as additional information to a descriptor included in the TLV packet, The receiving device according to claim 1 , wherein the N-times counting unit extracts the value of N from a descriptor included in the TLV packet instead of obtaining the value from the modulation parameters.

5. A receiving method implemented by a processor of a receiving device, comprising: The processor performs OFDM demodulation of the broadcast wave to output a TLV packet for each layer, recover a clock during modulation, and extract modulation parameters; The processor extracts an IP packet from the TLV packet; said processor obtaining NTP time information from an appropriate stratum of NTP formatted IP packets; said processor operating on said recovered clock generating an FEC block period from said modulation parameters; generating a current time acquisition signal for every N FEC block periods, N being an integer greater than or equal to 1, derived from the modulation parameters; said processor operating at an adjusted operating frequency and generating a current time; The processor acquires the current time at the timing when the current time acquisition signal is generated; said processor comparing said NTP time information with said current time to determine a difference between said NTP time and said current time; said processor adjusting said operating frequency so as to reduce said difference; a step of the processor performing a decoding process of the extracted IP packet when the IP packet is an MMTP / IP packet; A receiving method including:

6. 6. The receiving method according to claim 5, wherein said decoding step performs said decoding process on at least one of video, audio, subtitles, and a transmission control signal.

7. The N is added as additional information to a descriptor included in the TLV packet, The receiving method of claim 5 , wherein the generating step includes the step of extracting the value of N from a descriptor included in the TLV packet instead of obtaining the value from the modulation parameters.

8. A function to output TLV packets for each layer, recover the clock during modulation, and extract modulation parameters by OFDM demodulating the broadcast wave; Extracting an IP packet from the TLV packet; The ability to obtain NTP time information from NTP format IP packets at the appropriate hierarchical level; a function operating on said recovered clock and generating an FEC block period from said modulation parameters; a function of generating a current time acquisition signal for every N FEC block periods, where N is an integer equal to or greater than 1, obtained from the modulation parameters; The function of operating at a regulated operating frequency and generating the current time, A function of acquiring the current time at the timing when the current time acquisition signal is generated; a function of comparing the NTP time information with the current time to obtain a difference between the NTP time and the current time; a function of adjusting the operating frequency so that the difference is reduced; When the extracted IP packet is an MMTP / IP packet, a function of performing a decoding process of the MMTP / IP packet is provided. A program that makes things happen on a computer.

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