Signal switching device and signal switching method

Abstract

To provide a signal switching device and a signal switching method that can realize switching without shock of an image sound at the time of switching.SOLUTION: A signal switching device according to an embodiment separates a MPU and a packet of the MPT before and after switching from an IP data flow and a packet_id, obtains an MPU number of each MPU from an MPU time stamp descriptor, outputs an MMTP packet with the access unit count counter initialized to zero at the change point, obtains each MPU number and the first presentation time of the access unit included in each MPU from the MPU time stamp descriptor, obtains the MPU number of each MPU and the presentation time of each access unit of the MPU from the MPU extended time stamp descriptor, obtains the last presentation time of each access unit, and selects the last MMTP packet before switching, and the last MMTP packet after switching.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a signal switching device and a signal switching method used in broadcasting systems including terrestrial digital broadcasting, satellite broadcasting, CATV, IP retransmission, and the like. [Background technology]

[0002] In current digital broadcasting systems that use TS (Transport Stream) and MMT (MPEG Multimedia Transport), program switching is performed using unencoded baseband signals to prevent unintended images from being seen for a moment (glimpses) when switching programs (Non-Patent Document 1).

[0003] In order to prevent broadcast interruptions due to equipment failure, a redundant system is constructed with a working system and a backup system, and system switching is performed during regular equipment maintenance, resulting in seamless switching that does not cause image or sound shocks on the receiver. At the switching point, the encoder is controlled to start a new GOP at the switching point and to ensure that the transmission timing is continuous (satisfying the specified timing) when the last GOP of the system before the switch and the first GOP of the system after the switch are linked (Non-Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-125741 A [Patent Document 2] JP 2018-125742 A [Patent Document 3] JP 2018-157467 A [Patent Document 4] JP 2018-160787 A [Non-patent literature]

[0005] [Non-Patent Document 1] Toshiba Review, Vol. 59, No. 2 (2004), pp. 24-27, "Studio System Equipment for Digital Terrestrial Broadcasting, 2. Switcher Device" [Non-Patent Document 2] NEC Technical Journal, Vol. 57, No. 4 (2004), pp. 31-34, "Development of Multiplexing Equipment, Chapter 4. System Features" [Non-Patent Document 3] Toshiba Review, Vol. 59, No. 2 (2004), pp. 7-17, "Terrestrial Digital Broadcasting Master Transmission System, 6.2 SCS" Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventionally, program switching has had to be performed in baseband, and it has not been possible to realize program switching between a streamer that records material that has been encoded for broadcast in advance and a live encoder, or between streamers.

[0007] Furthermore, when switching from the working system to the spare system of the redundant system, it is necessary to control the GOP start position and the code amount for the encoder, and equipment support for this control is required.

[0008] The problem that the present invention aims to solve is to provide a signal switching device and a signal switching method that can realize switching without the need to perform it in baseband or without the need to control the GOP start position and code amount, and that can achieve switching without any shock to images and sounds at the time of switching, or with reduced shock. [Means for solving the problem]

[0009] The signal switching device of the embodiment is a signal switching device for switching from an IP data flow before switching to an IP data flow after switching, and includes an MMTP packet header analysis unit, an MMTP payload header analysis unit, an MPU time stamp descriptor analysis and rewriting unit, an MPU extended time stamp descriptor analysis and rewriting unit, and an MMTP packet selection unit. The MMTP packet header analysis unit refers to the IP data flow and packet_id sent from the upstream side, and separates packets of assets (MPU: Media Processing Unit) and packets of PA (Package Access) messages (MPT: MMT Package Table) from MMTP (MPEG Media Transport Protocol) before switching and after switching. The MMTP payload header analysis unit obtains the MPU number of each MPU from the MPU time stamp descriptor of each MPU included in the MPT separated by the MMTP packet header analysis unit, and initializes a counter of the number of access units to zero at the change point of each MPU number constituting an asset. The MPU timestamp descriptor parsing and rewriting unit obtains each MPU number separated by the MMTP packet header parsing unit and the first presentation time of the access unit included in each MPU from the MPU timestamp descriptor. The MPU extended timestamp descriptor parsing and rewriting unit obtains the MPU number of each MPU and the presentation time of each access unit of the MPU based on the first presentation time of the access unit from the MPU extended timestamp descriptor of each MPU, and further obtains the last presentation time of each access unit. The MMTP packet selection unit selects the last MMTP packet before the switch and the first MMTP packet after the switch based on the specified switch time, the presentation time of the last access unit in the last MPU before the switch from the MPU extended timestamp descriptor parsing and rewriting unit, and the presentation time of the first MPU after the switch from the MPU timestamp descriptor parsing and rewriting unit. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 is a functional block diagram showing an example of the configuration of a general compression multiplex control device applied to a broadcasting system. [Diagram 2] FIG. 2 is a functional block diagram showing an example of the configuration of a signal switching device to which the signal switching method according to the embodiment of the present invention is applied (when MMTP packets before and after switching are input from the same interface). [Diagram 3] FIG. 3 is a diagram showing the data structure of an MMTP packet defined in ARIB STD-B60. [Figure 4] FIG. 4 is a diagram showing the data structure of the MPU time stamp descriptor defined in ARIB STD-B60. [Diagram 5] FIG. 5 is a diagram showing the data structure of an MPU extended time stamp descriptor defined in ARIB STD-B60. [Figure 6] FIG. 6 is a diagram showing the data structure of the MMTP payload defined in ARIB STD-B60. [Figure 7] FIG. 7 is a functional block diagram showing an example of the configuration of an MMTP processing unit in the case where MMTP packets before and after switching are input from different interfaces. [Figure 8] FIG. 8 is a timing diagram showing a method for determining the last MPU before switching and the first MPU after switching performed by the MMTP packet selector in operation example A. [Figure 9] FIG. 9 is a diagram showing the structure of an SOP (when reordering is applied). [Figure 10] FIG. 10 is a diagram showing the structure of an SOP (when reordering is not applied). [Figure 11] FIG. 11 is a timing diagram showing a method of determining the last MPU before switching and the first MPU after switching performed by the MMTP packet selector in operation example B. [Figure 12] FIG. 12 is a diagram showing an example of the configuration of an MPU extended time stamp descriptor for explaining the operation example C. [Figure 13] FIG. 13 is a diagram showing a state in which packets are input in time series. [Figure 14] FIG. 14 is a timing diagram showing a method of determining the last MPU before switching and the first MPU after switching performed by the MMTP packet selector in operation example F. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the drawings used in the following description of each embodiment, the same reference numerals are used to denote the same parts, thereby avoiding duplicated description.

[0012] A signal switching device to which a signal switching method according to an embodiment of the present invention is applied will be described.

[0013] A signal switching device to which the signal switching method of the embodiment of the present invention is applied guarantees complete seamlessness on the stream during switching, but allows still images or black screens just before switching, and silence for audio. Furthermore, by using MMT-specific information not present in TS (e.g., "aggregation_flag" included in the MMTP payload, "packet_id" included in the MMTP packet, "mpu_sequence_number", "mpu_presentation_time" included in the MPU timestamp descriptor, "mpu_sequence_number", "mpu_decoding_time_offset", "dts_pts_offset" included in the MPU extended timestamp descriptor, etc.), analysis of the MMTP (MMT Protocol) packet header, MMTP payload header, MPU (Media Processing Unit) timestamp descriptor, and MPU extended timestamp descriptor is eliminated, and switching without image and audio shocks is realized on the broadcasting system side at the receiver.

[0014] FIG. 1 is a functional block diagram showing an example of the configuration of a general compression multiplex control device applied to a broadcasting system.

[0015] The broadcasting system 100 is a broadcasting system (including a distribution system) for terrestrial digital broadcasting, satellite broadcasting, CATV, IP retransmission, and the like.

[0016] The compression multiplexing system control device 110 compresses and encodes the video and audio, generates an MMTP / TLV (MMTP over TLV) that conforms to a predetermined broadcasting method, and outputs it to a transmission facility such as an STL transmission device / OFDM modulator. Here, the predetermined broadcasting method means a broadcasting method that is expected to be developed in the future as terrestrial digital broadcasting methods become more advanced, and new 4K8K satellite broadcasting, etc. Also, the STL transmission device / OFDM modulator of the transmission facility is just one example, and it is also possible to output to the transmission facility using an IP network in the future, so there is no need to specify an output interface to the transmission facility.

[0017] For redundancy purposes, the compression multiplex system control device 110 is equipped with an active system 120A and a standby system 120B having identical configurations, and each of the active system 120A and the standby system 120B is equipped with a plurality of encoders 122 (#1) to (#4), a multiplexer 124, and a scrambler 125.

[0018] The compression multiplex system control device 110 also includes a system switching device 130 provided in common to the active system 120A and the standby system 120B.

[0019] The compression multiplex system control device 110 further includes a plurality of encoders 122 (#1) to (#4), a multiplexer 124, and a synchronization signal generator 140 that distributes a synchronization signal to the system switching device 130.

[0020] The compression multiplexing system control device 110 further includes a frame synchronization signal generator 150 that generates an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) frame synchronization signal and outputs the generated ISDB-T frame synchronization signal to the multiplexer 124. Although ISDB-T frame synchronization is illustrated here, ISDB-S3 frame synchronization or frame synchronization in the case where the ISDB-T system is expanded in the future may also be applied.

[0021] The encoder (HD encoder) 122 (#1), (SD1 encoder) (#2), (SD2 encoder) (#3), and (SD3 encoder) each compress and encode the video and audio, replace the compressed and encoded video and audio with MMTP / TLV (MMTP over TLV) using the synchronization signal output from the synchronization signal generator (#4) 140, and output the converted data to the multiplexer 124.

[0022] The multiplexer 124 multiplexes the video and audio compressed and encoded by each encoder 122 (#1), (#2), (#3), (#4) into a broadcast TS signal having an ISDB-T frame structure using the synchronization signal output from the synchronization signal generator 140 and the ISDB-T frame synchronization signal output from the frame synchronization signal generator 150, and outputs the multiplexed signal to the scrambler 125.

[0023] The scrambler 125 scrambles the MMT or MMTP / TLV output from the multiplexer 124, and outputs the scrambled MMT or MMTP / TLV to the system switching device 130.

[0024] The system switching device 130 performs frame phase adjustment on the MMT or MMTP / TLV output from the scrambler 125 using the synchronization signal output from the synchronization signal generator 140, and outputs the frame phase adjusted MMT or MMTP / TLV to transmission equipment such as an STL transmission device or an OFDM modulator.

[0025] A signal switching device to which the signal switching method according to the embodiment of the present invention is applied is provided between each encoder 122 and a multiplexing device 124 in a compression multiplex system control device 110 as shown in Fig. 1. Alternatively, it can be incorporated into the multiplexing device 124.

[0026] Furthermore, the signal switching device to which the signal switching method of the embodiment of the present invention is applied is not limited to being applied to the compression multiplex system control device 110 as shown in FIG. 1 in order to realize program switching between a streamer that records material encoded for broadcast in advance and a live encoder, or between streamers, but can also be incorporated into a streamer.

[0027] FIG. 2 is a functional block diagram showing an example of the configuration of a signal switching device to which the signal switching method according to the embodiment of the present invention is applied (when MMTP packets before and after switching are input from the same interface).

[0028] The signal switching device 10 illustrated in Figure 2 is an example configuration in which MMTP packets before and after switching are input from the same interface, and comprises an MMTP processing unit 20, an MPT processing unit 30, an MMTP packet buffer (for insertion) 40, an MMTP packet selection unit 50, and an MMTP packet reading control unit 60, the MMTP processing unit 20 further comprises an MMTP packet header analysis unit 22, an MMTP payload header analysis unit 24, an MMTP packet buffer (before switching) 26, and an MMTP packet buffer (after switching) 28, and the MPT processing unit 30 further comprises an MPU timestamp descriptor analysis and rewrite unit 32 and an MPU extended timestamp descriptor analysis and rewrite unit 34.

[0029] The MMTP packet header analysis unit 22 separates pre-switching and post-switching MMTP packet (MPU) and PA message (MPT) packets from the pre-switching IP data flow / packet_ID a and post-switching IP data flow / packet_ID b sent from the upstream side (for example, the encoder 122 shown in Figure 1 or a streamer not shown).

[0030] FIG. 3 is a diagram showing the data structure of an MMTP packet defined in ARIB STD-B60.

[0031] The pre-switching and post-switching IP data flows sent from the upstream side include the MPU timestamp descriptor and the MPU extended timestamp descriptor specified in ARIB STD-B60.

[0032] FIG. 4 is a diagram showing the data structure of the MPU time stamp descriptor defined in ARIB STD-B60.

[0033] FIG. 5 is a diagram showing the data structure of an MPU extended time stamp descriptor defined in ARIB STD-B60.

[0034] FIG. 6 is a diagram showing the data structure of the MMTP payload defined in ARIB STD-B60.

[0035] The MMTP payload header analysis unit 24 obtains the MPU number of each MPU from "mpu_sequence_number" of the MPU timestamp descriptor (Fig. 4) of each MPU separated by the MMTP packet header analysis unit 22, and outputs an MMTP packet with the access unit number counter initialized to zero at the change point of each MPU number. If the MMTP packet is from before switching, the output destination is MMTP packet buffer (before switching) 26, and if it is from after switching, the output destination is MMTP packet buffer (after switching) 28. The counter is incremented each time "aggregation_flag" = 1 is found in the MMTP payload (Fig. 6). "aggregation_flag" = 1 indicates the start of a new video access unit.

[0036] The MPU timestamp descriptor analysis and rewriting unit 32 in the MPT processing unit 30 obtains each MPU number "mpu_sequence_number" and the first presentation time "mpu_presentation_time" of the access unit contained in each MPU from the MPU timestamp descriptor (Figure 4) contained in the PA message (MPT) packet separated by the MMTP packet header analysis unit 22.

[0037] The MPU extended timestamp descriptor analysis and rewriting unit 34 in the MPT processing unit 30 calculates the presentation time of each access unit from the MPU number and "mpu_decoding_time_offset" of each MPU and the "dts_pts_offset" assigned to each access unit of each MPU in the MPU extended timestamp descriptor (Figure 5), and calculates the presentation time of the last access unit of each MPU.

[0038] The MMTP packet read control unit 60 outputs the output from the MPU extended time stamp descriptor analyzing and rewriting unit 34 to the MMTP packet selection unit 50 in accordance with the switching time c.

[0039] The MMTP packet buffer (for insertion) 40 buffers MMTP packets for insertion. The MMTP packet for insertion is inserted when there is a gap between the access unit (A) of the last presentation time of the MPU before switching and the access unit (B) of the first presentation time of the MPU after switching. The gap means, for example, in the case of a video of 60 frames / second, when the time difference between A and B is greater than 1 / 60 seconds (N / 60 seconds, N≧2). The packet for insertion is, for example, a black screen, a specific still image or video, or, for example, silence, which is encoded in advance and converted into an MMTP packet. In the above example, (N-1) video frames are encoded, or one video frame is encoded and concatenated (N-1) times to form an MMTP packet for gap period insertion. The MMTP packet buffer (for insertion) 40 may store MMTP packets for insertion corresponding to different N or encoded different video or audio, and it may be specified from the outside which one to use for insertion.

[0040] The MMTP packet selection unit 50 selects and outputs the last MMTP packet before switching from the MMTP packet buffer (before switching) 26 and the first MMTP packet after switching from the MMTP packet buffer (after switching) 28 based on the switching time c input via the MMTP packet reading control unit 60, the time of the last MPU before switching presented by the MPU extended timestamp descriptor analyzing and rewriting unit 34, and the time of the first MPU after switching presented by the MPU timestamp descriptor analyzing and rewriting unit 32.

[0041] When an MMTP packet is inserted between the MMTP packet before switching and the MMTP packet after switching, the MMTP packet to be inserted is received from MMTP packet buffer (for insertion) 40, and the last MMTP packet before switching, the MMTP packet to be inserted, and the first MMTP packet after switching are output in that order.

[0042] FIG. 7 is a functional block diagram showing an example of the configuration of an MMTP processing unit in the case where MMTP packets before and after switching are input from different interfaces.

[0043] When the MMTP packets before and after switching are input to the signal switching device 10 from different interfaces, the configuration of the MMTP processing unit 20 is replaced with an MMTP processing unit 20a shown in FIG.

[0044] In Figure 7, MMTP packet header analysis unit 22 (#1), MMTP payload header analysis unit 24 (#1), and MMTP packet buffer (before switching) 26 constitute a system that processes MMTP packets before switching, and MMTP packet header analysis unit 22 (#2), MMTP payload header analysis unit 24 (#2), and MMTP packet buffer (after switching) 28 constitute a system that processes MMTP packets after switching.

[0045] The MMTP packet header analysis unit 22 (#1) and the MMTP payload header analysis unit 24 (#1) perform the same processing as the MMTP packet header analysis unit 22 and the MMTP payload header analysis unit 24 on the MMTP packets before the switching, and the MMTP packet header analysis unit 22 (#2) and the MMTP payload header analysis unit 24 (#2) perform the same processing as the MMTP packet header analysis unit 22 and the MMTP payload header analysis unit 24 on the MMTP packets after the switching.

[0046] Next, an example of the operation of the signal switching device 10 having such a configuration will be described.

[0047] (Example A) In operation example A, the MPU timestamp descriptor analysis and rewriting unit 32 interprets the MPU timestamp descriptor (Figure 4), and the MPU extended timestamp descriptor analysis and rewriting unit 34 interprets the MPU extended timestamp descriptor (Figure 5) to recognize the presentation time of each access unit contained in an MPU of a certain MPU number for the MMT stream before and after switching, and the MMTP packet selection unit 50 determines the MPU including switching time c in the MMT stream after switching as the MPU to be sent first after switching, and determines the last MPU before switching so that the final presentation time of the MPUs constituting the MMT stream before switching is before the first presentation time of that MPU.

[0048] FIG. 8 is a timing diagram showing a method for determining the last MPU before switching and the first MPU after switching performed by the MMTP packet selector in operation example A.

[0049] That is, as shown in FIG. 8, based on the presentation periods of each of the MPUs before switching and after switching (in this case, the MPUs before switching are a1 to a3, and the MPUs after switching are b1 to b3), the MMTP packet selection unit 50 determines the MPU after switching that includes switching time c (in this case, b3) as the first MPU after switching, and identifies the last MPU before switching so as not to overlap with the presentation period of the last MPU before switching.

[0050] Such a specific example will be described using switching example 1 and switching example 2 in Fig. 8. Switching example 1 is a case where the MPU immediately before switching (a2 in this case) is presented, and switching example 2 is a case where the MPU before that (a1 in this case) is presented. In this case, in the switching example 1, the last MPU before switching is a2, and in the switching example 2, the last MPU before switching is a1. In both Switching Example 1 and Switching Example 2, the last MPU before switching does not overlap with b3, which is the first MPU after switching.

[0051] When the last MPU before switching is determined, a time obtained by subtracting a predetermined time from the first presentation time of the MPU after switching (going back in time) may be used.

[0052] In this way, the MMTP packet selector 50 analyzes the MMT inputs before and after switching from a time that is a predetermined time back from the specified switching time c, checks the MPU breaks (boundaries) and the presentation periods of each MPU from the MPU timestamp descriptor and the MPU extended timestamp descriptor, and selects the MPU before switching and the MPU after switching so that the presentation periods and the transmission timing of the MMT stream do not overlap and the MPU after switching includes the specified switching time. This applies to both video and audio.

[0053] (Example B) In operation example B, when analyzing the presentation period of the MPU before switching, the SOP (Structure Of Picture) structure in the MPU (GOP (Group Of Picture)) is examined from the MPU extended time stamp descriptor (Fig. 5) to find the picture that is the break (boundary) of the SOP, and the MPU before switching and the SOP boundary within that MPU are found so that the presentation of that SOP ends before the switching time and the transmission timing of that SOP does not overlap with the transmission timing of the MPU after switching. This applies to video.

[0054] Specifically, the MPU timestamp descriptor analysis and rewriting unit 32 and the MPU extended timestamp descriptor analysis and rewriting unit 34 of the MPT processing unit 30 determine the presentation time of each access unit in the MPU before the switch from the MPU timestamp descriptor (Figure 4) and MPU extended timestamp descriptor (Figure 5) for that MPU (corresponding to the MPU number), and the MMTP packet selection unit 50 determines the picture that marks the break (boundary) of the SOP, and determines the MPU before the switch and the SOP boundary within that MPU so that the end of SOP presentation is before the switch time and the timing of the SOP transmission does not overlap with the timing of the MPU after the switch.

[0055] FIG. 9 is a diagram showing the structure of an SOP (when reordering is applied).

[0056] FIG. 10 is a diagram showing the structure of an SOP (when reordering is not applied).

[0057] FIG. 11 is a timing diagram showing a method of determining the last MPU before switching and the first MPU after switching performed by the MMTP packet selector in operation example B.

[0058] In the case of the hierarchical B structure as shown in Fig. 9, the coding order (transmission order) and the presentation order are swapped, and the access units up to the SOP boundary are consecutive in the presentation order. Therefore, after obtaining the presentation time of each access unit, they are arranged in ascending order, and the SOP boundary is the access unit whose presentation time is consecutively arranged from the presentation time indicated by the MPU timestamp descriptor (switching example 1 in Fig. 11). Note that in the structure as shown in Fig. 10, SOP can be terminated at the boundary of all access units. Based on the SOP boundary obtained here, the final SOP in the final MPU before switching is decided so that packet transmission before and after switching does not overlap (switching example 2 in Fig. 11).

[0059] (Example C) Operation example C is applied to video. The number of access units in the final MPU before switching buffered in the MMTP packet buffer (before switching) 26 is less than that of the original MPU. Therefore, the MPU extended time stamp descriptor analyzing and rewriting unit 34 reduces the number of access units in the MPU extended time stamp descriptor (FIG. 5) and deletes it so that only the information of the access units included in the final SOP is included.

[0060] FIG. 12 is a diagram showing an example of the configuration of an MPU extended time stamp descriptor for explaining the operation example C.

[0061] The MPU extended time stamp descriptor analyzing and rewriting unit 34 deletes information about the access units after the obtained SOP boundary as the MPU extended time stamp descriptor corresponding to the MPU before switching buffered in the MMTP packet buffer (before switching) 26, as shown in Fig. 12, and sends it to the MMTP packet selecting unit 50. This makes it possible to delete unnecessary descriptors (that will no longer be used due to switching) from the MPT asset loop when multiple MPU time stamp descriptors (Fig. 4) and MPU extended time stamp descriptors (Fig. 5) are included in the MPT.

[0062] (Example D) Operation example D is applied to video, and determines how many (N) access units from the beginning of the MPU the determined SOP boundary includes, counts the number of packets from the beginning of the MPU whose "aggregation_flag" in the MMTP payload header is set to 1, and stops sending from the (N+1)th packet.

[0063] Specifically, the MMTP payload header analysis unit 24 analyzes an MMTP packet (asset) with the same IP data flow and the same packet_id, and when the "mpu_sequence_number" changes, it initializes the number of access units in the MPU to 0, and thereafter increments the number of access units each time it finds an MMTP packet with "aggregation_flag=1".

[0064] The MMTP packet selection unit 50 compares this result with the number of access units in the MPU up to the SOP boundary calculated in operation example B, and once it has finished sending out up to the last access unit of the last SOP before switching, it stops reading from the MMTP packet buffer (before switching) and waits to read from the MMTP packet buffer (after switching).

[0065] Note that non-VCL NAL units are always present at the beginning of an access unit, and are not present anywhere else. Therefore, an MMTP packet containing an MMTP payload with "aggregation_flag" set to 1 is the beginning of an access unit. Note that parsing an MMTP packet for each packet-ID is self-evident from the MMT standard.

[0066] (Example D') Operation example D' is applied to video, and the MMTP payload header analysis unit 24, for each MPU separated by the MMTP packet header analysis unit 22, notices that the "fragmentation_indicator" of the MMTP payload (Figure 6) indicates a certain specific value, identifies the beginning, end, or somewhere else (it may be both the beginning and the end) of the video, and does not count the next "aggregation_flag".

[0067] By recognizing the "fragmentation_indicator", the end of the video can be recognized earlier than by recognizing it using the "aggregation_flag" as in operation example D.

[0068] This principle will be explained with reference to FIG.

[0069] FIG. 13 is a diagram showing a state in which packets are input in time series.

[0070] In FIG. 13, one video packet is made up of one leading non-VCL packet indicated by a hatched rectangular block, and one or more subsequent VCL packets indicated by non-hatched blocks.

[0071] Non-VCL packets have "aggregation_flag"=1 set. In operation example D, the MMTP packet selector 50 identifies a cluster of video packets by identifying the "aggregation_flag". Therefore, in the case of operation example D, to recognize the end of a video packet, it is necessary to recognize the first "aggregation_flag" of the next video packet. For example, to recognize the end of the fourth video packet 4, this is done by recognizing the "aggregation_flag" of the fifth video packet 5.

[0072] However, in the operational example D', a fragment of video packets is identified by a "fragmentation_indicator" rather than an "aggregation_flag".

[0073] For MMTP packets containing an MPU, a "fragmentation_indicator" is set in the MMTP payload header, with "01" indicating the first packet of the fragment, "10" indicating a packet that is neither the first nor the last, "11" indicating the last packet, and "00" indicating a packet that contains one or more NAL units.

[0074] That is, it is possible to detect the end of an access unit by recognizing that the "fragmentation_indicator" is "11" or "00" in a VCL packet with "aggregation_flag" = 0, and it is possible to determine the end of the packet cluster that constitutes a video access unit before receiving and recognizing the "aggregation_flag" of a non-VCL packet that appears at the beginning of the next access unit. This is an effective means of determination when the amount of video code is small, such as in the case of a black screen, and as a result the interval between packets is long.

[0075] In this way, the MMTP payload header analysis unit 24 can recognize the end of the video earlier than in the case of operation example D.

[0076] (Example E) Operation example E is applied to video, and the MMTP packet selection unit 50 obtains the presentation period of the MPU from the MPU timestamp descriptor (Figure 4) and the MPU extended timestamp descriptor (Figure 5) to check whether the switched MPU includes the specified switching time.

[0077] (Example F) FIG. 14 is a timing diagram showing a method of determining the last MPU before switching and the first MPU after switching performed by the MMTP packet selector in operation example F.

[0078] In the operation example F, which is applied to video, the MPU before switching (or the SOP in the MPU) cannot be sent until the end timing of the sending of the MPU before switching (or the SOP in the MPU) is known, so an MMTP packet buffer (before switching) 26 is provided to buffer the MPU before switching (or the SOP in the MPU) and realize a fixed delay. If the last MPU before switching in FIG. 14 is sent and the MPU including the switching time after switching is also sent, there will be two video frames to be presented at the same presentation time. This operation example is intended to prevent such a situation. In addition, in video coding, the amount of code after coding differs depending on the picture type of each frame, so even if the presentation timing of the video does not overlap, the sending timing of the MMTP stream (the timing input to the MMTP packet selection unit) may overlap. In such a case, the MMTP packets before and after switching are sent alternately (N times before switching → M times after switching → L before switching → K times after switching →...), so normal reception and playback will not be possible. Therefore, to prevent the MMTP stream before switching from overlapping with the transmission timing of the MMTP stream after switching, buffering is performed in this buffer, and the frame position at which to terminate the MPU (or SOP within the MPU) before switching is determined.

[0079] (Example G) Operation example G is applied to video, and the MMTP packet selection unit 50 obtains the presentation time of the last video frame to be presented in the MPU (or SOP within the MPU) before switching and the presentation time of the first video frame to be presented after switching from the MPU extended timestamp descriptor (Figure 4), and if there are any missing frames between the two, an MPU that has been created in advance by encoding and multiplexing a specified image is inserted from the MMTP packet buffer (for insertion) 40.

[0080] This is a measure to avoid the possibility of a shock to the receiver caused by a gap in the presented audio-video frames when switching between operation examples B and F.

[0081] When an audiovisual frame presented due to switching is lost, such as in operation example B (switching example 2 shown in FIG. 8) or operation example F (switching example 1 in FIG. 8), a predetermined audiovisual signal that has been encoded in advance is read from the MMTP packet buffer (for insertion) 40 and inserted. The predetermined audiovisual signal is a black screen, a still image screen at the end / start of a program, silence, etc., and the appropriate signal is selected based on the program information and the number of audiovisual frames to be inserted, etc.

[0082] (Example H) Operation example H is applied to video and is a method of correcting the time information in the MPU timestamp descriptor to maintain the continuity of the presentation time when an MMTP packet is inserted in operation example G. The presentation time of the inserting MPU and the MPU after switching is set or corrected so that it is the time obtained by adding an integer multiple of the time calculated from the frame rate based on the presentation time of the last video frame of the MPU before switching.

[0083] Specifically, if the difference between the presentation times of each video / audio frame of the MPU before and after the switching is not a predetermined time calculated from the video frame rate or a predetermined time calculated from the number of samples in the audio frame and the sampling frequency, the MPU timestamp descriptor analyzing / rewriting unit 32 corrects the presentation time in the MPU timestamp descriptor of the MPU after the switching. The same is done for the MPU to be inserted. If it is determined that a correction of one or more frames is necessary, the number of frames of the MPU to be inserted is reduced by one frame to keep the deviation from the initially expected presentation time to within one frame.

[0084] (Example I) Operation example I is applied to audio, and the MMTP packet selection unit 50 determines the presentation time of the last audio frame to be presented in the MPU before switching and the presentation time of the first audio frame to be presented after switching from the MPU timestamp descriptor (Figure 4) and the MPU extended timestamp descriptor (Figure 5).If there are missing frames between the two, an MPU that was previously created by encoding and multiplexing silent audio is inserted from the MMTP packet buffer (for insertion) 40.

[0085] This effect is similar to that of operational example G, so a duplicated explanation will be avoided.

[0086] (Operation example J) Operation example J is applied to audio, and in operation example I, the presentation times of the MPU to be inserted and the MPU after switching are set or corrected so that they are the time obtained by adding an integer multiple of the time corresponding to the audio frame based on the presentation time of the last audio frame of the MPU before switching.

[0087] Specifically, if the difference in presentation time between each video / audio frame of the MPU before and after switching is not a predetermined time calculated from the video frame rate or a predetermined time calculated from the number of samples in an audio frame and the sampling frequency, the MPU timestamp descriptor analysis and switching unit 32 corrects the presentation time ("mpu_presentation_time") in the MPU timestamp descriptor (FIG. 4) of the MPU after switching. The same is done for the MPU to be inserted. If it is determined that a correction of one or more frames is necessary, the number of frames of the MPU to be inserted is reduced by one frame to keep the deviation from the initially expected presentation time to within one frame.

[0088] This effect is similar to that of operational example H, so a duplicate explanation will be avoided.

[0089] As described above, according to the signal switching device to which the signal switching method of the present embodiment is applied, it is possible to switch between a streamer, whose GOP start position and code amount are determined in advance at the time of recording, and an encoder or a streamer, simply by analyzing the MMT layer. Therefore, the encoder does not need to operate in baseband or control the GOP start position and code amount, and it is possible to switch programs or switch redundant systems without any shock to the image or sound when switching.

[0090] 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]

[0091] 10··signal switching device, 20, 20a··MMTP ​​processing unit, 22··MMTP ​​packet header analysis unit, 24··MMTP ​​payload header analysis unit, 26··MMTP ​​packet buffer (before switching), 28··MMTP ​​packet buffer (after switching), 30··MPT processing unit, 32··MPU time stamp descriptor analysis and rewriting unit, 34··MPU extended time stamp descriptor analysis and rewriting unit, 40··MMTP ​​packet buffer (for insertion), 50··MMTP ​​packet selection unit, 60··MMTP ​​packet read control unit, 100··broadcasting system, 110··compression multiplex system control device, 120A··active system, 120B··standby system, 122··encoder, 124··multiplexing device, 125··scrambler, 130··system switching device, 140··synchronization signal generator, 150··frame synchronization signal generator

Claims

1. A signal switching device for switching from a pre-switching IP data flow to a post-switching IP data flow, an MMTP packet header analysis unit that refers to an IP data flow and packet_id sent from the upstream side, and separates packets of assets constituting an MPU (Media Processing Unit) and packets of a PA (Package Access) message including an MPT (MMT Package Table) from MMTP (MPEG Media Transport Protocol) packets before and after the switching; an MMTP payload header analysis unit that acquires an MPU number of each MPU from an MPU timestamp descriptor of each MPU separated by the MMTP packet header analysis unit, and outputs an MMTP packet in which an access unit number counter is initialized to zero at a change point of each MPU number; an MPU time stamp descriptor analysis and rewriting unit that acquires each MPU number separated by the MMTP packet header analysis unit and the first presentation time of an access unit included in each MPU from the MPU time stamp descriptor; an MPU extended time stamp descriptor analyzing and rewriting unit that obtains an MPU number of each MPU and a presentation time of each access unit of the MPU from the MPU extended time stamp descriptor of each MPU, and further obtains a final presentation time of each access unit; A signal switching device comprising an MMTP packet selection unit that selects the last MMTP packet before switching and the first MMTP packet after switching based on a specified switching time, the presentation time of the last MPU before switching from the MPU extended time stamp descriptor analysis and rewriting unit, and the presentation time of the first MPU after switching from the MPU time stamp descriptor analysis and rewriting unit.

2. the MPU time stamp descriptor analysis and rewriting unit recognizes the presentation time of each access unit included in an MPU of a certain MPU number by interpreting the MPU extended time stamp descriptor, for MMT (MPEG Multimedia Transport) streams before and after the switching; The signal switching device of claim 1, wherein the MMTP packet selection unit determines the last MPU before the switching so that in the MMT stream after the switching, the MPU including the switching time is the MPU to be sent first after the switching, and the last presentation time of the MPU constituting the MMT stream before the switching is before the first presentation time of that MPU.

3. the MPU time stamp descriptor analyzing / rewriting unit and the MPU extended time stamp descriptor analyzing / rewriting unit obtain a presentation time of each access unit in an MPU before switching from the MPU time stamp descriptor and the MPU extended time stamp descriptor corresponding to the MPU number for the MPU; The signal switching device of claim 1, wherein the MMTP packet selection unit determines a picture that is a SOP boundary, and determines the MPU before switching and the SOP boundary within that MPU so that the presentation of the SOP ends before the switching time and the sending timing of the SOP does not overlap with the sending timing of the MPU after the switching.

4. The signal switching device of claim 3, wherein the MPU extended time stamp descriptor analysis and rewriting unit sends to the MMTP packet selection unit the MPU extended time stamp descriptor corresponding to the MPU before switching, with information of access units after the SOP boundary deleted.

5. The MMTP payload header analysis unit analyzes MMTP packets having the same IP data flow and the same packet_id, and initializes the number of access units in the MPU to 0 when the "mpu_sequence_number" changes. Thereafter, the number of access units is incremented each time an MMTP packet with "aggregation_flag = 1" is found. The signal switching device of claim 3, wherein the MMTP packet selection unit compares the incremented number with the number of access units in the MPU up to the SOP boundary, and when transmission up to the last access unit of the last SOP before the switching is completed, stops reading the MMTP packets before the switching and waits for reading from the MMTP packet buffer after the switching.

6. The signal switching device of claim 3, wherein the MMTP payload header analysis unit recognizes the end of a video packet by recognizing the value of a "fragmentation_indicator" in the MMTP payload for each MPU separated by the MMTP packet header analysis unit.

7. The signal switching device of claim 1, wherein the MMTP packet selection unit determines the presentation period of the MPU from the MPU timestamp descriptor and the MPU extended timestamp descriptor to check whether the MPU after switching includes the switching time.

8. The signal switching device according to claim 1 , further comprising a pre-switching MMTP packet buffer for storing the pre-switching MPU until the timing of the end of transmission of the pre-switching MPU is determined.

9. Further comprising an insertion MMTP packet buffer storing an MPU created in advance by encoding and multiplexing a predetermined image, A signal switching device as described in claim 1, wherein when there is a missing frame between the presentation time of the last video frame to be presented in an MPU before switching and the presentation time of the first video frame to be presented after switching, the MMTP packet selection unit inserts an MPU stored in the MMTP packet buffer for insertion into the missing frame.

10. A signal switching device as described in claim 1, wherein if the difference in presentation time of each video / audio frame of the MPU before and after switching is not a predetermined time calculated from the video frame rate or a predetermined time calculated from the number of samples in the audio frame and the sampling frequency, the MPU timestamp descriptor analysis and rewriting unit corrects the presentation time in the MPU timestamp descriptor of the MPU after switching.

11. Further comprising an insertion MMTP packet buffer for storing an MPU created in advance by encoding and multiplexing silent audio, A signal switching device as described in claim 1, wherein when there is a missing frame between the presentation time of the last audio frame to be presented in an MPU before switching and the presentation time of the first audio frame to be presented after switching, the MMTP packet selection unit inserts an MPU stored in the MMTP packet buffer for insertion into the missing frame.

12. A signal switching device as described in claim 1, wherein if the difference in presentation time of each video / audio frame of the MPU before and after switching is not a predetermined time calculated from the video frame rate or a predetermined time calculated from the number of samples in the audio frame and the sampling frequency, the MPU timestamp descriptor analysis and rewriting unit corrects the presentation time in the MPU timestamp descriptor of the MPU after switching.

13. A signal switching method executed by a signal switching device to switch from a pre-switching IP data flow to a post-switching IP data flow, comprising: The signal switching device, By referring to the IP data flow and packet_id sent from the upstream side, the packet of the asset constituting the MPU (Media Processing Unit) and the packet of the PA (Package Access) message including the MPT (MMT Package Table) are separated from the MMTP (MPEG Media Transport Protocol) packets before and after the switching, and obtain an MPU number of each of the separated MPUs from an MPU timestamp descriptor of each of the separated MPUs, and output an MMTP packet in which a counter for the number of access units is initialized to zero at a change point of each of the MPU numbers; Obtaining each of the separated MPU numbers and the first presentation time of the access unit included in each of the MPUs from the MPU timestamp descriptor; obtaining an MPU number of each of the MPUs and a presentation time of each of the access units of the MPU from the MPU extended time stamp descriptor of each of the MPUs, and further obtaining a final presentation time of each of the access units; A signal switching method that selects the last MMTP packet before switching and the first MMTP packet after switching based on a specified switching time, the presentation time of the last MPU before the switching, and the presentation time of the first MPU after the switching.

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