JP4491970B2 - Digital signal multiplexer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention multiplexes digital signals such as video and audio to generate a primary multiplexed stream including a program such as a television or radio program, and further secondary-multiplexes the one or more primary multiplexed streams. The present invention relates to a digital signal multiplexing apparatus and method for generating a secondary multiplexed stream.
[0002]
[Prior art]
A transport stream for multiplexing and transmitting one or more programs (for example, services in which broadcast programs in television broadcasting are continuously organized) into one multiplexed stream is defined in ISO / IEC13818-1. Conventionally, a multiplexing system for generating this transport stream is known.
[0003]
FIG. 11 shows an example of a broadcast system configuration for transmitting a transport stream using digital broadcasting or the like.
[0004]
The transmission apparatus 100 is supplied with baseband video data and audio data corresponding to a plurality of programs, data not shown, or the like from a server, a video camera, or the like. The video data and audio data are supplied to the video encoder 111 (111-1 to 111-n) and the audio encoder 112 (112-1 to 111-n) corresponding to each program, for example, MPEG-2 (ISO / It is encoded into a compressed data stream (elementary stream) corresponding to IEC11172, ISO13818) or the like.
[0005]
Each encoded elementary stream is supplied to a primary multiplexer 113 (113-1 to 113-n) corresponding to each program. Each primary multiplexer 113 time-division-multiplexes elementary streams supplied for each program in units of transport packets (TS packets) defined by ISO / IEC13818-1, and performs primary multiplexing corresponding to each program. Generate a stream.
[0006]
A plurality of primary multiplexed streams generated by the primary multiplexers 113 are supplied to the secondary multiplexer 114. The secondary multiplexer 114 further time-division-multiplexes a plurality of primary multiplexed streams in units of TS packets to generate one secondary multiplexed stream.
[0007]
The secondary multiplexer 114 supplies the generated secondary multiplexed stream to the receiving apparatus 300 via the transmission medium 200.
[0008]
Here, the primary multiplexed stream and the secondary multiplexed stream multiplexed by each primary multiplexer 113 and secondary multiplexer 114 correspond to the transport stream defined in ISO / IEC13818-1.
[0009]
As described above, the transmission apparatus 100 compresses and encodes baseband video data and audio data corresponding to each program to generate one secondary multiplexed stream, and the generated secondary multiplexed stream is transmitted to the transmission medium 200. To the receiving device 300.
[0010]
The secondary multiplexed stream is transmitted to the receiving apparatus 300 via the transmission medium 200. The secondary multiplexed stream is supplied to the separator 311. For example, the separator 311 separates only the elementary stream corresponding to the program designated by the viewer or the like from the secondary multiplexed stream and supplies the separated stream to the video decoder 312 and the audio decoder 313. That is, the separator 311 supplies the video elementary stream of the designated program to the video decoder 312 and supplies the audio elementary stream of the designated program to the audio decoder 313.
[0011]
The video decoder 312 and the audio decoder 313 respectively perform decompression decoding processing corresponding to the compression-encoded data, generate baseband video data and audio data, and supply them to an external device (not shown).
[0012]
As described above, the receiving apparatus 300 receives the supplied secondary multiplexed stream, selects a predetermined program from a plurality of programs included in the secondary multiplexed stream, and performs a decoding process.
[0013]
FIG. 11 shows an example in which the primary multiplexer generates a transport stream consisting of one program consisting of video and audio, but the program is not limited to a combination of video and audio, and In some cases, a plurality of programs are multiplexed in the transport stream output from the primary multiplexer.
[0014]
FIG. 12 shows the data structure of the primary multiplexed stream and the secondary multiplexed stream, which are transport streams defined by ISO / IEC13818-1.
[0015]
Each primary multiplexer divides the video elementary stream encoded by the video encoder and the audio elementary stream encoded by the audio encoder into TS packets having a fixed length of 188 bytes. A primary multiplexing process is performed by time division to generate a primary multiplexed stream. Subsequently, the secondary multiplexer further performs secondary multiplexing processing on each primary multiplexed stream in a time division manner in units of the TS packets to generate a secondary multiplexed stream. Thus, the primary multiplexed stream and the secondary multiplexed stream have a stream configuration multiplexed in units of TS packets.
[0016]
FIG. 13 shows the data structure of the TS packet. The TS packet has a total data of 188 bytes, and includes a fixed header, an optional adaptation field, and data bytes. In the adaptation field, a time reference reference value (PCR: Program Clock Reference), a stuffing_byte for size adjustment, and the like are encoded.
[0017]
PCR is a time base reference value that represents the arrival time of data (that is, the output time of data in the multiplexer). In the receiving apparatus, the system clock of the transmitting apparatus is restored by performing, for example, PLL synchronization using this PCR.
[0018]
FIG. 14 shows a decoder model of the receiving apparatus 300 when the transport stream defined by the above-mentioned ISO / IEC13818-1 is supplied. When a transport stream defined by ISO / IEC13818-1 is generated, TS packets are scheduled and time division multiplexed so that processing in the decoder model shown below does not fail.
[0019]
For example, the separator 311 selects only TS packets corresponding to the program designated by the viewer from the secondary multiplexed stream, and distributes them to the transport buffers 304 to 306. Each transport buffer 304 to 306 stores a TS packet of corresponding data. For example, the transport buffer 304 stores TS packets of video data of the selected program, the transport buffer 305 stores TS packets of audio data of the selected program, and the transport buffer 306 is selected. The TS packet of the program control data for the selected program is stored. Although a transport buffer for data other than audio and video is not shown here, if data is included in the selected program, these TS packets are stored in the corresponding transport buffer.
[0020]
Each of the transport buffers 304 to 306 has a capacity of 512 bytes, for example, and leaks data_byte of the TS packet at a prescribed bit rate as long as data is stored.
[0021]
The video data leaked from the transport buffer 304 is supplied to the multiplexing buffer 307. The audio data and program control data leaked from the transport buffers 305 and 306 are supplied to the corresponding elementary buffers 309 and 310, respectively.
[0022]
From the multiplexing buffer 307, only the elementary stream leaks at the prescribed bit rate and is supplied to the elementary buffer 308. The decoders 311, 312, and 313 extract the elementary stream from the corresponding elementary buffer for each decoding unit called “access unit” (picture unit in the case of video data) at each decoding time, and perform decoding processing. The video data decoding process is performed using the reorder buffer 314 in order to display the screen in time series. The decoded baseband video data, audio data, and control data are respectively supplied to an external device or a system controller.
[0023]
In the receiving apparatus 300, the transport stream decoding process defined by the above-mentioned ISO / IEC13818-1 is performed using the above model. As described above, it is possible to transmit a transport stream obtained by multiplexing data compressed for each of a plurality of programs by the transmission device 100, and to separate and decode the data by the reception device 300.
[0024]
The primary multiplexer of the transmission apparatus 100 time-division multiplexes TS packets on a schedule such that each buffer in the decoder model shown in FIG. 14 does not underflow or overflow.
[0025]
By the way, in a multiplexing system such as that used in the above-described broadcasting system, that is, a multiplexing system in which a primary multiplexed stream that has been subjected to primary multiplexing is further multiplexed to generate a single secondary multiplexed stream, Due to the reasons mentioned above, there is a time lag between the output timing of the primary multiplexed stream scheduled by each primary multiplexer and the output timing of the primary multiplexed stream multiplexed in the secondary multiplexed stream. End up.
[0026]
(1) The secondary multiplexing can be performed only in the time slot of TS packet unit at the bit rate of the secondary multiplexed stream.
(2) The bit rate of the secondary multiplexed stream is higher than the bit rate of the primary multiplexed stream.
(3) Since the TS packet that can be secondarily multiplexed into a certain time slot is only one TS packet of the primary multiplexed stream, the TS packet of the primary multiplexed stream output from the primary multiplexer at approximately the same time is kept waiting. End up.
[0027]
Here, a time lag generated between the output timing of the primary multiplexed stream scheduled by each primary multiplexer and the output timing of the primary multiplexed stream multiplexed in the secondary multiplexed stream is reduced to two. This is called next multiplexing jitter.
[0028]
Therefore, in such a multiplexing system, even if the primary multiplexed stream is generated by scheduling so that the decoder buffer provided in the preceding stage of the decoder does not fail by the primary multiplexer, this secondary multiplexed jitter occurs, and the decoder A deviation occurs in the arrival timing of the data stream to the buffer, or a deviation occurs in the time base reference value encoded in the secondary multiplexed stream (PCR if the transport stream is defined in ISO13818-1). Or For this reason, there has been a problem that the decoder buffer fails due to the influence of these shifts.
[0029]
In order to solve the above problem, a pattern that determines the order of time-division multiplexing of TS packets extracted from the primary multiplexed stream is set in advance, and TS packets are sequentially selected from the primary multiplexed stream according to this pattern. Accordingly, the present applicant has proposed a multiplexing method for generating a secondary multiplexed stream without reducing the secondary multiplexing jitter and correcting the time base reference value (PCR) in Japanese Patent Laid-Open No. 11-215083. Yes.
[0030]
The secondary multiplexing method proposed in Japanese Patent Laid-Open No. 11-215083 will be briefly described below with reference to FIG.
[0031]
A plurality of primary multiplexed streams are input to the secondary multiplexer. The secondary multiplexer sets a pattern that defines the selection order of TS packets. This pattern is a predetermined pattern indicating in what order TS packets are extracted from a plurality of primary multiplexed streams and subjected to secondary multiplexing. The secondary multiplexer performs secondary multiplexing by periodically repeating this pattern. Further, the bit rate of each primary multiplexed stream is set based on the number of TS packets of each primary multiplexed stream included in this pattern and the bit rate of the secondary multiplexed stream. For example, when two primary multiplexed streams of program A and program B are multiplexed to generate a 1 Mbps secondary multiplexed stream, three TS packets of program A and one TS packet of program B are included in one pattern. Are included, the program A bit rate is set to 600 kbps, and the program B bit rate is set to 400 kbps. Or conversely, the bit rate of the pattern and the secondary multiplexed stream may be determined based on the bit rate of each primary multiplexer. Each primary multiplexer then adds a PCR to each TS packet number of the primary multiplexed transport stream included in the pattern (for example, in the example of FIG. Program B assigns PCR every 2 TS packets.), It becomes possible to assign PCR to a fixed position in the pattern of the secondary multiplexed stream.
[0032]
Note that the secondary multiplexing delay shown in FIG. 15 is a delay time that occurs fixedly when performing secondary multiplexing. Therefore, even if this secondary multiplexing delay occurs, there is no problem that the decoder buffer fails.
[0033]
In the secondary multiplexing method proposed in Japanese Patent Application Laid-Open No. 11-215083, if the reference clock Cp of the primary multiplexer and the reference clock Cr of the secondary multiplexer are synchronized, Multiplexed jitter occurs only up to a fixed amount fixed in the pattern. Therefore, since the upper limit of the secondary multiplexing jitter can be determined, if the primary multiplexed stream is generated with a margin for the upper limit of the capacity of the decoder buffer assumed in advance, the secondary multiplexing is performed. However, it does not cause a failure in the decoder buffer.
[0034]
However, for example, when the primary multiplexer and the secondary multiplexer are completely different devices, a system configuration in which the reference clock Cp of the primary multiplexer and the reference clock Cr of the secondary multiplexer are asynchronous. Must. In the case of such an asynchronous system, the secondary multiplexing method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 11-215083, for example, continues the secondary multiplexing according to the pattern as shown in FIG. Even so, there is a problem that a secondary multiplexing timing shift (secondary multiplexing jitter) due to a reference clock shift occurs, and the more the multiplexing is advanced, the more the secondary multiplexing jitter is accumulated. is there.
[0035]
That is, when the bit rate P is assigned to each primary multiplexer based on the number of TS packets that are secondarily multiplexed in the pattern, the primary multiplexer is configured to use the bit rate P in the reference clock Cp of the primary multiplexer. The primary multiplexed stream is output, and the secondary multiplexer performs secondary multiplexing of the primary multiplexed stream at the bit rate P at the reference clock Cr of the secondary multiplexer. As described above, when multiplexing is performed using a unique reference clock, errors in the reference clock accumulate as secondary multiplexing jitter as the multiplexing progresses.
[0036]
If the secondary multiplexing jitter accumulates, the buffer in the receiving apparatus overflows or underflows, and the secondary multiplexing timing of PCR shifts, so that the system clock on the transmitting side cannot be correctly restored in the receiving apparatus. Will occur.
[0037]
In order to solve such a problem, a pattern that determines the order of time division multiplexing of TS packets extracted from the primary multiplexed stream is set in advance, and TS packets are selected in order from the primary multiplexed stream according to this pattern. Furthermore, the present applicant has disclosed a multiplexing method in which dummy data is multiplexed and the accumulated secondary multiplexing jitter is canceled when the secondary multiplexing jitter exceeds a certain amount. -215082.
[0038]
The secondary multiplexing method proposed in Japanese Patent Laid-Open No. 11-215082 will be briefly described below with reference to FIG. In the secondary multiplexer, the secondary multiplexing processing proposed in the above-mentioned Japanese Patent Application Laid-Open No. 11-215083 is performed, and further, the secondary multiplexing jitter D (i) is monitored, and this secondary multiplexing is performed. When the jitter D (i) is equal to or greater than the threshold value, a dummy TS packet (for example, NULL TSP defined in ISO / IEC13818-1) is inserted, thereby avoiding the accumulation of shifts in the secondary multiplexing timing. The secondary multiplexer corrects and outputs the PCR in accordance with the secondary multiplexing output timing. Further, in order to be able to correct the secondary multiplexing jitter D (i) by inserting a dummy TS packet (NULL TSP), the bit rate assigned to the primary multiplexer is secondary multiplexed in the pattern. The bit rate is assigned to be smaller than the bit rate P determined based on the number of TS packets. For example, if the maximum system clock rating of the primary multiplexer is CpMAX and the minimum system clock rating of the secondary multiplexer is CrMIN, the bit rate assigned to the primary multiplexer is (CrMIN / By setting CpMAX) * P, the secondary multiplexing timing is always advanced, and correction is possible by inserting a dummy TS packet (NULL TSP).
[0039]
However, in the secondary multiplexing method proposed in Japanese Patent Application Laid-Open No. 11-215082, even if PCR is added to each TS packet number of the primary multiplexed transport stream included in the pattern, secondary multiplexing is performed. By inserting a dummy TS packet (NULL TSP) to correct the timing shift, the position in the pattern of the TS packet to which the PCR is attached is shifted. Alternatively, even if the primary multiplexer assigns PCR every time period corresponding to the pattern, the dummy TS packet (NULL TSP) is inserted to correct the secondary multiplexing timing shift, thereby causing the PCR. Will be out of position in the pattern of TS packets to which.
[0040]
For example, as shown in FIG. 17, when a primary multiplexed stream of program A having a bit rate of 600 kbps is multiplexed to generate a secondary multiplexed stream of 1 Mbps, 3 TS packets of program A are included in one pattern. Will be included. If the primary multiplexer transmits a TS packet to which PCR is attached every 3 packets, the TS to which this PCR is attached at a fixed position in the pattern (the first packet of the pattern in FIG. 17). Packets will be placed. However, when a dummy TS packet (NULL TSP) is inserted, the position where the PCR is arranged is shifted (in FIG. 17, the position of the PCR is shifted from the first packet of the pattern to the third packet). .)
[0041]
[Problems to be solved by the invention]
By the way, in terrestrial digital broadcasting, in order to reduce the influence of reception interference due to multipath, the OFDM method is generally adopted as a modulation method of broadcast waves. The OFDM system is also adopted in ISDB-T (Intergrated Services Digital Broadcasting-Terrestorial), a terrestrial digital broadcasting system in Japan. In the OFDM system, modulation is performed by performing IFFT (Inverse Fast Fourier Transform) at the time of transmission and FFT (Fast Fourier Transform) at the time of reception.
[0042]
In this ISDB-T, a method called partial reception is adopted so that only a signal in a partial frequency band among OFDM signals transmitted in one frequency channel can be received. When broadcasting using this partial reception method, a wideband receiver that can receive all signals of one frequency channel and a narrowband receiver that can receive only a part of signals of one frequency channel, The broadcast can be received. By adopting such a partial reception method, for example, only an audio signal in a television broadcast can be received by an audio receiver, or only main information can be received by a narrowband receiver. When it is desired to receive information, it can be realized by receiving it with a broadband receiver, and the broadcast can be extended.
[0043]
Here, when such a partial reception method is employed, one transport stream is basically broadcast on one frequency channel, but a broadband receiver broadcasts on that frequency channel. This means that all TS packets of a transport stream can be received, whereas a narrowband receiver can receive only a part of the TS packets of the transport stream broadcast on that frequency channel. It will be.
[0044]
For example, as shown in FIG. 18, if six TS packets are transmitted in one symbol, a wideband receiver can receive all six TS packets, but a narrowband receiver Only a part of them (for example, two TS packets) can be received.
[0045]
Therefore, it is necessary to generate a transport stream by multiplexing so as to include PCR so that the system clock can be correctly restored even in some packets received by the narrowband receiver.
[0046]
However, as described above, when a secondary multiplexed stream (transport stream) is generated in such a manner that the secondary multiplexing jitter is adjusted by dummy data, the primary multiplexed stream side periodically performs a fixed packet interval. Even if a PCR is inserted into the TS packet, if a dummy packet is inserted at the time of secondary multiplexing, the position in the pattern of the TS packet to which the PCR is attached is shifted. For this reason, a TS packet to which PCR is attached cannot be inserted at a fixed position in the pattern. Therefore, conventionally, when the partial reception method as described above is adopted, a transport stream that can reliably extract the PCR and restore the system clock when partial reception is performed by a narrowband receiver, It was not possible to transmit from the transmitter side.
[0047]
The present invention has been made in view of such circumstances, and can generate a primary multiplexed stream and a secondary multiplexed stream based on an asynchronous reference clock, and can also generate a fixed number of secondary multiplexed streams. Digital signal multiplexing that can arrange a time base reference value at a position and can reliably restore the system clock to the reception side even in a reception method in which only a part of packets in the secondary multiplexed stream is received An object of the present invention is to provide an apparatus and method.
[0048]
[Means for Solving the Problems]
In the digital signal multiplexing apparatus according to the present invention, the bit stream of the digital signal is multiplexed on a packet basis in a time division manner, and at least one time reference value indicating the output timing of the bit stream is included in the bit stream. A digital signal multiplexing device that receives a primary multiplexed stream from one or more primary multiplexing devices and multiplexes each received primary multiplexed stream in a time division manner in units of packets to generate a secondary multiplexed stream. Receiving means for receiving each primary multiplexed stream from each primary multiplexing device, each primary multiplexed stream received by the receiving means, a packet to which a time reference reference value is assigned, and a time reference reference value Separation means that separates packets that have not been assigned, packets that have a time base reference value, and time Secondary multiplexing means for multiplexing a packet without a reference reference value and generating a secondary multiplexed stream in which one or more primary multiplexed streams are multiplexed on a packet basis, The sub-multiplexing means is characterized in that a packet to which a time base reference value related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period.
[0049]
In this digital signal multiplexing apparatus, when secondary multiplexing is performed, a packet to which a time reference reference value for each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. .
[0050]
In the digital signal multiplexing method according to the present invention, the bit stream of the digital signal is multiplexed on a packet basis in a time-division manner, and at least one time reference value indicating the output timing of the bit stream is included in the bit stream. A digital signal multiplexing method for receiving a primary multiplexed stream and generating a secondary multiplexed stream by multiplexing each received primary multiplexed stream on a packet basis in a time division manner, and receiving each primary multiplexed stream Each of the received primary multiplexed streams is separated into a packet with a time base reference value and a packet without a time base reference value, and a packet with a time base reference value. Multiplexing packets with no time base reference value attached, one or more primary multiplexed streams are When a secondary multiplexed stream multiplexed in units of packets is generated and the secondary multiplexed stream is multiplexed, a packet to which a time reference reference value for each primary multiplexed stream is assigned is set to a predetermined packet period. It is characterized by being arranged in the secondary multiplexed stream every time.
[0051]
When this digital signal multiplexing method secondary multiplexing is performed, a packet to which a time reference reference value for each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period.
[0052]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a multiplexing system to which the present invention is applied will be described as an embodiment of the present invention.
[0053]
A multiplexing system according to an embodiment of the present invention is a digital satellite broadcasting system that transmits a transport stream in which data is multiplexed for each of a plurality of programs (for example, services in which broadcast programs in television broadcasting are continuously organized). Or a recording system for recording the transport stream on a recording medium. In this multiplexing system, a plurality of primary multiplexed streams obtained by time-division multiplexing of compressed data streams (elementary streams) such as audio and video are further time-division multiplexed and used by one transponder. This is a system for generating a secondary multiplexed stream. Here, the primary multiplexed stream corresponds to the above-described television broadcast service. In the following description, it is assumed that both the primary multiplexed stream and the secondary multiplexed stream are data streams corresponding to the transport stream defined by ISO13818-1.
[0054]
First embodiment
(System configuration)
First, a multiplexing system according to a first embodiment of this invention will be described with reference to the drawings.
[0055]
FIG. 1 is a block diagram of a multiplexing system according to the first embodiment of this invention.
[0056]
As shown in FIG. 1, the multiplexing system 1 is generated by a plurality of primary multiplexers 11-1 to 11-n that generate primary multiplexed streams and the primary multiplexers 11-1 to 11-n. And a secondary multiplexer 12 that further multiplexes the primary multiplexed stream to generate a secondary multiplexed stream. Further, the secondary multiplexer 12 receives a primary multiplexed stream generated by each primary multiplexer 11-1 to 11-n and processes a plurality of receiving units 13-1 to 13- that process the stream. n, a secondary selection unit 14 that performs secondary multiplexing by selecting the primary multiplexed stream output from each of the receiving units 13-1 to 13-n, and each of the receiving units 13-1 to 13-n and the secondary And a system controller 15 that controls the selection unit 14.
[0057]
Each of the primary multiplexers 11-1 to 11-n provides a predetermined margin for the upper and lower limits of the buffer occupancy of the virtual decoder buffer, and performs the primary multiplexing of the code amount so that the virtual decoder buffer does not fail. Generate a stream. Each primary multiplexed stream is supplied to a corresponding receiving unit 13-1 to 13-n. Each of the primary multiplexers 11-1 to 11-n has an independent reference clock Cp.₁~ Cp_nIs working on. The primary multiplexed streams generated by the primary multiplexers 11-1 to 11-n are each reference clock Cp.₁~ Cp_nSynchronized with.
[0058]
Each primary multiplexed stream output from each primary multiplexer 11-1 to 11 n is input to a corresponding receiving unit 13-1 to 13-n in the secondary multiplexer 12.
[0059]
The secondary multiplexer 12 operates based on the reference clock Cr. The reference clock Cr is a reference clock Cp that is supplied to each primary multiplexer 11-1 to 11-n.₁~ Cp_nThe primary multiplexers 11-1 to 11-n and the secondary multiplexer 12 operate asynchronously.
[0060]
Receiving units 13-1 to 13-n of secondary multiplexer 12 correct PCR by separating unit 16 that separates the primary multiplexed stream into TS packets to which PCR is added and other TS packets. PCR correction unit 17, intermediate memory 18 for temporarily storing packets other than TS packets to which PCR is added, NULL packet (specified in ISO / IEC13818-1) and system information (ISO / IEC13818-1 and each broadcast) A TSP generation unit 19 that generates TS packets including (specified by the standard), and a primary selection unit 20 that selects and multiplexes the packets output from the PCR correction unit 17, the intermediate memory 18, and the TSP generation unit 19. I have.
[0061]
The separating unit 16 in each receiving unit 13 separates the input primary multiplexed stream into TS packets to which the PCR is attached and other TS packets in units of TS packets. Whether or not a PCR is assigned to the TS packet can be determined by referring to PCR_flag in adaptation_field. If the adaptation_field is provided in the TS packet and the PCR_flag in the adaptation_field is 1, the PCR is assigned to the TS packet. The separation unit 16 supplies the TS packet to which the PCR is assigned to the PCR correction unit 17 and supplies the other TS packets to the intermediate memory 18.
[0062]
The PCR correction unit 17 corrects the PCR value described in the TS packet. Specifically, when the TS packet is output as a secondary multiplexed stream based on the PCR originally calculated by the primary multiplexer 11 and the secondary multiplexing delay and secondary multiplexing jitter generated in the packet. A PCR value that is a correct value is calculated, and the PCR is rewritten to the calculated value. The PCR correction unit 17 outputs the TS packet to which the PCR is added when selected by the primary selection unit 14 in the subsequent stage.
[0063]
The intermediate memory 18 temporarily stores packets other than TS packets to which PCR is attached. The intermediate memory 18 outputs TS packets in the order received from the primary multiplexer 11 when selected by the primary selection unit 14 at the subsequent stage.
[0064]
The TSP generator 19 generates a TS packet in which a NULL packet to be inserted and system information and the like are stored in order to correct timing when performing secondary multiplexing. The TSP generation unit 19 outputs the generated TS packet when selected by the primary selection unit 14 at the subsequent stage.
[0065]
The primary selection unit 20 receives the TS packets output from the PCR correction unit 17, the intermediate memory 18, and the TSP generation unit 19 so that the packets to which the PCR is added are inserted every predetermined packet in the secondary multiplexed stream. Select appropriately and multiplex. Details of the multiplexing timing will be described later.
[0066]
Each receiving unit 13 as described above corrects the PCR value for the input primary multiplexed stream and inserts TS packets storing NULL packets and system information to process the primary multiplexed stream. And output.
[0067]
The secondary selection unit 14 of the secondary multiplexer 12 extracts the primary multiplexed stream output from each receiving unit 13 in units of TS packets, performs time division multiplexing on the extracted TS packets, and generates the secondary multiplexed stream. Is generated.
[0068]
The system controller 15 of the secondary multiplexer 12 controls the receiving units 13 and the secondary selection unit 14.
[0069]
In the multiplexing system 1 having the above-described configuration, a plurality of primary multiplexed streams are converted into one two by the TS packet selection processing performed by the secondary selection unit 14 and the primary selection unit 20 in the reception unit 13. It is multiplexed into the next multiplexed stream.
[0070]
(Multiplexing system 1)
Here, in the multiplexing system 1, the packets to which the PCR related to each primary multiplexed stream is assigned by the secondary selection unit 14 and the primary selection unit 20 are arranged in the secondary multiplexed stream every predetermined packet period. Thus, the TS packet is selected.
[0071]
For example, as shown in FIG. 2, when a secondary multiplexed stream is generated by multiplexing two primary multiplexed streams (one program A and the other program B), a PCR related to program A is added. The TS packets that are assigned are always arranged, for example, every 9 packets, and the TS packets to which the PCR related to the program B is assigned are always arranged, for example, every 3 packets.
[0072]
Hereinafter, specific description will be given of the first to fifth processing methods for performing the switching selection so that the packets to which the PCR related to each primary multiplexed stream is assigned are arranged in the secondary multiplexed stream every predetermined packet period. I will explain it.
[0073]
--First processing method--
First, the first processing method will be described.
[0074]
In the first processing method, the secondary selection unit 14 performs a multiplexing process by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set. This selection pattern is a repetitive pattern for selecting TS packets, in which the order of TS packets to be selected from each primary multiplexed stream is determined when generating a secondary multiplexed stream. The secondary selection unit 14 selects any one of the reception units 13-1 to 13-n according to the selection pattern, extracts one TS packet from the selected reception unit 13, and performs secondary multiplexing. .
[0075]
This selection pattern is determined as follows.
[0076]
First, the total number of all TS packets included in one selection pattern is set. For example, as shown in FIG. 3A, a selection pattern composed of five TS packets is set.
[0077]
Subsequently, each primary multiplexed stream is distributed to each packet position in the selection pattern. For example, when two transport streams (primary multiplexed streams) of program A and program B are secondarily multiplexed, as shown in FIG. Assign to program A (first, third and fifth packets in selection pattern) and two packets to program B (second and fourth packets in selection pattern).
[0078]
Subsequently, the bit rate of each primary multiplexed stream is determined from the bit rate of the secondary multiplexed stream and the number of TS packets distributed to each primary multiplexed stream. For example, if the bit rate of the secondary multiplexed stream is 1 Mbps, program A is assigned to 600 kbps and program B is assigned to 400 kbps as shown in FIG. These are called the assigned bit rates of each primary multiplexer.
[0079]
As described above, the selection pattern and the bit rate of the primary multiplexed stream are determined. In addition, when the bit rate of the primary multiplexed stream is determined in advance, the selection pattern may be determined in reverse from the ratio of the bit rate of each primary multiplexed stream.
[0080]
The secondary selection unit 14 sequentially selects the primary multiplexed stream according to the set selection pattern and performs secondary multiplexing.
[0081]
As described above, the secondary multiplexing jitter can be set to a known value by performing the secondary multiplexing according to the preset selection pattern. Therefore, by generating a primary multiplexed stream with a margin corresponding to the secondary multiplexing jitter determined according to this selection pattern, the decoding side does not fail even after secondary multiplexing.
[0082]
Further, in this first processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets to which PCR is attached are arranged for every predetermined number of packets. The generation interval of TS packets to which PCR is assigned is an interval corresponding to the number of packets assigned to the selection pattern.
[0083]
For example, when a selection pattern including five TS packets is set, three TS packets are assigned to program A, and two TS packets are assigned to program B, FIG. ), The primary multiplexer 11 that generates the program A outputs a TS packet to which PCR is added every 3 packets, and the primary multiplexer 11 that generates the program B applies PCR to every 2 packets Output TS packets.
[0084]
Thus, when each primary multiplexer 11 generates a secondary multiplexed stream by generating a primary multiplexed stream in which TS packets to which PCR is attached are generated for each allocated number of packets. Packets to which PCR related to each primary multiplexed stream is assigned are arranged in the secondary multiplexed stream every predetermined packet period. For example, as shown in FIG. 4B, it is possible to generate a secondary multiplexed stream in which the PCR related to the program A and the PCR related to the program B are arranged every 5 packets.
[0085]
By the way, the multiplexing system 1 is an asynchronous system in which the reference clocks of the primary multiplexer 11 and the secondary multiplexer 12 are not synchronized.
[0086]
That is, in the case of a synchronous system in which the reference clock Cp of the primary multiplexer 11 and the reference clock Cr of the secondary multiplexer 12 are synchronized, secondary multiplexing jitter is obtained by performing secondary multiplexing according to the selected pattern. Does not exceed a certain amount, and the secondary multiplexing jitter does not increase. For example, as shown in FIG. 5A, in the case of a synchronous system, the maximum value of the secondary multiplexing jitter D (i) is known in the selected pattern and does not increase beyond the maximum value.
[0087]
However, in the case of the multiplexing system 1 of the present embodiment in which the reference clocks of the primary multiplexer 11 and the secondary multiplexer 12 are asynchronous, even if secondary multiplexing is performed according to the selected pattern, the difference between the reference clocks The resulting errors accumulate and secondary multiplexing jitter increases. For example, as shown in FIG. 5B, if the reference clock Cr of the secondary multiplexer 12 is larger than the reference clock Cp of the primary multiplexer 11, the multiplexing timing of each packet is advanced. As multiplexing progresses, secondary multiplexing jitter increases. In the case of performing the secondary multiplexing, a secondary multiplexing delay that actually occurs fixedly in each packet also occurs. However, in order to explain the increase of the secondary multiplexing jitter in an easy-to-understand manner, FIG. It is omitted.
[0088]
When the secondary multiplexing jitter increases in this way, the difference between the PCR value and the actual reception timing increases, and the decoder processing fails.
[0089]
Therefore, in this first processing method, when the output timing of the secondary multiplexed stream advances temporally with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexing jitter exceeds a certain threshold value. In addition, dummy data (NULL packet) is forcibly inserted to reduce secondary multiplexing jitter.
[0090]
For example, as shown in FIG. 6, since the secondary multiplexing jitter D (2) of the TS packet (b2) of the program B is equal to or less than the threshold D (th), no special correction processing is performed. . On the other hand, the secondary multiplexing jitter D (4) of the TS packet (b4) is larger than the threshold value D (th). For this reason, in the original selection pattern, dummy data (NULL packet) is inserted into the region of the secondary multiplexed stream that was scheduled to be secondary multiplexed of the TS packet (b5).
[0091]
Further, in order to place the TS packet to which the PCR is attached in the secondary multiplexed stream at every predetermined packet period, the packet to which the PCR is subsequently attached is placed at a predetermined position in the selection pattern. Thus, the selection order of TS packets in the primary multiplexed stream is switched. At the same time, the PCR value generated by changing the TS packet selection order is corrected based on the PCR value originally attached to the primary multiplexed stream.
[0092]
For example, as shown in FIG. 6, since the PCR is added to the TS packet (b6) after the NULL packet is inserted, this TS packet (b6) is arranged at the second packet position of the selection pattern, A TS packet (b5) to which no PCR is attached is arranged at the fourth packet position of the selection pattern. Then, the PCR value assigned to the TS packet (b6) is corrected to the correct PCR value when the second multiplexed output is made with reference to the value originally attached. Thereafter, selection switching is performed so that the TS packet (b8), TS packet (b10), TS packet (b12)... To which the PCR is attached is always placed at the second packet position in the selection pattern. The PCR value is corrected.
[0093]
As described above, in the first processing method, dummy data (NULL packet) is inserted into the secondary multiplexed stream to correct the increase in secondary multiplexing jitter due to the asynchronous system. Furthermore, in the first processing method, a shift in the position to which the PCR is added due to the insertion of dummy data (NULL packet) is corrected by switching the selection order of the TS packets and correcting the PCR. By performing such processing, in the first processing method, switching is performed so that TS packets to which PCR related to each primary multiplexed stream is assigned are arranged in the secondary multiplexed stream at predetermined packet periods. You can make a choice.
[0094]
In the first processing method, the secondary multiplexing jitter is corrected on the premise that the output timing of the secondary multiplexed stream advances with respect to the reception timing of the primary multiplexed stream. . Therefore, if it is compensated that the reference clock Cr of the secondary multiplexer 12 is earlier than the reference clock Cp of the primary multiplexer 11, the secondary multiplexing process can be reliably performed by this first processing method. Can do.
[0095]
In order to compensate that the reference clock Cr of the secondary multiplexer 12 becomes earlier than the reference clock Cp of the primary multiplexer 11, for example, the maximum value of the rating of the reference clock of the primary multiplexer is set to CpMAX, If the minimum value of the reference clock of the secondary multiplexer is CrMIX and the bit rate assigned to the primary multiplexer based on the selection pattern is P, the bit rate of the primary multiplexed stream output from the primary multiplexer Should be set as follows.
[0096]
(CrMIN / CpMAX) x P
Further, the dummy data for adjusting the secondary multiplexing jitter may be inserted not only a NULL packet but also a TS packet in which system information is described.
[0097]
--Second processing method--
Next, the second processing method will be described.
[0098]
In the second processing method, the secondary selection unit 14 performs a multiplexing process by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set. This selection pattern is determined in the same manner as in the first processing method described above.
[0099]
Further, in the second processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets to which PCR is assigned are arranged at regular time intervals. The time interval of the TS packet to which the PCR is assigned is a time interval corresponding to the cycle of the selection pattern.
[0100]
For example, if the bit rate of the secondary multiplexed stream is 1 Mbps and a selection pattern composed of five TS packets is set, the cycle of the selection pattern is (T = 5 × 8 × 188 × 10).^-6) At this time, as shown in FIG. 7A, the primary multiplexer 11 outputs a TS packet to which PCR is added every period T. Each primary multiplexer 11 may freely decimate other TS packets as long as it outputs TS packets into which PCR has been inserted at least every period T, and may insert dummy data (NULL packets). .
[0101]
In this way, when each primary multiplexer 11 generates a secondary multiplexed stream by generating a primary multiplexed stream in which TS packets to which PCR is attached are generated every period T of the selection pattern. Packets to which PCR related to each primary multiplexed stream is assigned are arranged in the secondary multiplexed stream every predetermined packet period. For example, as shown in FIG. 7B, it is possible to generate a secondary multiplexed stream in which the PCR related to the program A and the PCR related to the program B are arranged every 5 packets. If some packets of the primary multiplexed stream are thinned out or replaced with dummy packets, there will be no data at the specified packet position in the secondary multiplexed stream There is. In that case, a null packet or a TS packet in which system information is described is inserted at the empty packet position.
[0102]
Further, in the second processing method, as in the first processing method, the output timing of the secondary multiplexed stream is temporally advanced with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexing is performed. When the jitter exceeds a certain threshold value, dummy data (NULL packet) is forcibly inserted to reduce secondary multiplexing jitter.
[0103]
Further, in order to place the packets to which the PCR is attached in the secondary multiplexed stream at predetermined packet periods, the packets to which the PCR is subsequently attached are placed at predetermined positions in the selection pattern. Next, the selection order of TS packets in the primary multiplexed stream is switched. At the same time, the PCR value generated by changing the TS packet selection order is corrected based on the PCR value originally attached to the primary multiplexed stream.
[0104]
As described above, in the second processing method, dummy data (NULL packet) is inserted to correct an increase in secondary multiplexing jitter due to the asynchronous system. Furthermore, in the second processing method, the shift of the PCR application position accompanying the insertion of dummy data (NULL packet) is corrected by switching the selection order of TS packets and correcting the PCR. By performing such processing, in the second processing method, switching selection is performed so that a packet to which a PCR related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. Can do.
[0105]
Also in the second processing method, similarly to the first processing method, the secondary multiplexed stream output timing is temporally advanced with respect to the reception timing of the primary multiplexed stream. Multiplexed jitter is corrected. Therefore, this second processing method also compensates for the reference clock Cr of the secondary multiplexer 12 being earlier than the reference clock Cp of the primary multiplexer 11 as shown in the following equation.
[0106]
(CrMIN / CpMAX) x P
--Third processing method--
Next, the third processing method will be described.
[0107]
In the third processing method, the secondary selection unit 14 performs a multiplexing process by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set. This selection pattern is determined in the same manner as in the first processing method described above.
[0108]
Further, in this third processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets to which PCR is attached are arranged for every fixed number of packets. The generation interval of TS packets to which PCR is assigned is an interval corresponding to the number of packets assigned to the selection pattern. The generation interval of TS packets to which this PCR is attached is determined in the same manner as in the first processing method described above.
[0109]
Further, in the third processing method, when the output timing of the secondary multiplexed stream is delayed with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexing jitter exceeds a certain threshold value. The dummy data (NULL packet) is forcibly deleted from the primary multiplexed stream to reduce secondary multiplexing jitter. Note that the primary multiplexer 11 generates a primary multiplexed stream in which dummy data (NULL packets) are inserted at appropriate intervals in advance so that the dummy data can be forcibly deleted.
[0110]
For example, as shown in FIG. 8, since the secondary multiplexing jitter D (2) of the TS packet (b2) of the program B is equal to or less than the threshold value D (th), no special correction processing is performed. . On the other hand, the secondary multiplexing jitter D (4) of the TS packet (b4) is larger than the threshold value D (th). Therefore, the NULL packet (b5 in this case) next to the TS packet (b4) is deleted.
[0111]
Further, in order to place the packets to which the PCR is attached in the secondary multiplexed stream at predetermined packet periods, the packets to which the PCR is subsequently attached are placed at predetermined positions in the selection pattern. Next, the selection order of TS packets in the primary multiplexed stream is switched. At the same time, the PCR value generated by changing the TS packet selection order is corrected based on the PCR value originally attached to the primary multiplexed stream.
[0112]
Here, as shown in FIG. 8, since the PCR is added to the TS packet (b6) after the NULL packet is deleted, the selection order of the TS packet (b6) and the TS packet (b7) is changed, The TS packet (b6) is arranged at the second packet position in the selection pattern, and the TS packet (b7) to which no PCR is attached is arranged at the fourth packet position in the selection pattern. Then, the PCR value assigned to the TS packet (b6) is corrected to the correct PCR value when the second multiplexed output is made with reference to the value originally attached. Thereafter, selection switching is performed so that the TS packet (b8), TS packet (b10), TS packet (b12)... To which the PCR is attached is always placed at the second packet position in the selection pattern. The PCR value is corrected.
[0113]
As described above, in the third processing method, the increase in the secondary multiplexing jitter due to the asynchronous system is corrected by deleting the dummy data (NULL packet) from the primary multiplexed stream. Furthermore, in the third processing method, the shift in the PCR application position accompanying deletion of dummy data (NULL packet) is corrected by switching the selection order of TS packets and correcting the PCR. By performing such processing, in the third processing method, switching selection is performed so that a packet to which PCR related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. Can do.
[0114]
In the third processing method, the secondary multiplexing jitter is corrected on the assumption that the output timing of the secondary multiplexed stream is delayed with respect to the reception timing of the primary multiplexed stream. . Therefore, if it is compensated that the reference clock Cr of the secondary multiplexer 12 is slower than the reference clock Cp of the primary multiplexer 11, the secondary multiplexing process can be reliably performed by the third processing method. it can.
[0115]
In order to compensate that the reference clock Cr of the secondary multiplexer 12 becomes slower than the reference clock Cp of the primary multiplexer 11, for example, the maximum value of the rating of the reference clock of the primary multiplexer is set to CpMAX, If the minimum value of the reference clock of the secondary multiplexer is CrMIN and the bit rate assigned to the primary multiplexer based on the selection pattern is P, the bit rate of the primary multiplexed stream output from the primary multiplexer Should be set as follows.
[0116]
(CpMAX / CrMIN) × P
--Fourth processing method--
Next, the fourth processing method will be described.
[0117]
In the fourth processing method, the secondary selection unit 14 determines the selection pattern in which the switching order for selecting the primary multiplexed stream is determined, and performs the multiplexing process. This selection pattern is determined in the same manner as in the first processing method described above.
[0118]
Further, in the fourth processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets provided with PCR are arranged at regular time intervals. The time interval of the TS packet to which the PCR is assigned is a time interval corresponding to the cycle of the selection pattern. This time interval is determined in the same manner as in the second processing method described above.
[0119]
Further, in the fourth processing method, as in the third processing method, the output timing of the secondary multiplexed stream is delayed with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexing is performed. When the jitter exceeds a certain threshold, dummy data (NULL packet) is forcibly deleted from the primary multiplexed stream to reduce the secondary multiplexed jitter.
[0120]
Further, in order to place the packets to which the PCR is attached in the secondary multiplexed stream at predetermined packet periods, the packets to which the PCR is subsequently attached are placed at predetermined positions in the selection pattern. Next, the selection order of TS packets in the primary multiplexed stream is switched. At the same time, the PCR value generated by changing the TS packet selection order is corrected based on the PCR value originally attached to the primary multiplexed stream.
[0121]
As described above, in the fourth processing method, the increase in the secondary multiplexing jitter due to the asynchronous system is corrected by deleting the dummy data (NULL packet). Furthermore, in the fourth processing method, a shift in the position to which the PCR is added due to deletion of dummy data (NULL packet) is corrected by switching the selection order of TS packets and correcting the PCR. By performing such processing, in the fourth processing method, switching selection is performed so that a packet to which PCR related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. Can do.
[0122]
Also in the fourth processing method, similarly to the third processing method, it is assumed that the output timing of the secondary multiplexed stream is delayed with respect to the reception timing of the primary multiplexed stream. Multiplexed jitter is corrected. Therefore, as shown in the following equation, it is compensated that the reference clock Cr of the secondary multiplexer 12 becomes earlier than the reference clock Cp of the primary multiplexer 11.
[0123]
(CpMIN / CrMIN) × P
--Fifth processing method--
Next, the fifth processing method will be described.
[0124]
In the fifth processing method, the secondary selection unit 14 performs a multiplexing process by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set. This selection pattern is determined in the same manner as in the first processing method described above.
[0125]
Further, in the fifth processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets to which PCR is attached are arranged for every fixed number of packets. The generation interval of TS packets to which PCR is assigned is an interval corresponding to the number of packets assigned to the selection pattern. The generation interval of TS packets to which this PCR is attached is determined in the same manner as in the first processing method described above. In the fifth processing method, as in the second processing method, the primary multiplexed stream in which the TS packets to which the PCR is attached is arranged at each time interval is output from each primary multiplexer 11. It may be.
[0126]
Further, in the fifth processing method, when the output timing of the secondary multiplexed stream advances temporally with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexing jitter exceeds a certain threshold value. In addition, dummy data (NULL packet) is forcibly inserted to reduce secondary multiplexing jitter. At the same time, in the fifth processing method, the output timing of the secondary multiplexed stream is delayed with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexing jitter exceeds a certain threshold. When this happens, dummy data (NULL packet) is forcibly deleted from the primary multiplexed stream to reduce secondary multiplexing jitter.
[0127]
That is, in the fifth processing method, both the deletion of the dummy data from the primary multiplexed stream and the insertion of the dummy data into the secondary multiplexed data are performed to reduce the secondary multiplexing jitter.
[0128]
Further, in order to place the packets to which the PCR is attached in the secondary multiplexed stream at predetermined packet periods, the packets to which the PCR is subsequently attached are placed at predetermined positions in the selection pattern. Next, the selection order of TS packets in the primary multiplexed stream is switched. At the same time, the PCR value generated by changing the TS packet selection order is corrected based on the PCR value originally attached to the primary multiplexed stream.
[0129]
As described above, in the fifth processing method, dummy data (NULL packet) is inserted and deleted to correct an increase in secondary multiplexing jitter due to the asynchronous system. Furthermore, in the fifth processing method, a shift in the PCR attachment position accompanying insertion and deletion of a dummy packet (NULL packet) is corrected by switching the selection order of TS packets and correcting the PCR. By performing such processing, in the fifth processing method, switching selection is performed so that a packet to which PCR related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. Can do.
[0130]
In addition, in the fifth processing method, since the output timing of the secondary multiplexed stream does not presuppose that it is temporally advanced or delayed with respect to the reception timing of the primary multiplexed stream, Processing can be performed without compensating the reference clocks of the multiplexer 11 and the secondary multiplexer 12.
[0131]
Second embodiment
Next, a multiplexing system according to a second embodiment of this invention will be described with reference to the drawings. In the description of the multiplexing system of the second embodiment, the same components as those of the multiplexing system 1 of the first embodiment described above are denoted by the same reference numerals in the drawings, and the detailed description thereof will be omitted. Description is omitted.
[0132]
FIG. 9 is a block diagram of a multiplexing system according to the second embodiment of this invention.
[0133]
As shown in FIG. 9, the multiplexing system 30 is generated by a plurality of primary multiplexers 11-1 to 11-n that generate primary multiplexed streams and the primary multiplexers 11-1 to 11-n. And a secondary multiplexer 32 for further multiplexing the primary multiplexed stream to generate a secondary multiplexed stream. The secondary multiplexer 32 also receives a primary multiplexed stream generated by each primary multiplexer 11-1 to 11-n and processes a plurality of receiving units 33-1 to 33-33 that process the stream. -n, a secondary selection unit 34 that selects and multiplexes the primary multiplexed stream output from each of the reception units 33-1 to 33-n, and each of the reception units 33-1 to 33-n and 2 And a system controller 15 that controls the next selection unit 34.
[0134]
Each primary multiplexed stream output from each primary multiplexer 11-1 to 11 n is input to a corresponding receiving unit 33-1 to 33-n in the secondary multiplexer 32.
[0135]
The secondary multiplexer 32 operates based on the reference clock Cr. The reference clock Cr is a reference clock Cp that is supplied to each primary multiplexer 11-1 to 11-n.₁~ Cp_nThe primary multiplexers 11-1 to 11-n and the secondary multiplexer 32 operate asynchronously.
[0136]
Each receiving unit 33-1 to 33-n of the secondary multiplexer 32 includes a separating unit 36 that separates the primary multiplexed stream into TS packets to which PCR is added and other TS packets, and a primary multiplexed stream. A PCR deleting unit 37 for deleting the PCR attached to the PCR, a PCR generating unit 38 for newly generating a PCR, an intermediate memory 39 for temporarily storing packets other than the TS packet to which the PCR is added, and a NULL packet. (Specified in ISO / IEC13818-1) and system information (specified by ISO / IEC13818-1 and each broadcast standard) TSP generation unit 40 that generates a TS packet, PCR deletion unit 37, PCR generation unit 38, intermediate A memory 39 and a primary selection unit 41 that selects and multiplexes each packet output from the TSP generation unit 40 are provided.
[0137]
The separating unit 36 in each receiving unit 33 separates the input primary multiplexed stream into TS packets to which the PCR is attached and other TS packets in units of TS packets. Whether or not a PCR is assigned to the TS packet can be determined by referring to PCR_flag in adaptation_field. The separation unit 36 supplies the TS packet to which the PCR is assigned to the PCR deletion unit 37 and the PCR generation unit 38, and supplies the other TS packets to the intermediate memory 39.
[0138]
The PCR deletion unit 37 performs processing for replacing the PCR assigned to the original primary multiplexed stream with dummy data. Specifically, as shown in FIG. 10, when the PCR is described in the TS packet, “1” is described as the value of PCR_Flag described in the adaptation_field, and further, the PCR is included in the subsequent 6 bytes. Are encoded. The PCR deleting unit 37 replaces the value of PCR_Flag from 1 to 0, deletes the subsequent 6-byte PCR, and inserts stuffing_byte at the end of the adaptation_field. By performing such processing, the PCR can be deleted without changing the adaptation_field and the byte length of the TS packet.
[0139]
The PCR generation unit 38 generates a TS packet to which a new PCR to be inserted when secondary multiplexing is performed. Specifically, based on the PCR originally calculated by the primary multiplexer 11, a PCR value that is correct when the TS packet is output as a secondary multiplexed stream is calculated. A TS packet to which is added is generated. The PCR correcting unit 38 outputs the TS packet to which the PCR is added when selected by the primary selection unit 41 in the subsequent stage.
[0140]
The intermediate memory 39 temporarily stores packets other than TS packets to which PCR is attached. The intermediate memory 39 outputs TS packets in the order received from the primary multiplexer 11 when selected by the primary selection unit 41 in the subsequent stage.
[0141]
The TSP generator 40 generates a TS packet in which a NULL packet to be inserted and system information or the like are stored in order to correct timing when performing secondary multiplexing. The TSP generation unit 40 outputs the generated TS packet when selected by the primary selection unit 41 in the subsequent stage.
[0142]
The primary selection unit 41 includes a PCR deletion unit 37, a PCR generation unit 38, an intermediate memory 39, and a TSP generation unit 40 so that TS packets to which PCR is added are inserted every fixed packet in the secondary multiplexed stream. The output TS packet is appropriately selected and multiplexed. Details of the multiplexing timing will be described later.
[0143]
Each receiving unit 33 as described above corrects the PCR value for the input primary multiplexed stream and inserts TS packets storing NULL packets and system information to process the primary multiplexed stream. And output.
[0144]
The secondary selection unit 34 of the secondary multiplexer 32 extracts the primary multiplexed stream output from each receiving unit 33 in units of TS packets, time-division multiplexes the extracted TS packets, and outputs the secondary multiplexed stream Is generated.
[0145]
The system controller 35 of the secondary multiplexer 32 controls the receiving units 33 and the secondary selection unit 34.
[0146]
In the multiplexing system 30 having the above-described configuration, a plurality of primary multiplexed streams are converted into one two by the TS packet selection processing performed by the secondary selection unit 34 and the primary selection unit 41 in the reception unit 33. It is multiplexed into the next multiplexed stream.
[0147]
(Multiplexing system of multiplexing system 30)
In the multiplexing system 30, the secondary selection unit 34 and the primary selection unit 41 are arranged so that the packets to which the PCR related to each primary multiplexed stream is assigned are arranged in the secondary multiplexed stream at predetermined packet periods. TS packets are selected.
[0148]
A method for performing switching selection so that a packet to which a PCR related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period is the same as that of the first embodiment. This is the same as the first to fifth processing methods.
[0149]
However, since the PCR packet to which the PCR is added is newly generated by the PCR generation unit 38, it is selected from the output of the PCR generation unit 38. The bit rate P that can be assigned to each primary multiplexer is calculated in consideration of the number of newly generated TS packets (TS packets to which PCR is added). For example, as shown in FIG. 3, the bit rate of the secondary multiplexed stream is 1 Mbps, and a selection pattern composed of 5 TS packets is set. Assume that two TS packets are allocated to B. Then, it is assumed that TS packets to which one PCR is assigned for both the program A and the program B are arranged in each selection pattern. At that time, the bit rate of program A can be assigned to 4 kbps, and the bit rate of program B can be assigned to 2 kbps.
[0150]
As described above, in the multiplexing system 1 according to the first embodiment of the present invention and the multiplexing system 30 according to the second embodiment, when the secondary multiplexing is performed, the PCR for each primary multiplexed stream is performed. The given packet is arranged in the secondary multiplexed stream at every predetermined packet period.
[0151]
As a result, the multiplexing systems 1 and 30 can generate the primary multiplexed stream and the secondary multiplexed stream based on the asynchronous reference clock, reduce the secondary multiplexing jitter, It is possible to generate a secondary multiplexed stream that does not break the processing on the decoding side. Furthermore, in the multiplexing systems 1 and 30, the time base reference value can be arranged at a fixed position in the secondary multiplexed stream, and this is a receiving method for receiving only a part of TS packets in the secondary multiplexed stream. However, the system clock can be reliably restored on the receiving side.
[0152]
For example, in a broadcasting system that implements partial reception in which only a part of a band signal in one broadcasting frequency channel can be extracted and received, such as in digital broadcasting employing an OFDM modulation system, Only a part of the TS packets may be decoded. Even in the case of such partial reception, in the present invention, the PCR can be surely included in the extracted part of TS packets, and the system clock can be reliably restored on the receiving side.
[0153]
In describing the switching process of the multiplexing system according to the embodiment of the present invention, a process for arranging a packet to which a PCR is attached in a secondary multiplexed stream every predetermined packet period using a selection pattern. An example is shown. However, in the present invention, the switching process may be performed without setting such a selection pattern. For example, TS packets may be selected in order from the primary multiplexed stream in which the number of packets stored in the intermediate memories 18 and 39 is large, and the secondary multiplexing processing may be performed, or the TS packets that are received earlier are selected in order. Then, the secondary multiplexing process may be performed. Of course, even in such a case, the switching process is performed so that the packet to which the PCR related to each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period.
[0154]
In addition, the secondary multiplexing jitter is shown in the drawing as being detected at the start timing of the TS packet, but if the detection position in the TS packet is fixed, not only the start of the TS packet, Jitter may be detected at a data position in any TS packet.
[0155]
【The invention's effect】
In the digital signal multiplexing apparatus and method according to the present invention, when secondary multiplexing is performed, a packet to which a time base reference value relating to each primary multiplexed stream is given is secondary multiplexed every predetermined packet period. Place in the stream.
[0156]
Thus, in the digital signal multiplexing apparatus and method according to the present invention, the primary multiplexed stream and the secondary multiplexed stream can be generated based on the asynchronous reference clock, and the secondary multiplexing jitter is reduced. Thus, it is possible to generate a secondary multiplexed stream that does not break down the processing on the receiving side or the decoding side. Further, in this digital signal multiplexing apparatus, a time base reference value can be arranged at a fixed position in the secondary multiplexed stream, and a reception method for receiving only a part of the packets in the secondary multiplexed stream is provided. Also, the system clock can be reliably restored on the receiving side.
[0157]
For example, in a broadcast system that realizes partial reception in which only a part of a band signal in one broadcast frequency channel can be extracted and received, such as in a digital broadcast employing an OFDM (Orthogonal Frequency Division Multiplexing) modulation system, 1 In some cases, only a part of TS packets in one transport stream is decoded. Even in the case of such partial reception, in the present invention, the PCR can be surely included in the extracted part of TS packets, and the system clock can be reliably restored on the receiving side.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of a multiplexing system according to a first embodiment of this invention.
FIG. 2 is a diagram for explaining an example in which a packet to which a PCR related to each primary multiplexed stream is assigned is arranged in a secondary multiplexed stream every predetermined packet period;
FIG. 3 is a diagram for explaining a selection pattern setting method;
FIG. 4 is a diagram for explaining an arrangement example of packets to which PCR is added.
FIG. 5 is a diagram for explaining secondary multiplexing jitter;
FIG. 6 is a diagram for explaining an example of inserting a NULL packet into a secondary multiplexed stream;
FIG. 7 is a diagram for explaining a primary multiplexed stream in which TS packets to which PCR is added are arranged at regular time intervals;
FIG. 8 is a diagram for explaining an example of deleting a NULL packet from a primary multiplexed stream;
FIG. 9 is a block configuration diagram of a multiplexing system according to a second embodiment of this invention.
FIG. 10 is a diagram for explaining a PCR rewriting process;
FIG. 11 is a block configuration diagram of a broadcasting system that transmits a transport stream used for digital broadcasting or the like.
FIG. 12 is a diagram illustrating a data structure of a primary multiplexed stream and a secondary multiplexed stream that are transport streams defined by ISO 33818-1.
FIG. 13 is a diagram illustrating a data structure of a TS packet defined by ISO 33818-1.
FIG. 14 is a diagram for explaining a decoder model of the broadcasting system.
FIG. 15 is a diagram for explaining a secondary multiplexing method proposed in Japanese Patent Laid-Open No. 11-235083.
FIG. 16 is a diagram for explaining secondary multiplexing jitter generated when multiplexing is performed by the secondary multiplexing method proposed in Japanese Patent Laid-Open No. 11-235083.
FIG. 17 is a diagram for explaining secondary multiplexing jitter generated when multiplexing is performed by the secondary multiplexing method proposed in Japanese Patent Laid-Open No. 11-235082;
FIG. 18 is a diagram for explaining partial reception employed in ISDB-T.
[Explanation of symbols]
1,30 Multiplexing System, 11 Primary Multiplexer, 12, 32 Secondary Multiplexer, 13, 33 Receiver, 14, 34 Secondary Selector, 15, 35 System Controller, 16, 36 Separation Unit, 17 PCR Correction unit, 18, 39 Intermediate memory, 19, 40 TSP generation unit, 20, 41 Primary selection unit, 37 PCR deletion unit, 38 PCR generation unit

Claims (21)

A bit stream of a digital signal is multiplexed on a packet basis in a time division manner, and at least one primary multiplexed stream including a time base reference value indicating the output timing of the bit stream is included in the bit stream. In a digital signal multiplexing device that receives from a multiplexing device and multiplexes each received primary multiplexed stream in a time division manner in units of packets to generate a secondary multiplexed stream,
Receiving means for receiving each primary multiplexed stream from each primary multiplexing device;
Separating means for separating each of the primary multiplexed stream received by said receiving means, a packet time reference value is applied, the packet has not been granted a time standard reference value,
A packet the time reference value is assigned, and a packet in which the time reference value is not given by multiplexing, multiplexed secondary multiplexing one or more of the primary multiplexed stream in packets Secondary multiplexing means for generating a stream,
The above-mentioned secondary multiplexing means arranges a packet to which a time base reference value for each primary multiplexed stream is assigned in the secondary multiplexed stream every predetermined packet period. apparatus. Time base reference value correction means for correcting the time base reference value included in each primary multiplexed stream to a value synchronized with the output timing of the packet when multiplexed as a secondary multiplexed stream. 2. The digital signal multiplexing apparatus according to claim 1, wherein 3. The digital signal according to claim 2, wherein the demultiplexing unit receives, from each primary multiplexing device, a primary multiplexed stream in which packets to which a time base reference value is assigned are arranged for each predetermined number of packets. Multiplexer. 3. The digital signal according to claim 2, wherein the demultiplexing unit receives, from each primary multiplexing device, a primary multiplexed stream in which packets to which a time base reference value is assigned are arranged at predetermined output time intervals. Signal multiplexer. A reference clock for operating the digital signal multiplexing apparatus main body is a reference clock and asynchronous for operating the primary multiplexer,
When the time base reference value corrected by the time base reference value correcting means is a predetermined time or more earlier than the time base reference value added to the primary multiplexed stream, the secondary multiplexing means The digital signal multiplexing apparatus according to claim 2, wherein the data is included in the secondary multiplexed stream. Bit rate of the outputted secondary multiplexed stream, claims, characterized in that it is also higher control than the sum of the assigned the bit rate for each of the primary multiplexed stream for secondary multiplexed output 5. The digital signal multiplexing device according to 5. The receiving means has a minimum reference clock rating for operating the digital signal multiplexing device main body as CrMIN, a maximum reference clock rating for operating the primary multiplexing device as CpMAX, and each primary multiplexing. If the bit rate assigned to the stream is P, the bit rate is
(CrMIN / CpMAX) x P
The digital signal multiplexing apparatus according to claim 6, wherein each primary multiplexed stream set to 1 is received from each primary multiplexing apparatus. A reference clock for operating the digital signal multiplexing apparatus main body is a reference clock and asynchronous for operating the primary multiplexer,
If the time base reference value corrected by the time base reference value correction means is delayed by a certain time or more than the time base reference value added to the primary multiplexed stream, the secondary multiplexing means 3. The digital signal multiplexing apparatus according to claim 2, wherein dummy data included in the multiplexed stream is deleted. The bit rate of the output secondary multiplexed stream is controlled to be lower than the sum of the bit rates assigned to each primary multiplexed stream for the secondary multiplexed output. The digital signal multiplexing apparatus described. The receiving means has a minimum reference clock rating for operating the digital signal multiplexing device main body as CrMIN, a maximum reference clock rating for operating the primary multiplexing device as CpMAX, and each primary multiplexing. If the bit rate assigned to the stream is P, the bit rate is
(CpMAX / CrMIN) × P
The digital signal multiplexing apparatus according to claim 9, wherein each primary multiplexed stream set to 1 is received from each primary multiplexing apparatus. 9. The digital signal multiplexing apparatus according to claim 8, wherein the receiving means receives a primary multiplexed stream in which dummy data is multiplexed from each primary multiplexing apparatus. The digital signal multiplexing apparatus according to claim 2, wherein the primary multiplexed stream and the secondary multiplexed stream are transport streams defined by ISO / IEC13818-1. The digital signal multiplexing apparatus according to claim 12, wherein the time reference value is a PCR (Program Clock Reference) defined in ISO / IEC13818-1. The digital signal multiplexing apparatus according to claim 11 , wherein the dummy data is a NULL transport stream packet defined in ISO / IEC13818-1. Time base reference value removing means for removing the time base reference value from the packet to which the separated time base reference value is assigned;
A time base reference value for obtaining a time base reference value corresponding to the secondary multiplexed stream based on the time base reference value included in the primary multiplexed stream and generating a new packet with the obtained time base reference value. The digital signal multiplexing apparatus according to claim 1, further comprising a generation unit. 16. The digital signal multiplexing apparatus according to claim 15, wherein the time base reference value removing unit replaces the time base reference value of the packet to which the separated time base reference value is assigned with dummy data. A reference clock for operating the digital signal multiplexing apparatus main body is a reference clock and asynchronous for operating the primary multiplexer,
Bit rate of the outputted secondary multiplexed stream, the sum of the allocated a bit rate for each of the primary multiplexed stream for secondary multiplexed output, new packet corresponds to reference value may have been granted time The digital signal multiplexing apparatus according to claim 15, wherein a bit rate is obtained by adding a bit rate of minutes. The digital signal multiplexing apparatus according to claim 15, wherein the primary multiplexed stream and the secondary multiplexed stream are transport streams defined by ISO / IEC13818-1. 19. The digital signal multiplexing apparatus according to claim 18, wherein the time base reference value is a PCR (Program Clock Reference) defined in ISO / IEC13818-1. The time base reference value removing means replaces PCR_Flag of the packet to which the PCR is attached with 0, inserts Stuffing_byte having a data length equal to the PCR, and removes the time base reference value from the primary multiplexed stream. 20. The digital signal multiplexing apparatus according to claim 19, wherein: Received and received one or more primary multiplexed streams in which the bit stream of the digital signal is multiplexed on a packet basis in a time-division manner and the bit stream includes a time base reference value indicating the output timing of the bit stream In a digital signal multiplexing method for generating a secondary multiplexed stream by multiplexing each primary multiplexed stream in a time division manner in units of packets,
Receiving each primary multiplexed stream;
Received respective primary multiplexed stream, a packet in which the time reference value is applied, is separated into the packet the time reference value has not been granted,
A packet the time reference value is assigned, and a packet in which the time reference value is not given by multiplexing, multiplexed secondary multiplexing one or more of the primary multiplexed stream in packets Create a stream,
When multiplexing the secondary multiplexed stream, the packets to which the time base reference values for the respective primary multiplexed streams are assigned are arranged in the secondary multiplexed stream every predetermined packet period. Digital signal multiplexing method.

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