JP2002208904A - Digital signal multiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a secondary multiplexing to be carried out so as to surely contain PCR even when partial receiving is carried out in an ISDB-T. SOLUTION: A plurality of transport streams are subjected to asymmetrical secondary multiplexing processing to generate transport streams containing a plurality of programs. At this point, a selection pattern which selects the program by the TS packet is determined, and it is so specified as to enable a secondary multiplexing jitter not to exceed a certain amount. Furthermore, clock errors generated in an asynchronous system are accumulated, and when the secondary multiplexing jitter exceeds a threshold value, a null packet is inserted so as to remove errors. Furthermore, PCR is corrected, and also the insertion position of PCR is controlled so as to insert the PCR into a selection pattern at a prescribed position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for multiplexing digital signals such as video and audio to generate a primary multiplexed stream including a program such as a television program or a radio program. And a digital signal multiplexing apparatus and method for generating a secondary multiplexed stream obtained by further quadrature multiplexing.

[0002]

2. Description of the Related Art A transport stream for multiplexing and transmitting one or more programs (for example, a service in which broadcast programs in television broadcasting are continuously arranged) into one multiplexed stream is an ISO / IEC13818. -1 and a multiplexing system for generating this transport stream has been conventionally known.

FIG. 11 shows an example of a broadcast system configuration for transmitting a transport stream using digital broadcasting or the like.

The transmitting apparatus 100 is supplied with baseband video data and audio data corresponding to a plurality of programs or data (not shown) from a server or a video camera. The video data and audio data are stored in a video encoder 111 corresponding to each program.
(111-1 to 111-n) and a compressed data stream (elementary stream) corresponding to, for example, MPEG-2 (ISO / IEC11172, ISO13818) or the like, which is supplied to the audio encoder 112 (112-1 to 111-n) and the like. Is encoded.

[0005] Each encoded elementary stream is converted to a primary multiplexer 113 (11) corresponding to each program.
3-1 to 113-n). Each primary multiplexer 1
Reference numeral 13 denotes a time-division multiplexing of the elementary streams supplied for each program in units of transport packets (TS packets) specified by ISO / IEC13818-1, to generate a primary multiplexed stream corresponding to each program. .

[0006] The plurality of degree-multiplexed streams generated by the degree-one multiplexers 113 are supplied to a degree-one multiplexer 114. The secondary multiplexer 114 further time-division-multiplexes the plurality of primary multiplexed streams in units of TS packets,
Generate one secondary multiplexed stream.

[0007] The degree-two multiplexer 114 converts the generated degree-two multiplexed stream into the receiving device 3 via the transmission medium 200.
Supply to 00.

Here, the first-order multiplexed stream and the second-order multiplexed stream multiplexed by each of the first-order multiplexer 113 and the second-order multiplexer 114 correspond to a transport stream defined in ISO / IEC13818-1. ing.

As described above, the transmitting apparatus 100 compresses and encodes baseband video data and audio data corresponding to each program, generates one secondary multiplexed stream, and converts the generated secondary multiplexed stream. The data can be supplied to the receiving device 300 via the transmission medium 200.

[0010] The secondary multiplexed stream is transmitted to the receiving apparatus 300 via the transmission medium 200. The secondary multiplexed stream is supplied to a separator 311. Separator 311
For example, only the elementary stream corresponding to the program specified by the viewer or the like is separated from the secondary multiplexed stream and supplied to the video decoder 312 and the audio decoder 313. That is, the separator 311 supplies the video elementary stream of the specified program to the video decoder 312, and supplies the audio elementary stream of the specified program to the audio decoder 313.

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).

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.

FIG. 11 shows an example in which the primary multiplexer generates a transport stream composed of one program consisting of video and audio.
The program is not limited to a combination of video and audio, and a plurality of programs may be multiplexed in a transport stream output from the primary multiplexer.

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.

Each primary multiplexer divides a video elementary stream encoded by a video encoder and an audio elementary stream encoded by an audio encoder into fixed-length TS packets of 188 bytes, and the divided TS packets The primary multiplexing process is performed in units of time division to generate a primary multiplexed stream. Next, the secondary multiplexer performs a secondary multiplexing process on each primary multiplexed stream in a time-division manner in units of the TS packets to generate a secondary multiplexed stream. As described above, the primary multiplexed stream and the secondary multiplexed stream have a stream configuration multiplexed in TS packet units.

FIG. 13 shows the data structure of a 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 value (PC
R: Program Clock Reference) and stuffing_byte for size adjustment are encoded.

The PCR is a time reference value indicating the data arrival time (ie, the data output time at the multiplexer). In the receiving device, for example, P
By performing LL synchronization, the system clock of the transmitting device is restored.

FIG. 14 shows a decoder model of the receiving apparatus 300 when a transport stream specified by the above-described ISO / IEC13818-1 is supplied. ISO / IEC1
When generating the transport stream specified by 3818-1, the TS packets are scheduled and time-division multiplexed so that processing in the following decoder model does not break down.

The separator 311 selects, for example, only TS packets corresponding to the program specified by the viewer from the secondary multiplexed stream, and
4 to 306. Each transport buffer 30
4 to 306 store TS packets of corresponding data. For example, the transport buffer 304 stores a TS packet of video data of the selected program, the transport buffer 305 stores a TS packet of audio data of the selected program, and the transport buffer 306 stores the TS packet of the selected program. A TS packet of program control data of the generated program is stored.
Although a transport buffer for data other than audio and video is not shown here, if data and the like are included in the selected program, these TS packets are stored in the corresponding transport buffer.

Each transport buffer 304-306
Has a capacity of, for example, 512 Bytes, and as long as data is stored, TS at a prescribed bit rate.
The data_byte of the packet is leaked.

The video data leaked from the transport buffer 304 is transmitted to the multiplexing buffer 3
07. The transport buffer 30
The audio data and program control data leaked from 5,306 are supplied to corresponding elementary buffers 309, 310, respectively.

From the multiplexing buffer 307,
Only the elementary stream leaks at the prescribed bit rate and is supplied to the elementary buffer 308. At each decoding time, the decoders 311, 312, and 313 extract an elementary stream from a corresponding elementary buffer for each decoding unit (picture unit in the case of video data) called an access unit, and perform decoding processing. Note that the video data is decoded 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.

The receiving apparatus 300 performs the decoding processing of the transport stream defined by the above-described ISO / IEC13818-1 using the above model. As described above, the transmitting apparatus 100 transmits a transport stream in which data compressed for each of a plurality of programs is multiplexed,
The receiving apparatus 300 can separate and decode the data.

The primary multiplexer of the transmitting apparatus 100 time-division multiplexes the TS packets according to a schedule such that each buffer in the decoder model shown in FIG. 14 does not underflow or overflow.

By the way, in a multiplexing system such as that used in the above-mentioned broadcasting system, that is, a multiplexing system for generating a single secondary multiplexed stream by further multiplexing the primary multiplexed primary multiplexed stream. For the reasons given below, 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. Misalignment will occur.

(1) The secondary multiplexing can be performed only in the time slot of the 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 only one TS packet of the primary multiplexed stream can be secondary-multiplexed to a certain time slot, the TS packet of the primary multiplexed stream output from the primary multiplexer at substantially the same time is kept waiting. That

Here, the output timing of the degree-multiplexed stream scheduled by each degree-multiplexer,
The time lag that occurs between the output timing of the primary multiplexed stream multiplexed in the secondary multiplexed stream is called secondary multiplexing jitter.

Therefore, in such a multiplexing system,
Even if the primary multiplexing unit schedules the decoder buffer provided in the preceding stage of the decoder so as not to break down and generates a primary multiplexed stream, this secondary multiplexing jitter occurs, and the data stream arrives at the decoder buffer at the timing of arrival. A shift occurs, or a shift occurs in the time reference value encoded in the secondary multiplexed stream (PCR in the case of a transport stream defined in ISO13818-1). for that reason,
There has been a problem that the decoder buffer is broken by the influence of these shifts.

In order to solve the above problem, a pattern that defines 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. As a result, the present applicant discloses a multiplexing method for generating a secondary multiplexed stream without correcting the time reference value (PCR) while suppressing the secondary multiplexing jitter to a small extent. is suggesting.

The quadratic multiplexing method proposed in JP-A-11-215083 will be briefly described below with reference to FIG.

A plurality of degree-one multiplexed streams are input to the degree-two multiplexer. The secondary multiplexer sets a pattern that defines the TS packet selection order. This pattern is a pattern in which the order in which TS packets are extracted from a plurality of primary multiplexed streams and the secondary multiplexing is performed is determined in advance. The secondary multiplexer performs secondary multiplexing by repeating this pattern periodically. 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 the pattern and the bit rate of the secondary multiplexed stream. For example, program A and program B
Are multiplexed and the 1Mbp
When generating a secondary multiplexed stream of s, if one pattern includes three TS packets of program A and two TS packets of program B, the bit rate of program A is set to 600 kbps. , The bit rate of the program B 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. Then, each degree-multiplexer assigns a PCR to each TS packet number of the degree-multiplexed transport stream included in the pattern (for example, in the example of FIG. The program B adds a PCR for every two TS packets.), And it becomes possible to add a PCR to a fixed position in the pattern of the secondary multiplexed stream.

Note that the secondary multiplexing delay shown in FIG. 15 is a delay time that is fixedly generated when performing secondary multiplexing. Therefore, even if this secondary multiplexing delay occurs, there is no problem that the decoder buffer breaks down.

In the secondary multiplexing method proposed in Japanese Patent Application Laid-Open No. H11-215083, the reference clock Cp of the primary multiplexer and the reference clock of the secondary multiplexer are used.
If Cr is synchronized, the second-order multiplexing jitter occurs only up to a fixed amount fixed in the pattern. for that reason,
Since the upper limit of the secondary multiplexing jitter can be determined, if a primary multiplexed stream is generated by providing a margin for the upper limit in the capacity of the decoder buffer assumed in advance,
Even if quadratic multiplexing is performed, no failure occurs in the decoder buffer.

However, for example, when the first-order multiplexer and the second-order multiplexer are completely different devices, the reference clock Cp of the first-order multiplexer and the reference clock Cr of the second-order multiplexer are used.
And an asynchronous system must be configured. In the case of such an asynchronous system, Japanese Patent Laid-Open No.
In the secondary multiplexing method proposed in Japanese Patent Publication No. 215083, as shown in FIG. 16, even if secondary multiplexing is continued in a pattern, for example, the secondary multiplexing (Secondary multiplexing jitter) occurs, and the more the multiplexing proceeds, the more the secondary multiplexing jitter accumulates.

That is, when the bit rate P is assigned to each of the primary multiplexers based on the number of TS packets that are secondary-multiplexed in the pattern, the primary multiplexer receives the reference clock Cp of the primary multiplexer. The primary multiplexed stream of the bit rate P is output, and the secondary multiplexor secondary-multiplexes the primary multiplexed stream at the bit rate P of the secondary multiplexor at the reference clock Cr. As described above, when multiplexing is performed by using a unique reference clock, errors in the reference clock accumulate as secondary multiplexing jitter as the multiplexing proceeds.

Then, when the secondary multiplexing jitter accumulates,
Since the buffer in the receiving device overflows or underflows, and the secondary multiplexing timing of the PCR is shifted, a problem occurs that the receiving device cannot correctly restore the system clock on the transmission side.

In order to solve such a problem, a pattern that determines the time-division multiplexing order of TS packets extracted from the primary multiplexed stream is set in advance, and the TS packets are sequentially arranged from the primary multiplexed stream according to this pattern. A multiplexing method of multiplexing dummy data and canceling the accumulated secondary multiplexing jitter when the secondary multiplexing jitter exceeds a certain amount,
The present applicant has proposed in Japanese Patent Application Laid-Open No. H11-215082.

The quadratic multiplexing method proposed in JP-A-11-215082 will be briefly described below with reference to FIG. The second-order multiplexer performs the second-order multiplexing process proposed in the above-mentioned Japanese Patent Application Laid-Open No. H11-215083, and furthermore, the second-order multiplexing jitter D
(I) is monitored, and this secondary multiplexing jitter D
When (i) becomes equal to or larger than the threshold value, a dummy TS packet (for example, NULL TSP defined in ISO / IEC13818-1) is inserted to avoid the accumulation of the deviation of the secondary multiplexing timing. The quadratic multiplexer corrects and outputs the PCR in accordance with the quadrature multiplexing output timing. Further, the secondary multiplexing jitter D (i) is converted to a dummy TS packet (NU
In order to make correction possible by inserting LL TSP), the bit rate assigned to the primary multiplexer is assigned to be smaller than the bit rate P determined based on the number of TS packets to be secondary-multiplexed in the pattern. . For example, the maximum value of the system clock rating of the primary multiplexer is CpMAX
When the minimum value of the system clock rating of the quadratic multiplexer is CrMIN, the bit rate assigned to the primary multiplexer is (CrMIN / CpMAX) * P, so that quadratic multiplexing is always performed. The timing is in the direction of advance, and the dummy T
Correction can be made by inserting an S packet (NULL TSP).

However, Japanese Patent Application Laid-Open No. Hei 11-2
In the secondary multiplexing method proposed in Japanese Patent Publication No. 15082, even if PCR is added to each TS packet number of the primary multiplexed transport stream included in the pattern,
To correct the secondary multiplexing timing deviation, a dummy T
By inserting S packet (NULL TSP), PC
The position in the pattern of the TS packet to which R is added shifts. Alternatively, even if the primary multiplexer gives a PCR for each time period corresponding to the pattern, a dummy TS packet (NULL TSP) is inserted to correct the secondary multiplex timing shift, and the PCR is added. The position in the pattern of the TS packet to which is added is shifted.

For example, as shown in FIG.
When a primary multiplexed stream of the program A having a bit rate of ps is multiplexed to generate a secondary multiplexed stream of 1 Mbps, the T of the program A is included in one pattern.
That is, three S packets are included. Then, the first-order multiplexer receives the TS to which the PCR is assigned every three packets.
If the packet has been transmitted, the TS packet to which the PCR is assigned is arranged at a fixed position in the pattern (the first packet of the pattern in FIG. 17). 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]

By the way, in terrestrial digital broadcasting, an OFDM system is generally adopted as a broadcasting wave modulation system in order to reduce the influence of reception interference due to multipath. ISDB-T (Intergrated Services Digital), a terrestrial digital broadcasting system in Japan
Broadcasting-Terrestorial) also employs the OFDM method. In this OFDM system, modulation is performed by performing IFFT (Inverse Fast Fourier Transform) during transmission and FFT (Fast Fourier Transform) during reception.

This ISDB-T employs a method called partial reception, which can receive only a signal in a partial frequency band among OFDM signals transmitted to one frequency channel. When broadcasting using this partial reception method, by a wideband receiver that can receive all the signals of one frequency channel and a narrowband receiver that can receive only a part of the signals of one frequency channel, The broadcast can be received. By adopting such a partial reception system, for example, only an audio signal of a television broadcast can be received by an audio receiver, and only main information can be received by a narrow band receiver, but additional information can be received. When it is desired to receive information, it is possible to receive the information with a broadband receiver, so that the broadcast can have expandability.

Here, when such a partial reception system is adopted, one transport stream is basically broadcast on one frequency channel.
The wideband receiver can receive all the TS packets of the transport stream broadcast on the frequency channel, whereas the narrowband receiver can receive the TS broadcast on the frequency channel. Only a part of the TS packet of the port stream can be received.

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. The receiver can receive only some of them (for example, two TS packets).

Therefore, some packets received by the narrowband receiver must be multiplexed so as to include PCR so as to correctly restore the system clock to generate a transport stream.

However, as described above, when the secondary multiplexed stream (transport stream) is generated in such a manner that the secondary multiplexed jitter is adjusted with the dummy data, the primary multiplexed stream side is provided with a fixed packet. Even if a PCR is periodically inserted into the pattern, if a dummy packet is inserted during the secondary multiplexing, the position of the TS packet to which the PCR is added in the pattern is shifted. Therefore, it is impossible to insert a TS packet to which a PCR has been added 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 recover the system clock when partial reception is performed by the narrowband receiver is Transmission was not possible from the transmitting device.

The present invention has been made in view of the above circumstances, and can generate a primary multiplexed stream and a secondary multiplexed stream based on an asynchronous reference clock, and can also generate a secondary multiplexed stream. , The time reference reference value can be arranged at a certain position, and the receiving side can reliably restore the system clock even in the receiving system that receives only a part of the packets in the secondary multiplexed stream. It is an object to provide a digital signal multiplexing apparatus and method.

[0048]

In a digital signal multiplexer according to the present invention, a bit stream of a digital signal is multiplexed in a time division manner in packet units, and a time indicating an output timing of the bit stream in the bit stream. One or more first-order multiplexed streams including the reference value are received from one or more first-order multiplexers, and each received first-ordered multiplexed stream is time-division multiplexed in packet units to generate a second-order multiplexed stream. Receiving means for receiving each degree-multiplexed stream from each degree-multiplexing apparatus, and a time-based reference value assigned to each degree-multiplexed stream received by the receiving means. Means for separating packets into packets having no time reference value, and a time reference value. A packet by multiplexing packets and time standard reference value that is granted is not applied,
Secondary multiplexing means for generating a secondary multiplexed stream in which one or more of the primary multiplexed streams are multiplexed in packet units, wherein the secondary multiplexing means comprises a time reference for each of the primary multiplexed streams. Packets to which reference values are assigned are arranged in the secondary multiplexed stream at predetermined packet periods.

In the digital signal multiplexing apparatus, at the time of performing the secondary multiplexing, the packets to which the time reference reference values for the respective primary multiplexed streams are added in the secondary multiplexed stream at predetermined packet periods. To place.

In the digital signal multiplexing method according to the present invention, the bit stream of the digital signal is time-division multiplexed in packet units, and the bit stream includes a time reference value indicating the output timing of the bit stream. A digital signal multiplexing method for receiving one or more primary multiplexed streams and multiplexing the received primary multiplexed streams in packet units in a time-division manner to generate a secondary multiplexed stream. Receiving a stream, separating each received primary multiplexed stream into packets to which a time reference value is assigned and packets to which no time reference value is assigned, and Multiplexing a packet having no time-base reference value and a packet to which one or more primary multiplexes have been added. A secondary multiplexed stream in which the streams are multiplexed in units of packets is generated, and when multiplexing the secondary multiplexed stream, a packet to which a time reference reference value for each primary multiplexed stream is assigned is determined. It is characterized in that it is arranged in the secondary multiplexed stream for each packet cycle.

In the digital signal multiplexing method, when performing the secondary multiplexing, the packet to which the time reference reference value for each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. I do.

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multiplexing system to which the present invention is applied will be described as an embodiment of the present invention.

The multiplexing system according to the embodiment of the present invention comprises:
A digital satellite broadcasting system for transmitting a transport stream in which data is multiplexed for each of a plurality of programs (for example, a service in which broadcast programs in television broadcasting are continuously arranged), and recording this transport stream on a recording medium Applied to recording systems and the like.
This multiplexing system is composed of a plurality of primary multiplexed streams obtained by multiplexing compressed data streams (elementary streams) such as audio and video in a time-division manner, and further multiplexing the time-division multiplexed streams into one transponder usable by one transponder Is a system that generates a secondary multiplexed stream of Here, the primary multiplexed stream corresponds to the television broadcasting service described above. Note that both the primary multiplexed stream and the secondary multiplexed stream have I
The following description is made on the assumption that the data stream is a data stream corresponding to the transport stream defined by SO13818-1.

First Embodiment (System Configuration) First, a multiplexing system according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a multiplexing system according to the first embodiment of the present invention.

The multiplexing system 1 is, as shown in FIG.
A plurality of degree-one multiplexers 1 for generating a degree-one multiplexed stream
1-1 to 11-n and a secondary multiplexer 12 that further multiplexes the primary multiplexed streams generated by the respective primary multiplexers 11-1 to 11-n to generate a secondary multiplexed stream. Have. The secondary multiplexing unit 12 receives the primary multiplexed streams generated by the primary multiplexing units 11-1 to 11-n, and processes a plurality of the receiving units 13-1 to 13-13. n and each of the receiving units 13-1 to 13-n
Selecting unit 14 for selecting and quadratic multiplexing the primary multiplexed stream output from, and receiving units 13-1 to 13-n
Controller 1 that controls the secondary selection unit 14
5 is provided.

Each of the degree-one multiplexers 11-1 to 11-n provides a predetermined margin to the upper and lower limits of the buffer occupancy of the virtual decoder buffer, and sets a code amount such that the virtual decoder buffer does not fail. To generate a first-order multiplexed stream. Each primary multiplexed stream is supplied to the corresponding receiving unit 13-1 to 13-n. Each primary multiplexers 11-1 to 11-n are operated based on an independent reference clock _Cp 1 ~ CP _n together. Primary multiplexed is generated by the primary multiplexers 11-1 to 11-n stream is synchronized to each reference clock _Cp 1 _{~Cp n.}

Each of the degree-multiplexed streams output from each of the degree-one multiplexers 11-1 to 11n is input to a corresponding one of the receiving units 13-1 to 13-n in the degree-two multiplexer 12.

The quadratic multiplexer 12 operates based on the reference clock Cr. The reference clock Cr is supplied to each of the primary multiplexers 11-1 to 11-n.
₁ ~ CP _n and synchronization has not been taken, the primary multiplexer 1
1-1 to 11-n and the second-order multiplexer 12 operate asynchronously.

Each of the receiving units 13-1 to 13-1 of the secondary multiplexer 12
3-n designates a separating unit 16 for separating the primary multiplexed stream into TS packets to which PCR is added and other TS packets, a PCR correcting unit 17 for correcting PCR,
An intermediate memory 18 for temporarily storing packets other than the TS packet to which the CR is added, and a NULL packet (ISO /
A TSP generator 19 that generates a TS packet including system information (defined by IEC13818-1) and system information (defined by ISO / IEC13818-1 and each broadcasting standard), a PCR corrector 17, an intermediate memory 18, and a TSP generator 19. A primary selection unit 20 for selecting and multiplexing each output packet.

The separating unit 16 in each receiving unit 13 separates the input primary multiplexed stream into TS packets to which PCR has been added and other TS packets in units of TS packets. Whether the PCR is added to the TS packet can be determined by referring to the PCR_flag in the adaptation_field. Adaptation_f in TS packet
If an ield is provided and the PCR_flag in the adaptation_field is set to 1, a PCR is assigned to the TS packet. The separation unit 16 supplies the TS packet to which the PCR has been added to the PCR correction unit 17,
The other TS packets are supplied to the intermediate memory 18.

The PCR corrector 17 corrects the PCR value described in the TS packet. More 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 occurring in the packet, Calculate the PCR value to be the correct value,
Rewrite the PCR with the calculated value. PCR correction unit 17
Is, when selected by the primary selection unit 14 at the subsequent stage,
The TS packet to which R is added is output.

The intermediate memory 18 temporarily stores packets other than the TS packet to which the PCR is added. The intermediate memory 18 outputs the TS packets in the order received from the primary multiplexer 11 when selected by the subsequent primary selection unit 14.

The TSP generation section 19 generates a NULL packet to be inserted for performing timing correction at the time of performing the degree-two multiplexing, and a TS packet storing system information and the like. The TSP generation unit 19 outputs the generated TS packet when selected by the subsequent primary selection unit 14.

The primary selection unit 20 performs the PCR correction unit 17, the intermediate memory 18, and the intermediate memory 18 so that the packet to which the PCR has been added is inserted for every fixed packet in the secondary multiplexed stream.
The TS packets output from the TSP generator 19 are appropriately selected and multiplexed. The multiplexing timing will be described later in detail.

Each of the receiving units 13 as described above corrects the PCR value of the input primary multiplexed stream,
A NULL packet and a TS packet storing system information are inserted, a primary multiplexed stream is processed and output.

The secondary selecting section 14 of the secondary multiplexer 12 converts the primary multiplexed stream output from each receiving section 13 into a TS.
The extracted TS packets are time-division multiplexed in units of packets to generate a secondary multiplexed stream.

The system controller 15 of the secondary multiplexer 12 controls each of the receiving units 13 and the secondary selecting unit 14.

In the multiplexing system 1 having the above configuration, the secondary selection unit 14 and the primary selection unit 20 in the reception unit 13
Multiplexes a plurality of primary multiplexed streams into one secondary multiplexed stream.

(Multiplexing System of Multiplexing System 1) Here, in the multiplexing system 1, the packets to which the PCR regarding each primary multiplexed stream is assigned by the secondary selection unit 14 and the primary selection unit 20 are: The TS is placed in the secondary multiplexed stream every predetermined packet period.
You are selecting a packet.

For example, as shown in FIG. 2, when multiplexing two primary multiplexed streams (one is a program A and the other is a program B) to generate a secondary multiplexed stream, For example, a TS packet to which a PCR is added is always arranged every 9 packets, and a TS packet to which a PCR for the program B is added is always arranged every 3 packets, for example.

Hereinafter, P regarding each degree-multiplexed stream will be described.
The first to fifth processing methods for switching selection so that the packet to which the CR is assigned are arranged in the secondary multiplexed stream at predetermined packet periods will be specifically described.

--First Processing Method-- First, the first processing method will be described.

In the first processing method, a multiplexing process is performed by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set by the secondary selection unit 14. This selection pattern is a repetition pattern for selecting TS packets, which defines the order of TS packets to be selected from each degree-multiplexed stream when generating a degree-multiplexed stream. The secondary selection unit 14 selects 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. .

This selection pattern is determined as follows.

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.

Subsequently, distribution is made to each primary multiplexed stream at each packet position in the selection pattern. For example, when two transport streams (primary multiplexed streams) of a program A and a program B are secondarily multiplexed, three out of five TS packets are transmitted as shown in FIG. Assigned to program A (first, third, fifth packet in selection pattern),
Two packets are allocated to program B (the second and fourth packets in the selection pattern).

Subsequently, the bit rate of each primary multiplex stream is determined from the bit rate of the secondary multiplex stream and the number of TS packets distributed to each primary multiplex stream. For example, if the bit rate of the secondary multiplexed stream is 1 Mbps, the program A is allocated to 600 kbps and the program B is allocated to 400 kbps as shown in FIG. These are referred to as assigned bit rates of the respective degree multiplexers.

As described above, the selection pattern and the bit rate of the primary multiplexed stream are determined. If the bit rate of the primary multiplexed stream is determined in advance, the selection pattern may be determined in reverse from the bit rate ratio of each primary multiplexed stream.

The secondary selecting section 14 sequentially selects the primary multiplexed stream according to the set selection pattern and performs secondary multiplexing.

By performing quadratic multiplexing according to the preset selection pattern in this way, the quadratic multiplexing jitter can be set to a known value. Therefore, by generating the primary multiplexed stream with a margin corresponding to the secondary multiplexing jitter determined according to the selection pattern, the decoding side does not fail even after the secondary multiplexing.

In the first processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets to which PCRs are assigned are arranged for every fixed number of packets. The generation interval of the TS packet to which the PCR is assigned is an interval corresponding to the number of packets assigned to the selection pattern.

For example, a selection pattern composed of five TS packets is set, and three TS packets are stored in the program A.
When packets are allocated and two TS packets are allocated to the program B, as shown in FIG. 4A, the primary multiplexer 11 that generates the program A assigns a PCR every three packets. The primary multiplexer 11 that generates the program B outputs a TS packet to which PCR has been added for every two packets.

As described above, each of the degree-one multiplexers 11 transmits the TS to which the PCR is assigned for each assigned packet number.
By generating the primary multiplexed stream in which the packets are inserted, when the secondary multiplexed stream is generated, the packet to which the PCR relating to each primary multiplexed stream is assigned is converted into the secondary multiplexed stream every predetermined packet cycle. It will be arranged in. For example, as shown in FIG. 4B, it is possible to generate a secondary multiplexed stream in which the PCR for the program A and the PCR for the program B are arranged every five packets.

The multiplexing system 1 is an asynchronous system in which the reference clocks of the first-order multiplexer 11 and the second-order multiplexer 12 are not synchronized.

That is, in 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 synchronization is carried out according to the selected pattern, so that the secondary The multiplexing jitter does not become a value exceeding a certain amount, and the secondary multiplexing jitter does not increase. For example,
As shown in FIG. 5A, in the case of the 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.

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 the secondary clock is secondary-multiplexed according to the selected pattern, The error resulting from the difference between the two accumulates and the secondary multiplexing jitter increases. For example, as shown in FIG.
If the reference clock Cr of No. 2 is larger than the reference clock Cp of the primary multiplexer 11, the multiplexing timing of each packet advances, and as the multiplexing progresses, the secondary multiplexing jitter increases. . In addition, when performing the degree-two multiplexing, a degree-two multiplexing delay which actually occurs fixedly in each packet also occurs. However, in order to easily explain the increase of the degree-two multiplexing jitter, FIG. It is abbreviated.

When the secondary multiplexing jitter increases in this way, the difference between the PCR value and the actual reception timing increases, and the processing of the decoder breaks down.

Therefore, in the first processing method, the output timing of the secondary multiplexed stream temporally advances with respect to the reception timing of the primary multiplexed stream. When it becomes
Forcibly insert dummy data (NULL packet),
Reduce second order multiplexing jitter.

For example, as shown in FIG.
-Order multiplexing jitter D (2) of TS packet (b2)
Is not more 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, in the original selection pattern, T
The dummy data (NULL packet) is inserted into the area of the secondary multiplexed stream where the S packet (b5) was to be secondary-multiplexed.

Further, in order to arrange the TS packet to which the PCR has been assigned in the secondary multiplexed stream at a predetermined packet cycle, the packet to which the PCR has been added is moved to a predetermined position in the selection pattern. , The order of selecting 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.

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 placed at the second packet position of the selection pattern. Then, the TS packet (b5) to which no PCR is assigned is arranged at the fourth packet position of the selection pattern. Then, the PCR value added to the TS packet (b6) is corrected to a correct PCR value when the secondary multiplexed output is performed with reference to the originally attached value. Thereafter, the TS packet (b8) to which the PCR is added and the TS packet (b1
0), the selection is switched so that the TS packet (b12)... Is always arranged at the second packet position in the selection pattern, and the PCR value is corrected.

As described above, in the first processing method, an increase in the degree-two multiplexing jitter due to the asynchronous system is corrected by inserting the dummy data (NULL packet) into the degree-two multiplexed stream. Further, in the first processing method, the shift in the position where the PCR is assigned due to the insertion of the dummy data (NULL packet) is determined by switching the TS packet selection order and correcting the PCR.
Fix it. By performing such processing, in the first processing method, the PCR regarding each primary multiplexed stream is performed.
Can be switched so that the TS packet to which the is added is arranged in the secondary multiplexed stream at every predetermined packet period.

In the first processing method, the secondary multiplexing jitter is corrected on the assumption that the output timing of the secondary multiplexed stream temporally advances with respect to the reception timing of the primary multiplexed stream. It will be. Therefore, if it is compensated that the reference clock Cr of the secondary multiplexer 12 becomes faster than the reference clock Cp of the primary multiplexer 11, the secondary processing can be surely performed by the first processing method. Can be.

The reference clock Cr of the secondary multiplexer 12 is
To compensate for the fact that the reference clock is faster than the reference clock Cp of the primary multiplexer 11, for example, the maximum value of the reference clock rating of the primary multiplexer is CpMAX, the minimum value of the reference clock rating 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 may be set as follows.

(CrMIN / CpMAX) × P As dummy data for adjusting secondary multiplexing jitter, not only NULL packets but also TS packets in which system information is described may be inserted.

--Second Processing Method-- Next, the second processing method will be described.

In the second processing method, a multiplexing process is performed by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set by the secondary selection unit 14. This selection pattern is determined in the same manner as in the first processing method described above.

In the second processing method, each primary multiplexer 11 outputs a primary multiplexed stream in which TS packets to which PCRs are 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.

For example, assuming that 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 )
Becomes At this time, as shown in FIG. 7A, the primary multiplexer 11 outputs a TS packet to which PCR has been added for each cycle T. Each primary multiplexer 11 has at least a period T
If a TS packet with a PCR inserted is output every time, other TS packets may be thinned out freely, or dummy data (NULL packet) may be inserted.

As described above, each primary multiplexer 11 generates a secondary multiplexed stream by inserting a TS packet to which a PCR is added at each cycle T of a selection pattern, thereby generating a secondary multiplexed stream. At this time, the packet to which the PCR regarding each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet cycle. For example, as shown in FIG. 7B, it is possible to generate a secondary multiplexed stream in which the PCR for the program A and the PCR for the program B are arranged every five packets. If some of the packets of the primary multiplexed stream are thinned out or replaced by dummy packets, data will not exist at a predetermined packet position in the secondary multiplexed stream. There is. In this case, a NULL packet or a TS packet in which system information is described is inserted into the empty packet position.

Further, in the second processing method, similarly to the first processing method, the output timing of the secondary multiplexed stream temporally advances with respect to the reception timing of the primary multiplexed stream. Dummy data (NULL packet) when the next multiplexing jitter exceeds a certain threshold
To reduce the secondary multiplexing jitter.

Further, in order to arrange the packet to which the PCR is added in the secondary multiplexed stream at a predetermined packet cycle, the packet to which the PCR is added is placed at a predetermined position in the selection pattern. The selection order of the TS packets in the primary multiplexed stream is switched so as to be arranged. 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.

As described above, in the second processing method, an increase in the secondary multiplexing jitter due to the asynchronous system is corrected by inserting the dummy data (NULL packet). Further, in the second processing method, the shift of the position where the PCR is provided due to the insertion of the dummy data (NULL packet) is corrected by switching the TS packet selection order and correcting the PCR. By performing such processing, in the second processing method, the switching selection is performed such that the packet to which the PCR regarding each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period. Can be.

Also, in the second processing method, as in the first processing method, it is assumed that the output timing of the secondary multiplexed stream temporally advances with respect to the reception timing of the primary multiplexed stream. , The secondary multiplexing jitter is corrected. Therefore, even in this second processing method,
As shown in the following equation, the reference clock C of the secondary multiplexer 12
r is faster than the reference clock Cp of the primary multiplexer 11.

(CrMIN / CpMAX) × P--Third Processing Method-- Next, the third processing method will be described.

In the third processing method, a multiplexing process is performed by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set by the secondary selection unit 14. This selection pattern is determined in the same manner as in the first processing method described above.

In the third processing method, the primary multiplexed streams in which the TS packets to which the PCR is assigned are arranged for every fixed number of packets are output from each primary multiplexer 11. The generation interval of the TS packet to which the PCR is assigned is an interval corresponding to the number of packets assigned to the selection pattern. T to which this PCR is assigned
The S packet generation interval is determined in the same manner as in the above-described first processing method.

In the third processing method, the output timing of the secondary multiplexed stream is delayed in time with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexed jitter exceeds a certain threshold. Then, dummy data (NULL packet) is forcibly deleted from the primary multiplexed stream to reduce secondary multiplexing jitter. In addition,
In order to make it possible to forcibly delete the dummy data, the primary multiplexer 11 previously sets the dummy data (NU) at appropriate intervals.
A primary multiplexed stream into which an LL packet has been inserted is generated.

For example, as shown in FIG.
-Order multiplexing jitter D (2) of TS packet (b2)
Is not more 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, a NULL packet (here, b5) next to the TS packet (b4) is deleted.

Further, in order to arrange the packet to which the PCR has been added in the secondary multiplexed stream at a predetermined packet cycle, the packet to which the PCR has been added is placed at a predetermined position in the selection pattern. The selection order of the TS packets in the primary multiplexed stream is switched so as to be arranged. 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.

Here, as shown in FIG. 8, a PCR is added to the TS packet (b6) after the NULL packet is deleted.
Are added, the selection order of the TS packet (b6) and the TS packet (b7) is switched, the TS packet (b6) is arranged at the second packet position in the selection pattern, and no PCR is added. TS packet (b7)
At the fourth packet position of the selection pattern. Then, the PC assigned to this TS packet (b6)
The value of R is corrected to a correct PCR value when a quadratic multiplex output is performed with reference to the originally attached value. Since then
The selection switching is performed so that the TS packet (b8), the TS packet (b10), the TS packet (b12)... To which the PCR is assigned is always arranged at the second packet position in the selection pattern, and the PCR is performed. The value is corrected.

As described above, in the third processing method, the dummy data (NULL packet) is deleted from the primary multiplexed stream to correct the increase in the secondary multiplexing jitter due to the asynchronous system. Further, in the third processing method, the shift of the PCR assignment position due to the deletion of the dummy data (NULL packet) is corrected by switching the TS packet selection order and correcting the PCR. By performing such processing, in the third processing method, the P for each degree-multiplexed stream is
Switching can be selected so that the packet to which the CR is assigned is arranged in the secondary multiplexed stream every predetermined packet cycle.

In the third processing method, the secondary multiplexing jitter is corrected on the assumption that the output timing of the secondary multiplexed stream is temporally delayed from the reception timing of the primary multiplexed stream. It will be. Therefore, by compensating that the reference clock Cr of the secondary multiplexer 12 becomes slower than the reference clock Cp of the primary multiplexer 11, the secondary processing can be surely performed by the third processing method. it can.

When the reference clock Cr of the secondary multiplexer 12 is
To compensate for the delay of the reference clock Cp of the primary multiplexer 11, for example, the maximum value of the reference clock of the primary multiplexer is set to CpMAX, and the minimum value of the reference clock of the secondary multiplexer is set to CpMAX. 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 may be set as follows.

(CpMAX / CrMIN) × P—Fourth Processing Method— Next, the fourth processing method will be described.

In the fourth processing method, a multiplexing process is performed by the secondary selection unit 14 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.

In the fourth processing method, a primary multiplexed stream in which TS packets to which PCRs are assigned at regular time intervals is output from each primary multiplexer 11. 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 above-described second processing method.

In the fourth processing method, similarly to the third processing method, the output timing of the secondary multiplexed stream is temporally delayed with respect to the reception timing of the primary multiplexed stream. When the next-order multiplexing jitter exceeds a certain threshold, dummy data (NULL packet) is forcibly deleted from the first-order multiplexed stream to reduce the second-order multiplexing jitter.

Further, in order to arrange the packet to which the PCR has been assigned in the secondary multiplexed stream at a predetermined packet cycle, the packet to which the PCR has been added is placed at a predetermined position in the selection pattern. The selection order of the TS packets in the primary multiplexed stream is switched so as to be arranged. 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.

As described above, in the fourth processing method, the dummy data (NULL packet) is deleted to correct the increase of the secondary multiplexing jitter due to the asynchronous system. Further, in the fourth processing method, a shift in the position at which a PCR is assigned due to the deletion of dummy data (NULL packet) is corrected by switching the TS packet selection order and correcting the PCR. By performing such processing, in the fourth processing method, the switching selection is performed so that the packet to which the PCR regarding each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet cycle. Can be.

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 temporally delayed with respect to the reception timing of the primary multiplexed stream. , The secondary multiplexing jitter is corrected. Therefore, as shown in the following equation, the reference clock Cr of the secondary multiplexer 12 is
To be faster than the reference clock Cp.

(CpMIN / CrMIN) × P--Fifth Processing Method-- Next, the fifth processing method will be described.

In the fifth processing method, a multiplexing process is performed by determining a selection pattern in which a switching order for selecting a primary multiplexed stream is set by the secondary selection unit 14. This selection pattern is determined in the same manner as in the first processing method described above.

In the fifth processing method, a primary multiplexed stream in which TS packets to which PCRs are assigned for every fixed number of packets is output from each primary multiplexer 11. The generation interval of the TS packet to which the PCR is assigned is an interval corresponding to the number of packets assigned to the selection pattern. T to which this PCR is assigned
The S packet generation interval is determined in the same manner as in the above-described first processing method. In the fifth processing method, the second
In the same manner as in the processing method described above, the primary multiplexed stream in which the TS packets to which the PCR is assigned may be arranged at each time interval may be output from each primary multiplexer 11.

Also, in the fifth processing method, the output timing of the secondary multiplexed stream temporally advances with respect to the reception timing of the primary multiplexed stream. When this happens, dummy data (NULL packet) is forcibly inserted to reduce the secondary multiplexing jitter. At the same time, in the fifth processing method, the output timing of the secondary multiplexed stream is temporally delayed with respect to the reception timing of the primary multiplexed stream, and the secondary multiplexed jitter becomes equal to or more than a certain threshold. Then, dummy data (NULL packet) is forcibly deleted from the primary multiplexed stream to reduce secondary multiplexing jitter.

That is, in the fifth processing method, the dummy data is both deleted from the primary multiplexed stream and the dummy data is inserted into the secondary multiplexed data to reduce the secondary multiplexing jitter. .

Further, in order to arrange the packet to which the PCR has been assigned in the secondary multiplexed stream at every predetermined packet period, the packet to which the PCR has been added is placed at a predetermined position in the selection pattern. The selection order of the TS packets in the primary multiplexed stream is switched so as to be arranged. 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.

As described above, in the fifth processing method, an increase in the degree-two multiplexing jitter due to the asynchronous system is corrected by inserting and deleting dummy data (NULL packet). Further, in the fifth processing method,
The shift in the position at which the PCR is provided due to the insertion and deletion of the dummy packet (NULL packet) is corrected by switching the TS packet selection order and correcting the PCR. By performing such processing, in the fifth processing method, the P for each degree-multiplexed stream is
Switching can be selected so that the packet to which the CR is assigned is arranged in the secondary multiplexed stream every predetermined packet cycle.

In the fifth processing method, it is not assumed that the output timing of the secondary multiplexed stream is advanced or delayed with respect to the reception timing of the primary multiplexed stream. Therefore, the processing can be performed without compensating the reference clocks of the first-order multiplexer 11 and the second-order multiplexer 12.

Second Embodiment Next, a multiplexing system according to a second embodiment of the present invention will be described with reference to the drawings. Note that this second
In describing the multiplexing system of this embodiment, the same components as those of the multiplexing system 1 of the above-described first embodiment are denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted.

FIG. 9 is a block diagram showing a multiplexing system according to the second embodiment of the present invention.

As shown in FIG. 9, the multiplexing system 30 includes a plurality of degree-one multiplexers 11-1 to 11-n for generating a degree-multiplexed stream, and the degree-one multiplexers 11-1 to 11-n.
n-order multiplexer 3 for further multiplexing the degree-one multiplexed stream generated by n.
2 is provided. The second-order multiplexer 32 receives a first-order multiplexed stream generated by each of the first-order multiplexers 11-1 to 11-n, and processes a plurality of the receiving streams 33-1 to 33-33. -n and each of the receiving units 33-1 to 33-1
A secondary selecting unit 34 for selecting and secondary multiplexing the primary multiplexed stream output from 33-n, and each receiving unit 33-1
33-n and a system controller 15 for controlling the secondary selection unit 34.

Each of the degree-multiplexed streams output from each of the degree-multiplexers 11-1 to 11n is input to a corresponding one of the receiving units 33-1 to 33-n in the degree-two multiplexer 32.

The secondary multiplexer 32 operates based on the reference clock Cr. The reference clock Cr is supplied to each of the primary multiplexers 11-1 to 11-n.
₁ ~ CP _n and synchronization has not been taken, the primary multiplexer 1
1-1 to 11-n and the second-order multiplexer 32 operate asynchronously.

Each of the receiving units 33-1 to 3-3 of the secondary multiplexer 32
3-n designates a separating unit 36 for separating the primary multiplexed stream into TS packets to which PCR has been added and other TS packets, and the P assigned to the primary multiplexed stream.
A PCR deleting section 37 for deleting a CR, a PCR generating section 38 for newly generating a PCR, and an intermediate memory 3 for temporarily storing packets other than the TS packet to which the PCR is added.
9 and NULL packet (specified in ISO / IEC13818-1) and system information (specified in ISO / IEC13818-1 and each broadcasting standard)
TSP generating unit 40 that generates a TS packet containing
And a primary selection unit 41 that selects and multiplexes each packet output from the PCR deletion unit 37, the PCR generation unit 38, the intermediate memory 39, and the TSP generation unit 40.

The separating unit 36 in each receiving unit 33 separates the input primary multiplexed stream into TS packets to which PCR has been added and other TS packets in units of TS packets. Whether the PCR is added to the TS packet can be determined by referring to the PCR_flag in the adaptation_field. The separation unit 36 supplies the TS packet to which the PCR has been added 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 deleting section 37 performs a process of replacing the PCR originally assigned to the primary multiplexed stream with dummy data. Specifically, as shown in FIG.
If the PCR is described in the TS packet, adapt
Set the value of PCR_Flag described in tation_field to “1”
Is described, and a PCR is encoded in the following 6 bytes. The PCR deletion unit 37 replaces the value of the 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, adaptation_f
without changing the byte length of the ield and TS packets
The PCR can be deleted.

The PCR generation section 38 generates a TS packet to which a new PCR to be inserted when performing the secondary multiplexing is added. Specifically, based on the PCR originally calculated by the primary multiplexing unit 11, a PC that has a correct value when the TS packet is output as a secondary multiplexed stream.
An R value is calculated, and a TS packet to which a PCR of the calculated value is added is generated. The PCR correction section 38, when selected by the subsequent primary selection section 41,
Output a packet.

The intermediate memory 39 temporarily stores packets other than the TS packet to which the PCR has been added. The intermediate memory 39 outputs the TS packets in the order received from the primary multiplexer 11 when selected by the subsequent primary selection unit 41.

The TSP generating section 40 generates a NULL packet to be inserted for performing timing correction at the time of performing the degree-two multiplexing, and a TS packet storing system information and the like. The TSP generation unit 40 outputs the generated TS packet when selected by the subsequent primary selection unit 41.

[0142] The primary selection unit 41 determines whether the T
The TS packet output from the PCR deletion unit 37, the PCR generation unit 38, the intermediate memory 39, and the TSP generation unit 40 is appropriately selected so that the S packet is inserted at every fixed packet in the secondary multiplexed stream. Multiplexing. The multiplexing timing will be described later in detail.

Each of the receiving units 33 as described above corrects the value of the PCR for the input primary multiplexed stream,
A NULL packet and a TS packet storing system information are inserted, a primary multiplexed stream is processed and output.

The secondary selecting section 34 of the secondary multiplexer 32 converts the primary multiplexed stream output from each receiving section 33 into a TS.
The extracted TS packets are time-division multiplexed in units of packets to generate a secondary multiplexed stream.

The system controller 35 of the secondary multiplexer 32 controls each of the receiving units 33 and the secondary selecting unit 34.

In the multiplexing system 30 having the above configuration, the primary selection unit 41 in the secondary selection unit 34 and the reception unit 33
Multiplexes a plurality of primary multiplexed streams into one secondary multiplexed stream.

(Multiplexing System of Multiplexing System 30) In the multiplexing system 30, the secondary selection section 34 and the primary selection section 41 use the PC for each primary multiplexed stream.
The TS packets are selected so that the packet to which R is assigned is arranged in the secondary multiplexed stream at every predetermined packet cycle.

The system for switching and selecting the packets to which the PCRs for each primary multiplexed stream are assigned in the secondary multiplexed stream at predetermined packet periods is described in the first embodiment. This is the same as the first to fifth processing methods of the embodiment.

However, since the TS packet to which the PCR has been added is newly generated by the PCR generation unit 38,
The selection is made from the output of the generation unit 38. The bit rate P that can be assigned to each degree-of-order multiplexer is calculated in consideration of the number of newly generated TS packets (TS packets to which PCR has been added). For example, FIG.
As shown in the figure, the bit rate of the secondary multiplexed stream is 1 Mbps, and a selection pattern composed of five TS packets is set.
It is assumed that two TS packets are allocated to two TS packets and the program B. Then, it is assumed that a TS packet to which one PCR is added to both the program A and the program B is 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.

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 performing the secondary multiplexing, the respective primary multiplexed streams are used. The packet to which the PCR is assigned is arranged in the secondary multiplexed stream every predetermined packet cycle.

As a result, the multiplexing systems 1, 30
In the first embodiment, the first-order multiplexed stream and the second-order multiplexed stream can be generated based on an asynchronous reference clock, and the second-order multiplexing jitter is reduced so that the processing on the receiving side and the decoding side is not broken down. A secondary multiplexed stream can be generated. Further, in the multiplexing systems 1 and 30, the time reference reference value can be arranged at a fixed position in the secondary multiplexed stream, and the receiving system receives only a part of the TS packets in the secondary multiplexed stream. Even so, the system clock can be reliably restored on the receiving side.

For example, in a digital broadcasting system employing the OFDM modulation system or the like, in a broadcasting system in which only a partial band signal in one broadcast frequency channel is extracted and receivable, a single transport system is realized. There is a case where only a part of the TS packet in the stream is decoded. Even in the case of such partial reception, in the present invention, the PCR can be reliably included in the extracted partial TS packet, and the receiving side can reliably restore the system clock.

In describing the switching processing of the multiplexing system according to the embodiment of the present invention, a packet to which a PCR has been added is inserted into a secondary multiplexed stream at predetermined packet periods using a selection pattern. An example of the processing for arranging is shown. However, in the present invention, the switching process may be performed without setting such a selection pattern. For example,
The secondary multiplexing process may be performed by selecting TS packets in order from the primary multiplexed stream in which the number of packets stored in the intermediate memories 18 and 39 is large, or may be selected in order from the TS packet received earlier. Secondary multiplexing processing may be performed. However, even in such a case,
The switching process is performed so that the packet to which the PCR regarding each primary multiplexed stream is assigned is arranged in the secondary multiplexed stream every predetermined packet period.

Although the secondary multiplexing jitter is shown in the drawing as being detected at the head timing of the TS packet, if the detection position in the TS packet is fixed, it is added to the head of the TS packet. However, the jitter may be detected at any data position in any TS packet.

[0155]

In the digital signal multiplexing apparatus and method according to the present invention, when performing the secondary multiplexing, the packet to which the time reference reference value for each of the primary multiplexed streams is added is transmitted every predetermined packet period. Is placed in the secondary multiplexed stream.

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 multiplexed jitter can be generated. And a secondary multiplexed stream that does not break the processing on the receiving side or the decoding side can be generated. Furthermore, in this digital signal multiplexing apparatus, a time reference reference value can be arranged at a fixed position of a secondary multiplexed stream, and a reception method for receiving only a part of packets in the secondary multiplexed stream is provided. Also, the system clock can be reliably restored on the receiving side.

For example, OFDM (Orthogonal Frequency)
Division Multiplexing) In a broadcasting system that realizes partial reception in which only a part of a band signal in one broadcasting frequency channel can be extracted and received in a digital broadcasting that employs a modulation system, etc. There is a case where only a part of the TS packet is decoded. Even in the case of such partial reception, in the present invention,
The PCR can be reliably included in the extracted part of the TS packet, and the receiving side can reliably restore the system clock.

[Brief description of the drawings]

FIG. 1 is a block diagram of a multiplexing system according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an example in which a packet to which a PCR relating to each primary multiplexed stream is assigned is arranged in a secondary multiplexed stream at predetermined packet periods.

FIG. 3 is a diagram for explaining a setting method of a selection pattern.

FIG. 4 is a diagram for describing an example of the arrangement of packets to which PCRs have been added.

FIG. 5 is a diagram for explaining secondary multiplexing jitter.

FIG. 6 is a diagram illustrating 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 PCRs are assigned are arranged at regular time intervals.

FIG. 8 is a diagram illustrating an example of deleting a NULL packet from a primary multiplexed stream.

FIG. 9 is a block diagram of a multiplexing system according to a second embodiment of the present invention.

FIG. 10 is a diagram for explaining a PCR rewriting process.

FIG. 11 is a block diagram of a broadcasting system for transmitting 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, which are transport streams defined by ISO 33818-1.

FIG. 13 is a diagram illustrating a data structure of a TS packet defined by ISO33818-1.

FIG. 14 is a diagram for explaining a decoder model of the broadcast 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 that occurs 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 Application Laid-Open No. 11-235082.

FIG. 18 is a diagram for describing partial reception adopted in ISDB-T.

[Explanation of symbols]

1,30 multiplexing system, 11 first-order multiplexer, 1
2,32 secondary multiplexer, 13,33 receiving unit, 14,
34 secondary selection unit, 15, 35 system controller, 16, 36 separation unit, 17 PCR correction unit, 18,
39 intermediate memory, 19, 40 TSP generator, 20,
41 Primary selection unit, 37 PCR deletion unit, 38 PCR
Generator

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 5C059 MA00 RB02 RB10 RC02 RC03 RC07 RE01 RE04 SS02 UA02 UA05 UA10 UA34 5C063 AB03 AB07 AC01 AC05 5K028 EE03 EE07 KK32

Claims (40)

[Claims] 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 reference value indicating an output timing of the bit stream is included in the bit stream. A digital signal multiplexer that receives from one or more primary multiplexing devices and multiplexes the received respective multiplexed streams in packet units in a time-division manner to generate a secondary multiplexed stream. A receiving means for receiving each primary multiplexed stream, and separating each primary multiplexed stream received by the receiving means into a packet with a time reference value and a packet without a time reference value. The packet to which the time reference value is assigned and the packet to which the time reference value is not assigned. A secondary multiplexing unit that multiplexes a packet and one or more primary multiplexed streams to generate a secondary multiplexed stream that is multiplexed in packet units. The secondary multiplexing unit includes: A digital signal multiplexing apparatus, wherein a packet to which a time reference value relating to a primary multiplexed stream is assigned is arranged in a secondary multiplexed stream every predetermined packet period. 2. A time base reference value correction for correcting a time base reference value included in each primary multiplexed stream to a value synchronized with an output timing of the packet when multiplexed as a secondary multiplexed stream. 2. The digital signal multiplexing device according to claim 1, further comprising means. 3. The apparatus according to claim 1, wherein the separation unit receives, from each of the first-order multiplexing devices, a first-order multiplexed stream in which packets to which a time reference value is assigned are arranged for each predetermined number of packets. 3. The digital signal multiplexer according to 2. 4. The apparatus according to claim 1, wherein the separation unit receives, from each of the first-order multiplexing devices, a first-order multiplexed stream in which packets to which a time reference value is assigned are arranged at predetermined output time intervals. Item 3. A digital signal multiplexing device according to Item 2. 5. A reference clock for operating said digital signal multiplexing device operates asynchronously with a reference clock for operating said primary multiplexing device, and said secondary multiplexing means outputs said time reference. When the time reference value corrected by the value correction means is earlier than the time reference value added to the primary multiplexed stream by a predetermined time or more, dummy data is included in the secondary multiplexed stream. The digital signal multiplexer according to claim 2, wherein 6. The output bit rate of the secondary multiplexed stream is controlled to be higher than the sum of the bit rates allocated to each primary multiplexed stream for the secondary multiplexed output. The digital signal multiplexer according to claim 5, wherein 7. The receiving means according to claim 1, wherein the minimum value of the rating of the reference clock for operating the digital signal multiplexer is CrMIN, and the maximum value of the rating of the reference clock for operating the primary multiplexer is CpMAX. When the bit rate assigned to each degree-multiplexed stream is P, each degree-multiplexed stream whose bit rate is set to (CrMIN / CpMAX) × P is received from each degree-multiplexing apparatus. The digital signal multiplexing device according to claim 6, wherein 8. A reference clock for operating said digital signal multiplexing device operates asynchronously with a reference clock for operating said primary multiplexing device, and said secondary multiplexing means outputs said time reference. If the time reference value corrected by the value correction unit is later than the time reference value added to the primary multiplexed stream by a certain time or more, the dummy data included in the primary multiplexed stream is deleted. 3. The digital signal multiplexer according to claim 2, wherein: 9. The output bit rate of the secondary multiplexed stream is controlled to be lower than the total bit rate assigned to each primary multiplexed stream for the secondary multiplexed output. The digital signal multiplexer according to claim 8, wherein 10. The receiving means according to claim 1, wherein the minimum value of the rating of the reference clock for operating the digital signal multiplexer is CrMIN, and the maximum value of the rating of the reference clock for operating the primary multiplexer is CpMAX. When the bit rate assigned to each primary multiplexed stream is P, each primary multiplexed stream whose bit rate is set to (CpMAX / CrMIN) × P is received from each primary multiplexing device. The digital signal multiplexer according to claim 9, wherein 11. The digital signal multiplexing apparatus according to claim 8, wherein said receiving means receives a primary multiplexed stream in which dummy data is multiplexed from each of the primary multiplexing apparatuses. 12. The digital signal multiplexer according to claim 2, wherein the first-order multiplexed stream and the second-order multiplexed stream are transport streams defined in ISO / IEC13818-1. 13. The time reference value may be an ISO / IE
PCR (Program C
lock reference).
A digital signal multiplexing device according to claim 1. 14. The dummy data is an ISO / IEC
13. A NULL transport stream packet defined in 13818-1.
3. The digital signal multiplexer according to 2. 15. A time reference reference removing means for removing a time reference reference from a packet to which the separated time reference reference is attached, and a time reference reference included in the primary multiplexed stream. 2. A time reference reference value generation means for obtaining a time reference reference value corresponding to the secondary multiplexed stream based on the time reference reference value, and generating a new packet to which the calculated time reference reference value is added. Digital signal multiplexer. 16. The apparatus according to claim 1, wherein the correction means replaces the time reference value of the packet to which the separated time reference value is assigned with dummy data.
6. The digital signal multiplexer according to claim 5. 17. A reference clock for operating the digital signal multiplexing device operates asynchronously with a reference clock for operating the primary multiplexing device, and a bit rate of an output secondary multiplexed stream is as follows. , The sum of the bit rates assigned to each primary multiplexed stream for the secondary multiplexed output and the bit rate corresponding to the new packet to which the time reference value can be added. 16. The method according to claim 15, wherein
A digital signal multiplexing device according to claim 1. 18. The digital signal multiplexer according to claim 15, wherein the first-order multiplexed stream and the second-order multiplexed stream are transport streams defined in ISO / IEC13818-1. 19. The time reference value may be an ISO / IE
PCR (Program C
lock reference).
A digital signal multiplexing device according to claim 1. 20. The time reference value removing means replaces the PCR_Flag of the packet to which the PCR is assigned with 0, and sets the Stuffoff having a data length equal to the PCR.
2. The method according to claim 1, further comprising inserting an ing_byte to remove a time reference value from the primary multiplexed stream.
10. The digital signal multiplexer according to claim 9. 21. A bit stream of a digital signal is multiplexed in a time division manner on a packet basis, and one or more primary multiplexed streams including a time reference value indicating an output timing of the bit stream in the bit stream are provided. In a digital signal multiplexing method for receiving and receiving each received multiplexed stream in a time division manner on a packet basis to generate a secondary multiplexed stream, receiving each primary multiplexed stream and receiving each received primary multiplexed stream The packetized stream is separated into a packet to which a time reference value is assigned and a packet to which no time reference value is assigned, and a packet to which a time reference value is assigned and a packet to which a time reference value is assigned. And one or more primary multiplexed streams are multiplexed in packet units. When the secondary multiplexed stream is generated and the secondary multiplexed stream is multiplexed, the packets to which the time reference reference values for the respective primary multiplexed streams have been added are subjected to the secondary multiplexed stream every predetermined packet period. A digital signal multiplexing method, wherein the digital signal is multiplexed. 22. The method according to claim 11, wherein the time reference value included in each primary multiplex stream is corrected to a value synchronized with the output timing of the packet when multiplexed as a secondary multiplex stream. The digital signal multiplexing method according to claim 21. 23. The digital signal multiplexing method according to claim 22, further comprising receiving a first-order multiplexed stream in which the packets to which the time reference value is added are arranged every predetermined number of packets. 24. The digital signal multiplexing method according to claim 22, wherein a packet to which a time reference value is assigned receives a primary multiplexed stream arranged at predetermined output time intervals. 25. A reference clock used for generating a secondary multiplexed stream operates asynchronously with a reference clock used for generating the primary multiplexed stream, and the corrected time reference value is used for the primary multiplexed stream. 23. The digital signal multiplexing method according to claim 22, wherein the dummy data is included in the secondary multiplexed stream when the time becomes earlier than the time reference value added to the coded stream by a predetermined time or more. 26. The output bit rate of the secondary multiplexed stream is controlled to be higher than the sum of the bit rates allocated to each primary multiplexed stream for the secondary multiplexed output. The digital signal multiplexing method according to claim 25, wherein 27. The minimum value of the rating of the reference clock used to generate the secondary multiplexed stream is CrMI
N, when the maximum value of the rated reference clock used to generate the primary multiplexed stream is CpMBX and the bit rate assigned to each primary multiplexed stream is P, the bit rate is (CrMIN / CpMBX) × P 27. The digital signal multiplexing method according to claim 26, wherein each of the first-order multiplexed streams set in (1) is received. 28. A reference clock used to generate a secondary multiplexed stream operates asynchronously with a reference clock used to generate the primary multiplexed stream, and the corrected time reference value is used to generate the primary multiplexed stream. 23. The digital signal multiplexing method according to claim 22, wherein the dummy data included in the primary multiplexed stream is deleted when the time becomes later than a time reference value added to the multiplexed stream by a predetermined time or more. Method. 29. The bit rate of the output secondary multiplexed stream is greater than the sum of the bit rates assigned to each primary multiplexed stream for the secondary multiplexed output.
29. The digital signal multiplexing method according to claim 28, wherein the method is controlled to be low. 30. A minimum value of a rating of a reference clock used to generate the secondary multiplexed stream is CrMI.
N, when the maximum value of the rated reference clock used to generate the primary multiplexed stream is CpMBX and the bit rate assigned to each primary multiplexed stream is P, the bit rate is (CpMBX / CrMIN) × P 30. The digital signal multiplexing method according to claim 29, wherein each of the first-order multiplexed streams set in (1) is received. 31. The digital signal multiplexing method according to claim 28, wherein a first-order multiplexed stream in which dummy data is multiplexed is received. 32. The digital signal multiplexing method according to claim 22, wherein the first-order multiplexed stream and the second-order multiplexed stream are transport streams defined in ISO / IEC13818-1. 33. The time-based reference value is an ISO / IE
PCR (Program C
lock reference).
The digital signal multiplexing method according to claim 1. 34. The method according to claim 34, wherein the dummy data is an ISO / IEC
13. A NULL transport stream packet defined in 13818-1.
3. The digital signal multiplexing method according to 2. 35. A time-based reference value is removed from a packet to which a separated time-based reference value is added, and the packet is converted to a secondary multiplexed stream based on the time-based reference value included in the primary multiplexed stream. 22. The digital signal multiplexing method according to claim 21, wherein a corresponding time reference value is obtained, and a new packet to which the obtained time reference value is added is generated. 36. The digital signal multiplexing method according to claim 35, wherein the time reference reference value of the packet to which the above separated time reference reference value is assigned is replaced with dummy data. 37. A reference clock used to generate the secondary multiplexed stream operates asynchronously with the reference clock used to generate the primary multiplexed stream, and outputs a bit rate of the secondary multiplexed stream. Is the sum of the bit rates assigned to each primary multiplexed stream for the secondary multiplexed output and the bit rate for the new packet equivalent to which the time-based reference value could be added, 36. The method of claim 35, wherein
The digital signal multiplexing method according to claim 1. 38. The digital signal multiplexing method according to claim 35, wherein the first-order multiplexed stream and the second-order multiplexed stream are transport streams specified in ISO / IEC13818-1. 39. The time reference value may be an ISO / IE
PCR (Program C
lock reference).
The digital signal multiplexing method according to claim 1. 40. The method according to claim 40, wherein PCR_Flag of the packet to which the PCR is added is replaced with 0, and a Stuffing_byte having a data length equal to the PCR is inserted to remove a time reference value from the primary multiplexed stream. Item 40. The digital signal multiplexing method according to Item 39.