JP4035802B2 - Packet generating apparatus, packet reproducing apparatus and methods thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a packet generation device, a packet reproduction device, and a method thereof, and is suitably applied to, for example, a packet generation device and a packet reproduction device used for digital television broadcasting.
[0002]
[Prior art]
Conventionally, digital satellite broadcasting that digitizes a video signal and broadcasts it via a satellite has been started. In such digital satellite broadcast, a plurality of video signals are compressed and encoded using a moving picture experts group (MPEG) 2 system on the transmission side, and then multiplexed and transmitted. On the receiving side, the received broadcast wave is decoded and displayed using the MPEG2 system.
[0003]
FIG. 8 shows a digital satellite broadcasting system 1 as a whole, and encoding units 5A to 5C having the same configuration compress video signals and audio signals supplied from the outside using an MPEG (Moving Picture Experts Group) 2 system. These are encoded and output to the multiplexing device 9 as bit streams S5A to S5C in which PES (Packetized Elementary Stream) packets having a predetermined packet length are continuous.
[0004]
Multiplexing buffers 11A to 11C included in the multiplexing device 9 receive and temporarily store bit streams S5A to S5C, respectively. The selection unit 8 switches and reads the bit streams S5A to S5C stored in the multiplex buffers 11A to 11C at a predetermined timing, thereby transporting each PES packet constituting the bit streams S5A to S5C with a length of 188 bytes. Are then multiplexed and output to the error correction code adding unit 30 as a transport stream S9 composed of continuous transport packets.
[0005]
The error correction code adding unit 30 adds a predetermined error correction code to the transport stream S9 and outputs it to the modulation unit 40. The modulation unit 40 modulates the transport stream S9 with a predetermined modulation method, and transmits it to the satellite 50 via the transmission antenna 41 as a broadcast signal S3. The satellite 50 receives and amplifies the broadcast signal S3, and retransmits it as the broadcast signal S4.
[0006]
An IRD (Integrated Receiver Decorder: reception decoding device) 60 receives the broadcast signal S4 via the reception antenna 42, demodulates the broadcast signal S4, and then decodes the video signal S64 and the audio signal S65 using the MPEG2 system. And output to the television receiver 100. The television receiver 100 displays the video signal S64 and reproduces the audio signal S65 with a speaker (not shown).
[0007]
In such a multiplexing apparatus, when a PES packet is divided into transport packets, a process called alignment is performed to adjust the position of the PES header so that it is located immediately after the TP (Transport Packet) header.
[0008]
FIG. 9 shows an alignment process, in which a certain transport packet TP1 includes the tail part D1 of the PES packet data, and the data length of the tail part D1 of the PES packet data is less than the payload length Lp of the transport packet TP1. , Invalid data (hereinafter referred to as dummy data Ddum) is added between the TP header Htp and the tail portion D1 of the PES packet data, and the PES header Hp is added as it is after the TP header Ht in the subsequent transport packet TP1. To do. By performing such alignment processing, the PES header Hpes is not divided between the two transport packets TP1 and TP1, and there is an advantage that the PES header can be easily separated from the transport stream during decoding.
[0009]
FIG. 10 shows buffer occupancy transitions of the bit streams S5A to S5C in the multiplex buffers 11A to 11C (FIG. 7), the horizontal axis indicates time, and the vertical axis indicates the occupancy of each buffer in units of transport packets. .
[0010]
When data is always input to each of the multiplex buffers 11A to 11C at a constant rate, a bit stream equivalent to 1/3 of the transport packet is accumulated in each of the multiplex buffers 11A to 11C for each time slot. From each multiplex buffer, data for one transport packet is read out at a rate of once every three time slots. Here, the solid line indicates the occupation amount SA of the multiplex buffer 11A, and the multiplex buffer 11A reads the bit stream S5A at the timing of the time slots A1 to An. Similarly, the broken line indicates the occupation amount SB of the multiplex buffer 11B, and the multiplex buffer 11B reads the bit stream S5B at the timing of the time slots B1 to Bn. The dotted line indicates the occupation amount SC of the multiplex buffer 11C, and the multiplex buffer 11C reads the bit stream S5C at the timing of the time slots C1 to Cn.
[0011]
[Problems to be solved by the invention]
Here, the alignment processing is performed on the bit stream S5C in the time slot C2 shown in FIG. 10, so that only a part of the data that is originally read is read from the multiplexing buffer 11C. The buffer occupation amount of the bit stream S5C in the buffer 11C is increasing. Such alignment processing occurs once for each PES packet, and in extreme cases, only one byte may be read in one time slot.
[0012]
In this way, the amount of bit stream read from the multiplex buffer is reduced by performing alignment processing, a delay occurs in the multiplex buffer, and packetization efficiency is reduced by adding dummy data to the transport packet. Has the problem.
[0013]
The present invention has been made in view of the above points, and intends to propose a packet generation apparatus and a packet reproduction apparatus that improve packetization efficiency and a method thereof with a simple configuration.
[0014]
[Means for Solving the Problems]
  In order to solve this problem, the present invention provides a predetermined packet length.With a header at the beginningA packet length shorter than the first packet from the data string in which the first packets are continuous.With a header at the beginningGenerate second packetIn digital television broadcasting systemsIn the packet generation device, the first packet constituting the data string is divided into second packets.The second2 packet includes the tail part of the first packet, and the data length of the second packetPayload excluding headerIf less than the lengthInAnd the first packet that followsFrom the header of the first packetPacket division adding means for adding to the tail part of the first packet to the second packetheaderIs includedIn,That the header of the first packet is included in the second packet and the headerIndicates the position ofheaderAdd location information to a predetermined area of the second packetheaderAnd position information adding means.
[0015]
  The second packet includes the tail part of the first packet, andData length isConcernedOf the second packetPayload excluding headerIf less than the lengthInDivide the following first packetAt the tailBy adding, it is possible to avoid adding dummy data to the second packet and improve packetization efficiency.In addition, header information indicating that the header of the first packet is included in the second packet and header position information indicating the position of the header are added to a predetermined area of the second packet including the header of the first packet. Thus, even when the header of the first packet is divided, the first packet can be easily reproduced on the reproduction side.
[0016]
  In the present invention,Predetermined packet lengthWith a header at the beginningA data string consisting of consecutive first packets is represented by a packet length shorter than that of the first packet.It has a header at the beginning generated by dividing byInput a second packet and reproduce the first packet based on the second packetIn digital television broadcasting systemsIn the packet reproduction device, the first packetheaderAdded to a predetermined area of the second packet includingThat the header of the first packet is included in the second packet and that the headerIndicate positionheaderBased on location informationThe header of the first packet included in the second packetAnalyzing positionheaderBased on the position analysis means and the analysis result, the first packet is reproduced from the second packet.When playing back the contents of the header of the first packetAnd packet reproducing means.
[0017]
  Contains the header of the first packetAppended to the second packet,A header indicating that the header of the first packet is included in the second packet and the position of the headerBy referring to location information,Even if the header of the first packet is splitThe first packet can be easily reproduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0019]
In FIG. 1, in which parts corresponding to those in FIG. 8 are assigned the same reference numerals, 2 denotes a digital satellite broadcasting system as a whole, and encoding units 5A to 5C having the same configuration are respectively supplied with video signals and audio supplied from outside. The signal is compressed and encoded by the Moving Picture Experts Group (MPEG) 2 method, and the PES (Packetized Elementary Stream) packet as the first packet is continuously formed into bit streams S5A to S5C to the multiplexing device 10 as the packet generation device. Output.
[0020]
FIG. 2 shows the multiplexing apparatus 10 as a whole, and the multiplexing buffers 11A to 11C receive and temporarily store the bit streams S5A to S5C, respectively. At this time, the header analysis unit 12 constantly monitors the bit streams S5A to S5C, detects the position of the PES header included in each PES packet constituting the bit streams S5A to S5C, and uses the position information of the PES header as the header position. The information S12 is output to a TP (Transport Packet) header generating unit 13 as a head position information adding unit and a PTS / DTS (Presentation Time Stamp / Decoding Time Stamp: display time information / decoding time information) changing unit 19.
[0021]
An SI (System Information) control unit 15 generates an SI packet multiplexing request signal S15 based on a multiplexing interval when an SI packet, which is a packet indicating multiplexing information of the transport stream, is multiplexed on the transport stream. This is output to the channel selection control unit 21, and the SI packet S 16 stored in the SI packet file 16 is read out and output to the channel selection unit 17 as packet dividing means.
[0022]
The channel selection control unit 21 always monitors the occupation amount of the bit stream in the multiplex buffers 11A to 11C as the buffer occupancy information S11, and the channel selection signal S21 based on the buffer occupancy information S11 and the SI packet multiplex request signal S15. Is output to the channel selector 17.
[0023]
The channel selection unit 17 operates in accordance with the channel selection signal S21, thereby transferring data supplied from the NULL packet generation unit 14, the TP header generation unit 13, the multiple buffers 11A to 11C, and the SI packet file 16 in units of transport packets. Multiplex. That is, the channel selection unit 17 divides the bit streams S5A to S5C supplied from the multiplexing buffers 11A to 11C as the payload of the transport packet and adds the TP header S13 supplied from the TP header generation unit 13 to the leading end of the payload. The transport packet is generated, and the transport packet, the NULL packet S14 supplied from the NULL packet generator 14 and the SI packet S16 supplied from the SI packet file 16 are multiplexed, and the transport as a second packet A transport stream S10 composed of continuous packets is generated and output. The NULL packet S14 is a packet of invalid data inserted when there is no input of the bit streams S5A to S5C.
[0024]
Here, the channel selection control unit 21 does not perform alignment processing on the PES header, and generates a transport packet by adding the PES header of the next PES packet following the end of the PES packet data. That is, as shown in FIG. 3, when a certain transport packet TP1 includes the tail portion D1 of the PES packet data, and the data length of the tail portion D1 of the PES packet data is less than the payload length Lp of the transport packet TP1 The dummy data is not added to the tail portion D1 of the PES packet data, but the PES header Hpes1 of the subsequent PES packet is divided to generate a divided PES header Hpes1, and this is added to the tail portion D1 of the PES packet data. Then, in the next transport packet TP2, the remaining divided PES header Hpes2 is added to the TP header Htp to generate a transport packet.
[0025]
At this time, information indicating the position of the PES header in the transport packet is written in the transport packet including the PES header. That is, as shown in FIG. 4, the adaptation field in the transport packet includes an area called a private data area that can be freely used by the user. The TP header generation unit 13 (FIG. 2) calculates the data length from the tail of the TP header to the beginning of the PES header based on the header position information S12 supplied from the header analysis unit 12, and calculates the value of this data length. The private data area is entered as an 8-byte length pointer field Pf, and the value of the TP private data length Tpr is entered as “1” indicating that the PES header is included in the transport packet. The pointer field is not entered in the TP header of the transport packet that does not include the PES header, and the value of the TP private data length Tpr is entered as “0”.
[0026]
Thus, the channel selection unit 17 multiplexes the bit streams S5A to S5C supplied from the multiplexing buffers 11A to 11C without performing alignment processing on the PES header, and temporarily stores them in the multiplexing register 18 as the transport stream S10.
[0027]
FIG. 5 shows the buffer occupancy transition of the bit streams S5A to S5C in the multiplex buffers 11A to 11C (FIG. 2). The horizontal axis represents time, and the ordinate represents the bit stream occupancy of each of the multiplex buffers 11A to 11C. Shown in packets. When the bit streams S5A to S5C are input at a fixed same rate, each of the multiple buffers 11A to 11C stores bit streams S5A to S5C in an amount corresponding to 1/3 of the transport packet for each time slot. At the same time, the bit streams S5A to S5C for one transport packet are read from each of the multiplexing buffers 11A to 11C once every three time slots. Here, the solid line indicates the occupation amount SA of the multiplex buffer 11A, and the multiplex buffer 11A reads the bit stream S5A at the timing of the time slots A1 to An. Similarly, the broken line indicates the occupation amount SB of the multiplex buffer 11B, and the multiplex buffer 11B reads the bit stream S5B at the timing of the time slots B1 to Bn. The dotted line indicates the occupation amount SC of the multiplex buffer 11C, and the multiplex buffer 11C reads the bit stream S5C at the timing of the time slots C1 to Cn. Since the multiplexing apparatus 10 does not perform alignment processing, data for one transport packet is always read from each of the multiplexing buffers 11A to 11C.
[0028]
The PTS / DTS rewriting unit 19 (FIG. 2) responds to the multiplexing information S22 supplied from the channel selection control unit 21 and the header position information S12 supplied from the header analysis unit 12, and the transformer stored in the multiplexing register 18. The values of PTS and DTS of the port stream S17 are rewritten according to a reference time called PCR (Program Clock Reference). The CC (Continuity Counter) adding unit 20 adds a cyclic counter indicating the continuity of the transport packet to a predetermined position of each transport packet constituting the transport stream S17 stored in the multiplex register 18. To do. Then, the multiplex register 18 outputs the transport stream S10 to which the PTS and DTS are rewritten and the cyclic counter is added to the error correction code adding unit 30 (FIG. 1).
[0029]
The error correction code adding unit 30 adds a predetermined error correction code to the transport stream S10 and outputs it to the modulation unit 40. Then, the modulation unit 40 modulates the transport stream S10 with a predetermined modulation method, and transmits it to the satellite 50 via the transmission antenna 41 as a broadcast signal S3. The satellite 50 receives and amplifies the broadcast signal S3 and retransmits it as the broadcast signal S3.
[0030]
An IRD (Integrated Receiver Decorder: reception decoding apparatus) 60 receives the broadcast signal S4 via the reception antenna. FIG. 6 shows an IRD 60 as a whole, and a front end unit 61, a decryption unit 62, a separation unit 63 as a packet reproduction device, a control unit 71, an IC (Integrated Circuit) card interface 73, and a ROM (Read Only Memory) 75 are buses. 70 is connected.
[0031]
The front end unit 61 demodulates the broadcast signal S4 supplied from the receiving antenna 42 (FIG. 1) to generate a transport stream S61, and outputs this to the decryption unit 62. The descrambling unit 62 descrambles the transport stream S61 based on the descrambling information stored in the IC card 74 and the ROM 75 inserted in the IC card interface 73, and outputs it to the separating unit 63. The control unit 71 generates a channel selection signal S71 according to the channel selection input signal S76 generated when the operator operates the operation unit 76, and outputs the channel selection signal S71 to the separation unit 63 via the bus 70.
[0032]
First, the separation unit 63 separates the transport packet of the channel indicated by the channel selection signal S71 from the transport stream S61, and further reproduces the PES packet from the separated transport packet. At this time, the control unit 71 as the head position analyzing means obtains the head position information of the PES header by referring to the value of the pointer field written in the transport packet, and uses this as header position information S72 to separate the separation section 63. Output to. Based on the header position information S72, the separation unit 63 reproduces the PES packet so that the PES header is positioned at the head of the reproduced PES packet.
[0033]
Further, the separation unit 63 determines the content of the PES packet based on the PES header of the reproduced PES packet, outputs the PES packet including the video data to the video decoding unit 64 as the video bit stream S63V, and includes the audio data. The PES packet is output to the audio decoding unit 64 as an audio bitstream S63A. At this time, the separation unit 63 uses a DRAM (Dynamic Random Access Memory) 66 as a buffer.
[0034]
The video decoding unit 64 decodes the video bit stream S63V by using the MPEG2 system, and outputs it as a video signal S64 to the television receiver 100 (FIG. 1). Similarly, the audio decoding unit 65 decodes the audio bit stream S63A using the MPEG2 system and outputs the audio bit stream S63A to the television receiver 100 as an audio signal S65. At this time, the video decoding unit 64 and the audio decoding unit 65 perform the decoding process using the DRAMs 67 and 68 as buffers, respectively. The television receiver 100 displays the video signal S64 and reproduces the audio signal S65 with a speaker (not shown).
[0035]
In the above configuration, the multiplexing apparatus 10 does not perform alignment processing when multiplexing the bit streams S5A to S5C, and the transport packet including the tail part of the PES packet has the data length of the tail part of the PES packet being transported. If it is less than the payload length of the packet, the PES header of the subsequent PES packet is divided and added to generate the transport stream S10. At this time, the TP header generation unit 13 adds a pointer field indicating the head position of the PES header to the private data area of the transport packet including the head portion of the PES header.
[0036]
The modulation unit 40 modulates the transport stream S10 to generate a transmission signal S3, and transmits this to the satellite 50 via the transmission antenna 41. The IRD 60 receives the transmission signal S4 retransmitted by the satellite 50 via the reception antenna 42.
[0037]
The separation unit 63 included in the IRD 60 reproduces the PES packet from the transport stream S61 obtained by demodulating the broadcast signal S4. At this time, the control unit 71 obtains the head position information of the PES header based on the pointer field entered in the transport packet, and the separation unit 63 reproduces the contents of the PES header based on the head position information.
[0038]
According to the above configuration, when the data length of the PES packet is less than the payload length of the transport packet in the transport packet including the tail part of the PES packet, the header part of the subsequent PES packet is divided to end the PES packet. A dummy data is added to the PES packet by adding a pointer field indicating the head position of the PES packet in the transport packet to the transport packet including the head portion of the PES header and adding the tail portion to the transport packet including the head portion of the PES header. Packetization efficiency can be improved as much as it does not contain.
[0039]
Further, when the PES packet is reproduced from the transport packet in the IRD 60, the contents of the PES header can be reproduced based on the pointer field.
[0040]
In the above-described embodiment, the case where the pointer field indicating the position of the PES header in the transport packet is written in the private data area has been described. However, the present invention is not limited to this, and the pointer field is set to the private data. You may make it fill in in positions other than an area | region. For example, as shown in FIG. 6, a pointer field may be provided after the TP header, and position information indicating the position of the PES header may be added thereto.
[0041]
In the above-described embodiment, the case where the present invention is applied to a multiplexing device and a demultiplexing device in digital satellite broadcasting has been described. However, the present invention is not limited to this, and various other methods such as digital terrestrial broadcasting and digital cable broadcasting can be used. It may be applied to various broadcasting systems.
[0042]
Further, in the above-described embodiment, the case where the present invention is applied to a multiplexing apparatus that generates a transport stream by multiplexing a plurality of bit streams into transport packets has been described, but the present invention is not limited thereto, You may apply to the packetization apparatus which carries out the transport packetization of one bit stream.
[0043]
Furthermore, in the above-described embodiment, the data length from the tail end of the TP header to the head of the PES header is entered as the pointer field Pf. However, the present invention is not limited to this. What is necessary is to make it possible to determine the leading position of the PES header in the transport packet, such as the data length up to.
[0044]
【The invention's effect】
  As described above, according to the present invention,The second packet includes the tail part of the first packet, andData length isConcernedOf the second packetOf the part excluding the headerWhen the payload length is not reachedInDivide the first packet that followsBestAppend to tailBy doing so, it is possible to avoid adding dummy data to the second packet and improve the packetization efficiency. In addition, the second packet is placed in a predetermined area of the second packet including the header of the first packet. Includes a header indicating that the header of the first packet is included and the position of the headerBy adding location information,Even when the header of the first packet is divided, the first packet can be easily reproduced on the reproduction side.
[0045]
  Also,A header added to the second packet including the header of the first packet and indicating that the header of the first packet is included in the second packet and the header indicating the position of the headerBy reproducing the first packet based on the position information,Even if the header of the first packet is splitThe first packet can be easily reproduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a digital satellite broadcasting system.
FIG. 2 is a block diagram illustrating a multiplexing device according to the present invention.
FIG. 3 is a schematic diagram illustrating division of a PES packet.
FIG. 4 is a schematic diagram illustrating a structure of a transport packet.
FIG. 5 is a graph showing transition of buffer occupancy.
FIG. 6 is a block diagram showing an IRD.
FIG. 7 is a schematic diagram showing the entry position of a pointer field.
FIG. 8 is a block diagram showing a conventional digital satellite broadcasting system.
FIG. 9 is a schematic diagram illustrating alignment processing.
FIG. 10 is a graph showing buffer occupation amount transition by alignment processing;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 2 ... Digital satellite broadcasting system, 8 ... Selection part, 5A-5C ... Coding part, 9, 10 ... Multiplexer, 11A-11C ... Multiplexing buffer, 12 ... Header analysis part, 13 ...... TP header generation unit, 14 ... NULL packet generation unit, 15 ... SI control unit, 16 ... SI packet file, 17 ... channel selection unit, 18 ... multiple register, 19 ... PTS / DTS rewrite unit , 20... CC addition unit, 21... Channel selection control unit, 30... Error correction code addition unit, 40 .. modulation unit, 41... Transmission antenna, 42. ... IRD, 61 ... front end section, 62 ... decryption section, 63 ... separation section, 64 ... video decryption section, 65 ... audio decryption section, 66, 67, 68 ... DRAM, 70 ... bus , 71 …… Control unit, 73 ...... IC card interface, 74 ...... IC card, 75 ... ROM, 76 ...... operation unit.

Claims (8)

A digital packet that generates a second packet having a packet length shorter than the first packet and having a header at the head portion from a data string having a predetermined packet length and having a first packet having a header at the head portion. In a packet generation device in a television broadcasting system ,
The first packet constituting the data string is divided into the second packet, the second packet comprises the last portion of the first packet, the header data length of the second packet If less than the payload length of the portion excluding a packet dividing adding means for adding subsequent the first packet from the header of the first packet in the end portion,
If the header is included in the second packet in the first packet, the said second header position information indicating and position of the header includes a header of the second above packet of the first packet And a header position information adding means for adding to a predetermined area of the packet. The header position information, as the position of the header of the first packet, the packet generating apparatus according to claim 1, characterized in that indicating a beginning position of the header in the second packet. The second packet has a header position information addition area in which the header position information is added to the tail part of the header,
The header position information adding means adds the header position information to the header position information adding area.
The packet generation device according to claim 1. A digital packet that generates a second packet having a packet length shorter than the first packet and having a header at the head portion from a data string having a predetermined packet length and having a first packet having a header at the head portion. In a packet generation method in a television broadcasting system ,
Dividing the first packet constituting the data string into the second packet;
The second packet contains the last portion of the first packet, that if the data length is less than the payload length of the portion excluding the header of the second packet, the subsequent said first packet Append to the last part from the header of the first packet ,
If the header is included in the second packet in the first packet, the said second header position information indicating and position of the header includes a header of the second above packet of the first packet A packet generation method characterized by adding to a predetermined area of the packet. A data string in which the first packet is continuously having a header at the head portion becomes a predetermined packet length is generated by dividing a short packet length than the first packet, the head portion a second having a header In a packet reproduction device in a digital television broadcasting system , which inputs a packet and reproduces the first packet based on the second packet,
The header position information indicating that the header of the first packet is included in the second packet and the header position information indicating the position of the header is added to a predetermined area of the second packet including the header of the first packet. Based on the header position analyzing means for analyzing the position of the header of the first packet included in the second packet ,
A packet reproducing device comprising: packet reproducing means for reproducing the contents of the header of the first packet when reproducing the first packet from the second packet based on the analysis result . The header position information, said as a position of the header of the first packet, the packet reproducing apparatus according to claim 5, characterized in that indicating a beginning position of the header in the second packet. The second packet has a header position information addition area in which the header position information is added to the tail part of the header,
The header position analysis means analyzes the position of the header of the first packet included in the second packet based on the header position information added to the header position information addition area.
The packet reproduction device according to claim 5, wherein: A data string in which the first packet is continuously having a header at the head portion becomes a predetermined packet length is generated by dividing a short packet length than the first packet, the head portion a second having a header In a packet reproduction method in a digital television broadcasting system, which receives a packet and reproduces the first packet based on the second packet,
The header position information indicating that the header of the first packet is included in the second packet and the header position information indicating the position of the header is added to a predetermined area of the second packet including the header of the first packet. Based on the position of the header of the first packet included in the second packet ,
A packet reproduction method comprising: reproducing contents of a header of the first packet when reproducing the first packet from the second packet based on the analysis result.

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