JP3698406B2 - Data multiplex transmission method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to transmission / reception of compressed moving image signals, so-called video compressed data and compressed audio signals, so-called audio compressed data, private data, and NULL (nonsense) data. It is about improvement.
[0002]
[Prior art]
In recent years, image processing technology, particularly compression technology for image information and audio information, has made remarkable progress, and it has become possible to transmit high-quality moving images and audio even with a transmission path having a small capacity.
The transmission mode of data and clock between the transmission side and the reception side required in such a transmission system is the serial data transmission, and in particular, the timing of S / P conversion of the initial processing on the reception side (converted from serial to parallel). In general, the sync timing (sync-byte: “47h”) included in the header information in the transport stream (hereinafter referred to as TS) is used as a reference.
However, the “47h” value is not a unique code, and the “47h” value in serial data, so-called “01000111”, exists innumerably in the TS, and the following problems occur.
[0003]
First, the basic configuration of such a transmission system is shown in FIG. 2 and described.
The transmission system in FIG. 2 includes a camera 1, a microphone 2, a TS creation unit 4, a transmission path 7, a TS analysis unit 10, a monitor 13, and a speaker 14.
When the TS creation unit 4 obtains a video image captured by the camera 1, that is, a so-called video signal 3, the video compression device 4a compresses the video signal 3 to obtain compressed video data.
On the other hand, when a sound recorded by the microphone 2, a so-called audio signal 5, is obtained, it is compressed by the audio compression device 4 b to obtain audio compressed data.
The multiplexing device 4c includes a TS packet (hereinafter referred to as a control information TS packet) including control information 17 set by the control device 16, and a TS packet (hereinafter referred to as a payload) of video compressed data by adding header information. , A video TS packet), a TS packet with audio compressed data with header information added as a payload (hereinafter referred to as an audio TS packet), and a TS packet with NULL (insignificant) data as a payload (hereinafter referred to as an audio TS packet). , Referred to as a NULL_TS packet) is time-division packet multiplexed to generate a serial TS 6 synchronized with the serial transmission clock (CK) 9 on the transmission side and output it to the transmission path 7.
The transmission path 7 performs transmission in such a manner that the serial TS 6 is taken from the transmission side and the serial TS 8 is output to the reception side. The serial transmission clock (CK) 9 on the transmission side is the same as the serial transmission clock (CK) 15 on the reception side.
When the TS analysis unit 10 obtains the serial TS 8 and the receiving-side serial transmission clock 15, the separation / splitting device 10c converts the serial TS 8 into a serial / parallel (S / P) based on a sync byte (Sync-byte: “47h”). Conversion and parallelization, and then video compression data and audio compression in which header information is removed from the multiplexed packet based on header information in the control information TS packet and video TS packet in TS and header information in audio TS packet Separate and split data.
The video expansion device 10a converts the separated and compressed video compression data into a video signal 11, and the audio expansion device 10b converts the separated and divided audio compression data into an audio signal 12, which is output and reproduced on a monitor and a speaker. .
[0004]
Next, a specific configuration and operation of the TS creation unit 4 will be described with reference to FIG.
The TS creation unit 4 includes a video compression unit 4-1, an audio compression unit 4-2, an STC counter 4-3, a system CK (clock) generator 4-4, a video PES packetization unit 4-5, and a video time stamp calculation. Unit 4-6, audio PES packetization unit 4-7, audio time stamp calculation unit 4-8, latch 4-9, FIFO memory 4-10 to 4-13, PCR encoding unit 4-14, TS packet multiplexing control 4-15, TS header storage ROM 4-16, multiple schedule data storage ROM 4-17, control information storage memory 4-18, parallel clock conversion unit 4-19, P / S conversion unit 4-20, NULL packet output unit 4 -21.
The system CK400 is supplied to the video compression unit 4-1, the audio compression unit 4-2, and the STC counter 4-3. For example, the frequency is 27 MHz.
The write side of the FIFO memories 4-10 to 4-13, the latch 4-9, and the PCR encoder 4-14 receive signals related to the system CK400 from the read side of the FIFO memories 4-10 to 4-13, In the latch 4-9, the NULL packet output unit 4-21, the TS header storage ROM 4-16, and the multiple schedule data storage ROM 4-17, signals related to the parallel clock 435 parallelized by the parallel clock conversion unit 4-19 are received. Supplied.
[0005]
Next, the detailed operation of the TS creation unit 4 will be described.
The video compression unit 4-1 and the audio compression unit 4-2 convert the video signal 3 and the audio signal 5 into video compression data 401 and audio compression data 402, respectively, according to the system CK 400.
The video PES packetizing unit 4-5 and the audio PES packetizing unit 4-7 respectively add header information to the video compressed data 401 and the audio compressed data 402 obtained from the video compressing unit 4-1 and the audio compressing unit 4-2. In addition, each packet is made into a PES packet. Then, the PES packetized video compressed data (hereinafter referred to as video PES packet data) 404 and the PES packetized audio compressed data 409 (hereinafter referred to as audio PES packet data) are written by write signals 405 and 410, respectively. , Write to FIFO memories 4-10 and 4-12, respectively. Here, PES is an abbreviation for Packetized Elementary Stream, which is a packet obtained by adding header information to compressed data.
Further, a signal 406 indicating the end of the video PES packet data, that is, the so-called end of the packet, and a signal 411 indicating the end of the audio PES packet data, that is, the so-called end of the packet, are respectively converted into the video time stamp calculation unit 4-6 and the audio time stamp calculation. Output to section 4-8.
The video time stamp calculation unit 4-6 detects header information serving as a reference for video time stamp calculation from the compressed video data 401, and at the same time holds the output of the STC counter 4-3, that is, the STC counter value 403.
Then, an offset value is added to the held STC counter value to obtain a video time stamp value 407, and a write signal 408 is generated by a signal 406 indicating the end of the PES packet data from the video PES packetizer 4-5. The video time stamp value 407 is written into the FIFO memory 4-11. In other words, when one PES packet data is stored in the FIFO memory 4-10, the video time stamp value 407 is written in the FIFO memory 4-11, and the above operation is repeated.
The audio time stamp calculation unit 4-8 detects a header serving as a reference for the audio time stamp calculation from the audio compression data 402, and simultaneously holds the output of the STC counter 4-3 at this time, that is, the STC counter value 403. Then, an offset or the like is added to the held STC counter value to obtain an audio time stamp value 412, and a write signal 413 is generated by a signal 411 indicating the end of the PES packet from the audio PES packetizing unit 4-7, and the audio The time stamp 412 is written into the FIFO memory 4-13. In other words, when one PES packet data is stored in the FIFO memory 4-12, the audio time stamp value 112 is written in the FIFO memory 4-14, and the above operation is repeated.
[0006]
Next, the multiplexing operation will be described.
The TS packet multiplexing control unit 4-15 outputs the address 427 to the TS header storage ROM 4-16 according to the multiplexing schedule data 430 obtained by outputting the address 429 to the multiplexing schedule data storage ROM 4-17.
Further, the TS packet multiplexing control unit 4-15 includes header information 428 obtained from the TS header storage ROM 4-16 and video PES packet data read from the FIFO memories 4-10, 4-11, 4-12, 4-13. 416, the video time stamp value 418, the audio PES packet data 421, the audio time stamp value 423, and the STC counter value 414 held in the latch 4-9 by the control signal 415 from the TS packet multiplexing control unit 4-15 are PCR-coded. The control information signal 432 from the control information storage memory 4-18 for storing the control information 17 set by the control device 16 (not shown), and the TS packet multiplexing control unit 4- The NULL packet read by the control signal 434 from 15 Tsu to door multiplexing.
The time division packet multiplexed data is serialized by the P / S converter 4-20, and TS6 is generated and output. Here, PCR is an abbreviation for Program Clock Reference, and is an encoded STC counter value.
[0007]
Next, reading of the FIFO memories 4-10 to 4-13 of the TS creation unit 4 will be described.
The TS packet multiplexing control unit 4-15 constantly monitors the empty flag 419 of the FIFO memory 4-11, the video PES packet data for one PES packet is accumulated in the FIFO memory 4-10, and the FIFO memory 4-11 stores the video PES packet data. When the video time stamp value 407 is written and the empty flag 419 is cleared, a read signal 420 related to the multiple schedule data 430 obtained from the multiple schedule data storage ROM 4-17 is generated, and the video time stamp value 418 is read. Subsequently, the video PES packet data 416 is read from the FIFO memory 4-10 by a read signal 417.
Also, the TS packet multiplexing control unit constantly monitors the empty flag 424 of the FIFO memory 4-13, the audio PES packet data for one PES packet is accumulated in the FIFO memory 4-12, and the audio time is stored in the FIFO memory 4-13. When the stamp value 412 is written and the empty flag 424 is released, a read signal 425 related to the multiplex schedule data 430 obtained from the multiplex schedule data storage ROM 4-17 is generated, and the audio time stamp value 423 is read, followed by the read signal. At 422, the audio PES packet data 421 is read from the FIFO memory 4-12.
If the empty flag has not been canceled, the control signal 434 is output to the NULL packet output unit 4-21, so that a meaningless NULL_TS packet is output. Here, since the empty state depends on the burst property of the compressed data written in the FIFO memory, transmission and multiplexing of NULL_TS packets are discrete.
The above operation is repeated, and video PES packet data, audio PES packet data, control information, and NULL data are converted into TS packets (188-byte units), and time-division multiplexed to generate and output serial TS6.
[0008]
Here, the control information TS packet will be briefly described.
Typical control information TS packets include a PAT (Program Association Table) packet and a PMT (Program Map Table) packet.
Here, in the PAT packet, a PID (Program ID) value of the PMT packet, a so-called PMT packet identification number (for example, “0x20”, “0x30”) is described.
The PMT packet includes a PID value (for example, “0x50”, “0x80”) of the video TS packet, a PID value of the audio TS packet (for example, “0x60”, “0x90”), and a PID value ( For example, “0x70”, “0xA0”) is described.
For example, the control information TS packet is most commonly transmitted at a rate of at least once / 100 msec. Further, the control information TS packet is transmitted at a rate of at least once / 100 ms regardless of whether or not the content of the control information is changed.
As basic processing on the receiver side, first, a PID value (for example, “0x00”) of a predetermined PAT packet is found from the received TS, and the PMT packet is determined from control information described in the PAT packet. A PID value is acquired and a PMT packet is extracted. Next, the PID value of each TS packet is acquired from the control information described in the PMT packet, each TS packet of the acquired PID value is extracted, and each compressed data is further extracted from these TS packets. Is divided and output to a decoder, which is decompressed and reproduced by the decoder.
[0009]
Next, S / P (serial / parallel) conversion and sync lock operation on the receiving side will be described with reference to FIG.
(1) When the serial TS8 is obtained on the receiving side, first, S / P conversion is performed with reference to the "47h" value (01000111) on the serial data.
{Circle around (2)} After S / P conversion, it is detected whether the “47h” value has arrived after one PES packet (188 bytes).
(3) If the “47h” value has not reached, the S / P conversion reference “47h” is not a normal sync-byte, so the S / P conversion is performed again. Repeat the above operation.
Since the “47h” value (01000111) is not a unique code, it also exists in other data such as video, audio, and private data.
Therefore, when the S / P conversion is performed based on the “47h” value that is not the sync byte, the above operation is repeated, and it is difficult to determine the maximum time until the sync clock.
[0010]
Next, the TS analysis unit 10 will be described with reference to FIG.
The TS analysis unit 10 includes a PAT packet extraction unit 10-1, a PMT packet extraction unit 10-2, a memory 10-3, a CPU 10-4, a video TS packet extraction unit 10-5, an audio TS packet extraction unit 10-6, a PCR Packet extraction unit 10-7, TS packet payload extraction unit 10-8, video timestamp value extraction unit 10-9, audio TS packet payload extraction unit 10-10, audio timestamp value extraction unit 10-11, encoding unit 10 -12, FIFO memories 10-13 and 10-15, read timing adjustment units 10-14 and 10-16, latch 10-17, STC counter 10-18, video decompression unit 10-19, audio decompression unit 10-20, System CK generator 10-21 and S / P conversion sync lock unit 10-22 It is.
The PAT packet extraction unit 10-1, the PMT packet extraction unit 10-2, the video TS packet extraction unit 10-5, the audio TS packet extraction unit 10-6, and the PCR packet extraction unit 10-7 are transmitted CK15 obtained from the transmission path 7. A signal associated with is provided. The system CK 524 is supplied to the video decompression unit 10-19, the audio decompression unit 10-20, and the STC counter 10-18.
[0011]
Next, the detailed operation of the TS analysis unit 10 will be described.
Upon obtaining the serial TS 8 and serial transmission CK 15, the S / P conversion sync lock unit 10-22 performs S / P conversion based on “47h”, so-called “01000111”, and performs the sync lock operation described with reference to FIG.
When obtaining the TS8, the PAT packet extraction unit 10-1 extracts a PAT packet that is a control information TS packet in the TS8, and writes the control information 500 in the packet to the memory 10-3 with a write signal 501.
The CPU 10-4 acquires the PID value of the PMT packet from the control information written in the memory 10-3, and outputs a control signal 506 to the PMT packet extraction unit 10-2. When the PMT packet extraction unit 10-2 obtains the control signal 506, the PMT packet extraction unit 10-2 extracts a PMT packet that is a control information TS packet in TS8, and writes the control information 502 in the packet to the memory 10-3 using a write signal 503.
The CPU 10-4 acquires the PID value of the video TS packet, the PID value of the audio TS packet, and the PID value of the PCR packet from the control information written in the memory 10-3, and sends the control signal 506 to the video TS packet extraction unit 10 −5, output to the audio TS packet extraction unit 10-6 and the PCR packet extraction unit 10-7.
[0012]
When the video TS packet extraction unit 10-5 obtains the control signal 506, the video TS packet extraction unit 10-5 extracts the video TS packet in TS8 and outputs it to the TS packet payload extraction unit 10-8 and the video time stamp value extraction unit 10-9.
When the audio TS packet extraction unit 10-6 obtains the control signal 506, the audio TS packet extraction unit 10-6 extracts the audio TS packet in TS8 and outputs it to the TS packet payload extraction unit 10-10 and the audio time stamp value extraction unit 10-11.
Upon obtaining the control signal 506, the PCR packet extraction unit 10-7 extracts the PCR packet in TS8, extracts the PCR value 509 from the packet, and outputs it to the encoding unit 10-12.
When the TS packet payload extraction unit 10-8 obtains the video TS packet 507, the TS packet payload extraction unit 10-8 extracts the net compressed video data 510 from which the header information is removed from the packet, and writes it into the FIFO memory 10-13 with the write signal 511.
When the video time stamp value extraction unit 10-9 obtains the video TS packet 507, the video time stamp value extraction unit 10-9 extracts the video time stamp value 512 in the header information from the packet, and outputs the video time stamp value 512 to the read timing adjustment unit 10-14. 513 is output to the latch 10-17.
[0013]
When the TS packet payload extraction unit 10-10 obtains the audio TS packet 508, the TS packet payload extraction unit 10-10 extracts the net audio compression data 514 from which the header information is removed from the packet, and writes it in the FIFO memory 10-15 with the write signal 516.
When the audio time stamp value extraction unit 10-11 obtains the audio TS packet 508, the audio time stamp value extraction unit 10-11 extracts the audio time stamp value 514 included in the header information from the packet, outputs the audio time stamp value 514 to the read timing adjustment unit 10-16, and outputs the control signal 513. Output to the latch 10-17.
When the encoding unit 10-12 obtains the PCR value 509, it encodes it and loads the counter value 518 into the STC counter 10-18 with the load signal 519. The STC counter 9-14 starts counting from the loaded value. Thereafter, by comparing the PCR value 509 periodically transmitted from the transmission side with the STC counter value on the reception side at the time of transmission, so-called system CK synchronization between the transmission side and the reception side is realized. .
[0014]
The read timing adjustment unit 10-14 counts down from the input video time stamp value 512 to the value of the signal 515 from the latch 10-17 on the basis of the 90 KHz clock. When the values match, the read timing adjustment unit 10-14 outputs the FIFO memory read signal 521. The data is output to the FIFO memory 10-13. This is a so-called video time stamp operation.
The read timing adjustment unit 10-16 counts down from the input audio time stamp value 517 to the value of the signal 515 from the latch 10-17 on the basis of the 90 KHz clock, and when the values match, outputs the FIFO memory read signal 523. The data is output to the FIFO memory 10-15. This is a so-called audio time stamp operation.
The video decompression unit 10-19 decompresses the input video compression data 520, and outputs and reproduces the video signal 11 on the monitor.
The audio decompression unit 10-20 decompresses the obtained audio compression data 522, and outputs and reproduces the audio signal 12 on the speaker.
By the way, as described above, the value “47h” is not a unique code but also exists in compressed data and private data, and there are many “47h” (01000111) in the serial TS. Therefore, it is difficult to specify the time until the Sync lock is performed because the operation described with reference to FIG. 4 is repeated. However, the value of the payload of the NULL_TS packet is not particularly specified, and the transmission frequency of the NULL_TS packet having NULL data as the payload is not specified.
[0015]
[Problems to be solved by the invention]
In the system of the prior art, the timing of the S / P conversion performed at the first stage of the TS analysis unit 10 on the receiving side is based on the “47h” value (01000111) of the serial TS, but the 47h value in the serial TS, so-called ( [01000111) also exist in video and audio compressed data.
Therefore, when the S / P conversion based on the sync byte is not performed, the S / P conversion is repeated again, and the time until the normal S / P conversion is completed cannot be predicted.
Therefore, the activation time or recovery time on the receiving side cannot be predicted, which is disadvantageous in systems and applications that place importance on activation and recovery times.
The present invention eliminates these drawbacks and fixes the maximum time until the completion of the S / P conversion to clarify the start-up and return time on the receiving side, and is effective for the system and application. And
[0016]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a data transmission system for transmitting a transport stream (TS) in which at least video compression data and audio compression data are used as payloads, and header information is added to each and time division packet multiplexed. A packet including NULL (meaningless) data is time-division packet multiplexed and transmitted to the TS at a predetermined cycle.
Also, in a data transmission system that transmits a transport stream (TS) in which at least video compression data and audio compression data are used as payloads, and header information is added to each of them and time-division packet multiplexed, a predetermined sync is added to the payload portion on the transmission side. A packet containing NULL (meaningless) data having no byte (Sync # byte: “47h”) value is time-division-packet-multiplexed to the TS at a predetermined cycle and transmitted from the TS received on the receiving side. A serial / parallel (S / P) conversion is performed with a predetermined sync byte value as a reference, and a sync clock process is performed to determine whether the predetermined sync byte value can be detected in the predetermined cycle. is there.
As a result, on the receiving side, S / P conversion is performed based on a predetermined sync byte value from the received TS, and when the predetermined sync byte value cannot be detected at a predetermined cycle, the S / P conversion is repeated. Since NULL packets in which “47h” does not exist in the payload are periodically multiplexed, S / P conversion can always be performed on the basis of a predetermined sync byte after this NULL packet. The maximum time required for the lock process can be fixed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIG. Here, the point that the present invention is different from the above-described system in the prior art is that a NULL_TS packet is generated and output in a packet multiplexing manner periodically rather than discretely on the transmission side.
Here, the S / P (Serial / Parallel) conversion of the S / P conversion Sync lock unit 10-22 (see FIG. 5) of the TS analysis unit 10 on the receiving side when NULL data is periodically packet-multiplexed according to FIG. The sync lock operation will be described.
{Circle around (4)} First, when the serial TS 8 is obtained on the receiving side as in the prior art, first, S / P conversion is performed with reference to the “47h” value (01000111) on the serial data.
(5) Then, after S / P conversion, it is detected whether the value “47h” has arrived after 1 PES packet (188 bytes). If the value has not been reached, the standard “01000111” is not a sync byte. Therefore, S / P conversion is performed again.
{Circle over (6)} Since “47h”, which is the reference for S / P conversion when performing S / P conversion again, does not exist in the NULL_TS packet, the next S / P next to the NULL_TS packet inserted periodically. The standard for conversion is always the sync byte position (S / P conversion (6) in FIG. 1), and normal S / P conversion can be performed. Therefore, the Sync lock is performed.
[0018]
Next, the time until the normal S / P conversion in the present invention is completed will be specifically calculated.
For example, assuming that the transmission rate of the serial TS is 8 Mbps, the rate of the parallel TS is 1/8 and thus becomes 1 Mbps.
Here, the time of one TS packet is 188 μsec, and if a NULL_TS packet is multiplexed once every 50 TS packets, the time of 50 TS packets is 9.4 msec.
Therefore, S / P conversion based on the normal sync byte can be performed within 9.4 msec at the maximum.
As described above, if a NULL_TS packet is multiplexed at a rate of once per 50 TS packets, the activation and recovery time on the receiving side should be within 9.4 msec + alpha (processing time other than S / P conversion). Is possible.
[0019]
【The invention's effect】
As described above, according to the present invention, the transmission side generates and transmits a serial TS in which a NULL_TS packet having NULL data as a payload and having a payload of NULL data is multiplexed in a predetermined cycle. It is possible to determine the maximum time required for the sync-clock processing in the data multiplex transmission system, and it is possible to deal with a system and an application that place importance on start-up and return time.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a sync lock operation on the receiving side of the present invention;
FIG. 2 is a block diagram showing the overall configuration of a general data multiplex transmission system
FIG. 3 is a block diagram showing a configuration of a transmission side of a general data multiplex transmission system.
FIG. 4 is a schematic diagram for explaining a conventional sync lock operation on the receiving side.
FIG. 5 is a block diagram showing a configuration of a receiving side of a general data multiplex transmission system.
[Explanation of symbols]
4: TS creation unit, 5, 8: Serial transport stream (TS), 7: Transmission unit, 10: TS analysis unit, 10-22: S / P conversion sync lock unit

Claims (1)

And a payload of at least video compressed data and compressed audio data, the data multiplex transmission system for transmitting a transport stream obtained by multiplexing time-division packet by adding header information predetermined sync byte (sync_byte) value respectively is present, the transmission side Then, a packet including NULL data, which is meaningless data having no predetermined sync byte (Sync_byte) value in the payload part, is time-division-packet-multiplexed and transmitted to the transport stream at a predetermined cycle. If serial / parallel conversion is performed on the basis of the predetermined sync byte (Sync_byte) value from the received transport stream , and the predetermined sync byte (Sync_byte) value cannot be detected in a predetermined packet cycle, at least the predetermined cycle The sync byte inserted in sync_by te) Data multiplexing characterized in that sync- clock processing is performed on the basis of a predetermined sync byte (Sync_byte) value existing in the header information of a packet next to a packet including NULL data which is meaningless data having no value Transmission method .

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