JP2010245838A - Video transmission system, transmitting apparatus, receiving apparatus and hold time control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video transmission system that allows a receiving apparatus to properly correct an error even if a transmission rate of a data packet is changed by a transmitting apparatus, and to provide the transmitting apparatus, the receiving apparatus, and a hold time control method to be used in the system. <P>SOLUTION: In the transmitting apparatus 10, video data packetized by a packetizing section 11 are error-correction-coded in an error-correction coding buffer section 12 and transmitted from a transmitting section 16 to the receiving apparatus 20. In the receiving apparatus 20, an error is corrected on the video data from the transmitting apparatus 10 by error-correction buffer sections 23-1, 23-2 and the video data are output to a post-stage. A control packet generating section 13 generates control information for controlling hold time of the error-correction buffer sections 23-1, 23-2 on the basis of the time required for the error-correction coding buffer section 12 to accumulate data packets for a predetermined capacity. In accordance with the control information, a receiving control section 25 controls the hold time of the error-correction buffer sections 23-1, 23-2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a video transmission system for transmitting packetized video data via a network, and a transmission device, a reception device, and a holding time control method used in the system.

  In recent years, in the data transmission on the Internet, in addition to the download type transmission system conventionally used, the service by the stream type transmission system is increasing (for example, refer patent document 1). In this stream-type transmission system, received data can be played back while data is transferred from the transmission device to the reception device in the transmission system, so it can be used for Internet services such as Internet telephony, remote video conferencing, and video on demand. Has been.

  As an Internet technology suitable for the stream type transmission method, there is RTP (Realtime Transport Protocol) defined by IETF RFC3550. In data transfer by RTP, a time stamp is added to a packet as time information, and the time relationship between the transmission device and the reception device is grasped by this, so that it is not affected by delay fluctuation (jitter) of packet transfer. Can be played back in sync with.

  Here, RTP does not guarantee real-time data transfer. Since packet delivery priority, setting, management, and the like are not within the scope of transport services provided by RTP, RTP packets may experience delivery delay and packet loss in the same way as other packets. Even if such a situation occurs, the receiving apparatus can reproduce data using only packets that arrive within the expected time. This is because video and audio data can be reproduced to some extent even if there is some data loss.

  As a technique for improving the reliability of data transfer using RTP, there is a technique called a forward error correction coding system, a so-called FEC (Forward Error Correction) system. In this FEC scheme, redundancy coding is performed using an error correction code such as an RS (Reed-Solomon) code with a predetermined number of data packets as one unit.

  For example, when (n, k) RS code is used in the transmission apparatus, n packets obtained by adding nk redundant packets to k data packets can be transmitted to the reception apparatus. Here, n> k. The receiving apparatus holds the received packet and performs error correction every preset holding time. At this time, if a total of n packets can be received from the transmission device within this holding time, the data packet loss due to the influence of packet loss or the like is reduced by RS decoding processing using n−k redundant packets. Can be restored. However, the transmission rate of the data packet transmitted to the receiving device may be changed in the transmitting device. In such a case, since the number of data packets transmitted per unit time changes, n packets including redundant packets cannot be received, and there is a problem that error correction cannot be performed normally. It was.

JP 2004-112136 A

  As described above, in the conventional video transmission system, when the transmission rate of the data packet is changed on the transmission device side, the error correction cannot be normally performed on the reception device side.

  The present invention has been made in view of the above circumstances, and its purpose is video transmission capable of normally performing error correction on the receiving device side even when the transmission rate of the data packet is changed on the transmitting device side. A system, and a transmission device, a reception device, and a holding time control method used in the system are provided.

  In order to achieve the above object, a video transmission system according to the present invention is a video transmission system in which packetized video data is transmitted by a transmission device and a reception device, and the transmission device packetizes the video data to generate a data packet. A packetizing unit that generates the data packet and sequentially holds the generated data packet, and when the capacity of the stored data packet reaches a preset capacity, performs error correction coding on the data packet for the capacity, An encoding buffer unit that outputs the data packet for the capacity and the redundant packet generated by the error correction encoding, and the capacity of the data packet held in the encoding buffer unit reaches the preset capacity A control information generating unit that generates control information for the receiving device based on the time until A transmission unit that transmits the redundant packet and the control information to the reception device, and the reception device receives a data packet, a redundant packet, and control information transmitted from the transmission device; The received data packet and the redundant packet are temporarily held, and when a specified holding time has elapsed, the data packet held at the holding time is error-corrected using the redundant packet and then output. A buffer unit and a control unit that controls a holding time in the error correction buffer unit based on the control information.

  Further, a transmission device according to the present invention is used in a video transmission system that transmits packetized video data by a transmission device and a reception device, and a packetizing unit that packetizes the video data to generate a data packet; The generated data packets are sequentially held, and when the held data packet capacity reaches a preset capacity, error correction coding is performed on the data packet for the capacity, and the data packet for the capacity and the error An encoding buffer unit that outputs redundant packets generated by correction encoding, and the reception device based on a time until a capacity of the data packet held in the encoding buffer unit reaches the preset capacity A control information generator for generating control information for the data packet, the redundant packet, and the control information Characterized by a transmission unit that transmits to the receiving device.

  In addition, the receiving apparatus according to the present invention includes a packetizing unit that packetizes video data to generate a data packet, and sequentially holds the generated data packet, and the capacity of the stored data packet is set to a preset capacity. An encoding buffer unit that performs error correction encoding on the data packet for the capacity and outputs the data packet for the capacity and the redundant packet generated by the error correction encoding; and the encoding buffer unit A control information generating unit that generates control information based on a time until the capacity of the data packet held in the memory reaches the preset capacity, and a transmission that transmits the data packet, the redundant packet, and the control information A data packet transmitted from the transmission device, used in a video transmission system including a transmission device comprising: A receiving unit that receives a long packet and control information, and temporarily holds the received data packet and redundant packet. When a specified holding time has elapsed, the data packet held at the holding time is An error correction buffer unit that outputs after correcting an error using a packet, and a control unit that controls a holding time in the error correction buffer unit based on the control information.

  The holding time control method according to the present invention is a holding time control method used in a video transmission system for transmitting packetized video data by a transmitting device and a receiving device, and packetizing the video data to generate a data packet. The generated data packets are sequentially held in the encoding buffer unit of the receiving device, and when the capacity of the held data packets reaches a preset capacity, an error correction code is added to the data packets for the capacity. And generating control information for the receiving device based on the time until the capacity of the data packet held in the encoding buffer unit reaches the preset capacity, the data packet for the capacity, The redundant packet generated by error correction coding and the control information are transmitted from the transmitting device to the receiving device. Then, based on the control information transmitted from the transmitting device, the data packet and redundant packet holding time in the error correction buffer unit of the receiving device is controlled, and the data packet and redundant packet transmitted from the transmitting device are Temporarily held in an error correction buffer unit, and when the controlled holding time has elapsed, the data packet held in the error correction buffer unit is error-corrected using the redundant packet.

  In the video transmission system, the transmission device, the reception device, and the holding time control method configured as described above, the error correction buffer unit of the reception device is based on the time required to store a predetermined amount of data packets in the encoding buffer unit of the transmission device. The holding time is controlled. As a result, even when the transmission rate is changed by the transmission device, the retention time of the error correction buffer unit can be changed according to the change of the transmission rate.

  According to the present invention, a video transmission system capable of normally performing error correction even when the transmission rate of a data packet is changed on the transmission device side, and a transmission device and a reception device used in this system And a retention time control method can be provided.

It is a block diagram which shows the function structure of the video transmission system which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the FEC redundant encoding in the error correction encoding buffer part of FIG. It is a figure which shows the flowchart at the time of the reception control part of FIG. 1 controlling the holding time of an error correction buffer part.

  Hereinafter, embodiments of a video transmission system, a transmission device, a reception device, and a holding time control method according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a functional configuration of a video transmission system according to an embodiment of the present invention. The transmission device 10 and the reception device 20 are connected via a network, and the packetized video data transmitted from the transmission device 10 is transmitted to the reception device 20.

  The transmission apparatus 10 includes a packetization unit 11, an error correction coding buffer unit 12, a control packet generation unit 13, a switch 14, a switching control unit 15, and a transmission unit 16. The packetizing unit 11 packetizes video data compressed by MPEG4, for example, and generates a data packet. At this time, the packetizing unit 11 generates a data packet in accordance with RTP defined in IETF RFC1889.

  When the data packet generated by the packetizing unit 11 is accumulated in a predetermined capacity, the error correction coding buffer unit 12 performs FEC (forward error correction code) redundant coding on the data packet accumulated in the predetermined capacity. The data packet having a predetermined capacity and the redundant packet generated by the FEC redundant encoding are output to the switch 14.

  FIG. 2 is a schematic diagram showing an example of FEC redundant coding in the error correction coding buffer unit 12. The error correction coding buffer unit 12 is, for example, a 3 × 3 matrix buffer, and sequentially accumulates data packets supplied from the packetizing unit 11 from “1”. At this time, the error correction encoding buffer unit 12 performs redundancy encoding using erasure error correction codes such as Reed-Solomon (RS) codes, with nine data packets satisfying a predetermined capacity as one unit. Do. For example, when a (12,9) RS code is used, the error correction encoding buffer unit 12 generates three redundant packets from nine data packets before redundant encoding, and a total of 12 data packets Become. Here, in the error correction coding buffer unit 12, when the seventh data packet is accumulated, the redundant packet 1 is generated, and when the eighth data packet is accumulated, the redundant packet 2 is generated, and the ninth data packet is generated. When the packet is accumulated, the redundant packet 3 is generated. Nine data packets and three redundant packets are supplied to the switch 14 in the order shown in FIG. 2, for example.

  When a predetermined amount of data packets are stored in the error correction coding buffer unit 12, the control packet generator 13 measures the time taken to store the predetermined capacity, and calculates the transmission rate of the data packets. When the transmission rate is calculated, the control packet generator 13 generates control information based on the calculated transmission rate. The control packet generator 13 generates a control packet by packetizing the generated control information according to RTP. The generated control packet is output to the switch 14.

  The switch 14 receives the data packet and the redundant packet from the error correction coding buffer unit 12, and the control packet from the control packet generation unit 13, and either data packet according to switching control from the switching control unit 15 described later. Is selectively derived.

  The switching control unit 15 performs switching control on the switch 14. That is, when the switching control unit 15 detects that a data packet having a predetermined capacity is accumulated in the error correction coding buffer unit 12, the switching control unit 15 switches the switch 14 so as to derive the control packet from the control packet generation unit 13. When the derivation of the control packet is completed, the switching control unit 15 switches the switch 14 so as to derive the data packet and the redundant packet from the error correction coding buffer unit 12. The data packet derived from the switch 14 is supplied to the transmitter 16. The transmission unit 16 allocates the control packet, the data packet, and the redundant packet to different ports and transmits them to the reception device 20.

  The receiving device 20 includes a receiving unit 21, a switch 22, error correction buffer units 23-1 and 23-2, a timer 24, and a reception control unit 25. The reception unit 21 receives the control packet generated by the control packet generation unit 13 that is transmitted first from the transmission device 10, and outputs the control packet to the reception control unit 25. The receiving unit 21 receives the data packet and the redundant packet following the control packet, and outputs them to the switcher 22.

  The switch 22 selectively derives the data packet and the redundant packet from the receiving unit 21 to one of the error correction buffer units 23-1 and 23-2 according to switching control from the receiving control unit 25 described later. .

  The error correction buffer units 23-1 and 23-2 hold the data packet and the redundant packet derived from the switch 22, and each time the time measured by the timer 24 reaches a predetermined holding time, the held data packet Are output to the packet release units 26-1 and 26-2, respectively. At this time, the error correction buffer units 23-1 and 23-2 perform error correction on the data packet using the retained redundant packet.

  The error correction buffer units 23-1 and 23-2 are, for example, the same 3 × 3 matrix buffer as the error correction encoding buffer unit 12, and the order shown in FIG. 2 from the error correction encoding buffer unit 12. The data packets transmitted in (1) are stored sequentially from “1”. The error correction buffer units 23-1 and 23-2 store the first to seventh data packets, and when the redundant packet 1 is received next, the redundant packets 1 are used to store the first, fourth, and seventh data packets. Restore the packet. Further, when the eighth data packet is stored and the redundant packet 2 is received next, the second, fifth, and eighth data packets are restored using the redundant packet 2. Further, when the ninth data packet is accumulated and the next redundant packet 3 is received, the third, sixth, and ninth data packets are restored using the redundant packet 3. However, the error correction buffer units 23-1 and 23-2 have redundant packets 1 to 3 when a predetermined holding time has elapsed before receiving all nine data packets and all three redundant packets. Error correction based on the above cannot be performed.

  The packet release units 26-1 and 26-2 release the data packets from the error correction buffer units 23-1 and 23-2 and output them to the subsequent stage.

  The reception control unit 25 performs switching control on the switch 22. That is, while the data packet is output from the error correction buffer unit 23-1, the switch 22 is switched so that the received data packet is supplied to the error correction buffer unit 23-2, and the error correction buffer unit 23- While the data packet is output from 2, the switch 22 is switched so that the received data packet is supplied to the error correction buffer unit 23-1.

  When receiving the control packet from the receiving unit 21, the receiving control unit 25 controls the error correction buffer units 23-1 and 23-2. That is, the data packet holding time in the error correction buffer units 23-1 and 23-2 is controlled according to the control information included in the control packet.

  Next, operation in the above configuration will be described. FIG. 3 is a diagram illustrating a flowchart when the reception control unit 25 controls the holding times of the error correction buffer units 23-1 and 23-2 in the video transmission system according to the embodiment of the present invention. Here, a case where the transmission rate of data transmitted from the transmission device 10 is changed from 30 Mbps to 15 Mbps will be described as an example.

  The error correction coding buffer unit 12 retains a predetermined capacity of the data packet supplied from the packetizing unit 11 and performs redundant coding. The control packet generator 13 measures the time taken for the data packet to hold a predetermined capacity, and calculates the transmission rate (15 Mbps) from the measured time. Then, control information is generated based on the calculated transmission rate. Now, since the transmission rate of the data packet has been changed from 30 Mbps to 15 Mbps, the time required for the error correction coding buffer unit 12 to perform redundant coding takes twice as long as when it was 30 Mbps. The control packet generation unit 13 generates control information so that the holding time in the error correction buffer units 23-1 and 23-2 is twice that when the transmission rate is 30 Mbps. The transmitting apparatus 10 transmits a control packet including this control information, and then transmits a data packet for a predetermined capacity and a redundant packet generated by redundant encoding.

  First, the receiving device 20 receives a control packet from the transmitting device 10. When receiving the control packet (step 31), the reception control unit 25 sets the holding time in the error correction buffer units 23-1 and 23-2 to double the previous time based on the control information (step 32). Then, the error correction buffer units 23-1 and 23-2 hold the data packet from the transmission device 10 for the newly set holding time, perform error correction using the redundant packet, and perform the data packet after error correction. Is output to the packet release units 26-1 and 26-2.

  As described above, in the above-described embodiment, the error correction buffer unit 23-1 in the reception device 20 is based on the time taken to accumulate a predetermined amount of data packets in the error correction coding buffer unit 12 of the transmission device 10. , 23-2 are controlled. Thereby, even when the transmission rate is changed by the transmission apparatus 10, it is possible to change the holding time of the error correction buffer units 23-1 and 23-2 according to the change of the transmission rate.

  Therefore, the video transmission system according to the present invention can perform error correction normally on the receiving device 20 side even when the transmission rate of the data packet is changed on the transmitting device 10 side, and is resistant to errors. Data transmission can be performed.

  The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the example in which the control information generated by the control packet generation unit 13 is packetized according to RTP has been described. However, the method of packetizing control information is not limited to RTP. Even when packetized according to Transmission Control Protocol (UDP) or UDP (User Datagram Protocol), it can be similarly implemented.

  In the above embodiment, an example has been described in which the transmission device ** packetizes and transmits control information. However, the control information is not limited to being packetized.

  In the above embodiment, the error correction encoding buffer unit 12 and the error correction buffer units 23-1 and 23-2 are 3 × 3 matrix type buffers, but a matrix other than 3 × 3 is described. The same can be applied to the case of a buffer.

  In the above embodiment, the video data is packetized and transmitted from the transmission apparatus 10 to the reception apparatus 20. However, in addition to the video data, audio data is packetized and the transmission apparatus 10 and the reception apparatus 20 are transmitted. Even in the case of transmission between them, it can be similarly implemented.

  Furthermore, the present invention can be embodied by modifying the constituent elements without departing from the spirit of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 10 ... Transmission apparatus 11 ... Packetization part 12 ... Error correction encoding buffer part 13 ... Control packet generation part 14 ... Switch 15 ... Switching control part 16 ... Transmission part 20 ... Reception apparatus 21 ... Reception part 22 ... Switch 23- 1, 23-2 ... Error correction buffer unit 24 ... Timer 25 ... Reception control unit 26-1, 26-2 ... Packet release unit

Claims (9)

In a video transmission system for transmitting packetized video data by a transmission device and a reception device,
The transmitter is
A packetizing unit that packetizes the video data to generate a data packet;
The generated data packets are sequentially held, and when the capacity of the held data packets reaches a preset capacity, error correction coding is performed on the data packets for the capacity, and the data packets for the capacity and the data packets An encoding buffer unit for outputting redundant packets generated by error correction encoding;
A control information generating unit that generates control information for the receiving device based on a time until the capacity of the data packet held in the encoding buffer unit reaches the preset capacity;
A transmission unit for transmitting the data packet, the redundant packet, and the control information to the receiving device;
The receiving device is:
A receiving unit for receiving data packets, redundant packets and control information transmitted from the transmitting device;
Error correction that temporarily holds the received data packet and redundant packet, and when the specified holding time has elapsed, the data packet held at the holding time is error-corrected using the redundant packet and then output. A buffer section;
A video transmission system comprising: a control unit that controls a holding time in the error correction buffer unit based on the control information. The control information generation unit packetizes the generated control information to generate a control packet,
The transmitting unit transmits the data packet, the redundant packet, and the control packet to the receiving device;
The receiving unit receives the data packet, the redundant packet, and the control packet,
The video transmission system according to claim 1, wherein the control unit controls the holding time based on control information included in the control packet. The video transmission system according to claim 2, wherein the transmission unit transmits the control packet to the reception device first, and then transmits the data packet and the redundant packet to the reception device. Used in a video transmission system that transmits packetized video data by a transmission device and a reception device,
A packetizing unit that packetizes the video data to generate a data packet;
The generated data packets are sequentially held, and when the capacity of the held data packets reaches a preset capacity, error correction coding is performed on the data packets for the capacity, and the data packets for the capacity and the data packets An encoding buffer unit for outputting redundant packets generated by error correction encoding;
A control information generating unit that generates control information for the receiving device based on a time until the capacity of the data packet held in the encoding buffer unit reaches the preset capacity;
A transmission apparatus comprising: a transmission unit configured to transmit the data packet, the redundant packet, and the control information to the reception apparatus. The control information generation unit packetizes the generated control information to generate a control packet,
The transmission device according to claim 4, wherein the transmission unit transmits the data packet, the redundant packet, and the control packet to the reception device. 6. The transmission apparatus according to claim 5, wherein the transmission unit transmits the control packet to the reception apparatus first, and then transmits the data packet and the redundant packet to the reception apparatus. A packetizing unit that packetizes video data to generate a data packet, and sequentially holds the generated data packet. When the capacity of the stored data packet reaches a preset capacity, the data packet for the capacity An error correction coding, and outputs a data packet for the capacity and a redundant packet generated by the error correction coding; and a capacity of the data packet held in the coding buffer section A video comprising a transmission device comprising: a control information generation unit that generates control information based on a time until reaching the preset capacity; and a transmission unit that transmits the data packet, the redundant packet, and the control information Used in transmission systems,
A receiver that receives data packets, redundant packets, and control information transmitted from the transmitter;
The received data packet and the redundant packet are temporarily held, and when a specified holding time has elapsed, the data packet held at the holding time is error-corrected using the redundant packet and then output. A buffer section;
And a control unit that controls a retention time in the error correction buffer unit based on the control information. When the control information generation unit packetizes the generated control information to generate a control packet, and the transmission unit transmits the data packet, the redundant packet, and the control packet to the receiving device,
The receiving unit receives the data packet, the redundant packet, and the control packet,
The receiving apparatus according to claim 7, wherein the control unit controls the holding time based on control information included in the control packet. In a holding time control method used in a video transmission system for transmitting packetized video data by a transmission device and a reception device,
Packetizing the video data to generate a data packet;
The generated data packet is sequentially held in the encoding buffer unit of the receiving device,
When the capacity of the held data packet reaches a preset capacity, error correction coding is performed on the data packet for the capacity,
Generating control information for the receiving device based on a time until the capacity of the data packet held in the encoding buffer unit reaches the preset capacity;
The data packet for the capacity, the redundant packet generated by the error correction coding and the control information are transmitted from the transmitting device to the receiving device,
Based on the control information transmitted from the transmitter, control the retention time of the data packet and redundant packet in the error correction buffer unit of the receiver,
Data packets and redundant packets transmitted from the transmission device are temporarily held in the error correction buffer unit,
When the controlled holding time has elapsed, the data packet held in the error correction buffer unit is error-corrected using the redundant packet.

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