JP2007288604A - System and method for transmitting video - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video transmission system in which use of a reference frame including an error by packet loss is avoided when omission of packets occurs during transmission. <P>SOLUTION: A video transmitter 10 of the video transmission system divides into unit of packet, encoded data obtained by encoding a video frame and transmits the divided encoded data, wherein a video encoding part 100 which encodes a video frame to be transmitted includes an encoding control part 310 which prohibits use of a reference frame including an error part corresponding to a packet in which omission is detected according to error position information indicating an error position on the frame caused by the packet omission during transmission. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to a video transmission system that packetizes and transmits video encoded data, and more particularly, to a recovery technique for video quality degradation caused by packet loss.

  In a normal video monitoring system, an analog video signal captured by a monitoring camera is transmitted as it is, and a video is displayed on the screen of a television (TV) monitor, thereby enabling monitoring work.

  By the way, as a result of an increase in the capacity and wide area of communication networks, video transmission in which video encoded data obtained by digitally encoding analog video signals (hereinafter simply referred to as encoding) is packetized and transmitted over the network. The system is being generalized. In addition to digital television broadcasting, such a system is being applied to the above-described video surveillance system that performs video surveillance using a surveillance camera installed in a remote place, for example.

  In such a video transmission system, if a packet loss occurs during transmission, the playback video quality deteriorates when the video signal is played back on the receiving side. Normally, in order to recover the deterioration of the reproduced video quality due to the occurrence of packet loss, intra-frame encoded data called an intra-encoded frame (for example, I block or I picture in the MPEG system) is required. However, due to the recent pursuit of coding efficiency, the transmission interval of intra-coded frames, which is a recovery point for deterioration, has increased, and it takes time to recover.

  Conventionally, a system has been proposed in which when a packet is lost, a request for retransmission of the lost packet is made from the reception side to the transmission side (see, for example, Patent Documents 1 and 2). In such a system, it is possible to recover the degradation of the reproduced video quality by retransmitting the missing packet. However, the video display is stopped for the waiting time until the retransmission packet arrives. For this reason, on the receiving side, the transmitted encoded data must be buffered to some extent, so that a delay occurs in video reproduction. In addition, by transmitting a retransmission packet, it consumes network bandwidth and causes further packet loss.

  Therefore, when a packet loss is detected, the display position on the screen when it is assumed that the corresponding packet data has been reproduced is specified, and only the display position of the subsequent frame and the surrounding area are encoded as intra blocks on the transmission side. It is conceivable to use a method for transmission. With this method, it is possible to shorten the time required to recover the quality degradation of the reproduced video.

By the way, on the receiving side that decodes encoded data, when a screen (frame) including an error due to packet loss is used as a reference frame for inter-frame prediction, there is a problem that it is not possible to avoid a situation in which the error propagates over a long period of time. is there. In particular, in recent years, ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) H.264. The video coding system based on the H.264 / AVC standard has attracted attention, and the video coding system based on this standard has increased the degree of freedom in selecting a reference frame (see, for example, Non-Patent Document 1).
JP 11-331839 A JP 2000-341252 A Revised version H.264 / AVC textbook, Impress, Inc., issued January 1, 2006 (especially, see page 82, Fig. 4-1)

  As described above, when a packet loss occurs during transmission, on the receiving side that decodes encoded data, a screen (frame) containing an error due to packet loss can be used as a reference frame for interframe prediction. There is sex. In particular, H.C. In the video coding system according to the H.264 / AVC standard, there is an increased possibility that a screen including an error will be used as a reference frame for a long period of time compared to the conventional MPEG (Moving Picture coding Expert Group) 2, 4 standard, etc. Have been doing.

  Accordingly, an object of the present invention is to provide a video transmission system capable of avoiding the use of a reference frame including an error due to packet loss when a packet loss occurs during transmission.

  A video transmission system according to an aspect of the present invention is a video transmission device of a video transmission system that transmits encoded data obtained by encoding a video frame in units of packets, and encodes a video frame to be transmitted. According to the video encoding means and the packet loss information indicating the packet lost during transmission, the encoded data included in the packet is a reference frame code used as a predicted image in decoding other encoded data. Determining means for determining whether or not the encoded data is included, and when the determination result of the determining means is the encoded data of the reference frame and the encoded data included in the packet in which the loss is detected is reproduced Means for outputting the error position information indicating the position on the screen and indicating the position as an error position; storage means for storing the error position information; According to the error location information, a configuration in which a control means for prohibiting the use of a reference frame including an error portion corresponding to the missing is detected packets.

  According to the present invention, it is possible to provide a video transmission system that can avoid the use of a reference frame including an error due to a packet loss when a packet loss occurs during transmission. Accordingly, it is possible to prevent long-term propagation of errors due to packet loss.

  Embodiments of the present invention will be described below with reference to the drawings.

[Configuration of video transmission system]
FIG. 1 is a block diagram illustrating a configuration of a video transmission system according to the present embodiment.

  As shown in FIG. 1, the system is roughly divided into a video transmission unit 10, a video reception unit 20, and a network 30 that is a transmission medium.

  The video transmission unit 10 includes a video encoding unit 100 that encodes a video signal 110 including a plurality of video frames input from the video input device 11, a video packet transmission unit 101, a packet information table 102, and packet loss information. The receiving unit 103 and the comparison error position detecting unit 104 are included. The video frame is simply referred to as a frame.

  The video input device 11 is a video shooting camera such as a surveillance camera. The video encoding unit 100 is an H.264 based on the ITU-T organization. The video signal 110 is encoded in units of slices obtained by dividing a frame in accordance with a video encoding method according to the H.264 / AVC standard.

  The video packet transmission unit 101 converts video encoded data (hereinafter simply referred to as encoded data) 111 encoded by the video encoding unit 100 in units of slices into a transmission signal in units of packets, and receives video through the network 30. To the unit 20. The video packet transmission unit 101 uses UDP (User Datagram Protocol) that does not cause retransmission of data due to an error as a transport layer protocol for video packet transmission. The video encoding unit 100 outputs the encoded data 111 to the video packet transmission unit 101 and records packet information described later in the packet information table 102.

  As shown in FIG. 2, the packet information table 102 is a table for recording packet information related to an encoding mode and a position on the screen, which will be described later, in addition to the sequence number and time stamp included in the header of the transmitted packet. . In the packet information table 102, old recording data that has become unnecessary is sequentially overwritten and erased. The packet information table 102 has a table size determined by the network transmission delay and the processing time of the comparison error position detection unit 104.

  Here, the information regarding the position on the screen (the position on the screen) is information indicating a reproduction position that means a position or a range on the display screen when the video reception unit 20 reproduces the video encoded data. . Further, in the video encoding unit 100, video encoding is performed in units of blocks obtained by dividing the screen into squares, and is transmitted in order from the upper left position on the screen to the lower right position. For this reason, in the packet information table 102, the position on the screen consisting of the start block and the end block for each packet is recorded.

  The packetization is performed according to, for example, RFC (Request for Comments) 3984 of IETF (Internet Engineering Task Force). For this reason, encoded data of a plurality of frames (screens) is not included in the same packet. In other words, each packet consists only of partially encoded data in one frame.

  The video receiving unit 20 includes a video packet receiving unit 200, a video decoding unit 201, a packet loss detection unit 202, and a packet loss information transmission unit 203.

  The video packet receiving unit 200 receives the packet transmitted from the video transmitting unit 10, extracts a payload (encoded data that is video content) from the packet, and outputs the payload to the video decoding unit 201. The video decoding unit 201 is an H.264 decoder. The encoded data is decoded in accordance with the H.264 / AVC standard and output to the video output device 21. The video output device 21 includes a video monitor that reproduces the decoded video signal and displays it on the display screen.

  The video packet receiver 200 transfers the received packet header to the packet loss detector 202. As shown in FIG. 3, the packet header has a format defined by, for example, RFC (Request for Comments) 3550 standard of Internet Engineering Task Force (IETF).

  Here, sequence numbers are consecutively assigned for each packet. The time stamp is time information of the frame. Packets having the same time stamp are generated by dividing the same frame. Specifically, as shown in FIG. 2, for example, packets with sequence numbers 0123 and 0124 each have encoded data having different positions on the screen in the same frame.

  The packet loss detection unit 202 extracts a sequence number from the transferred header, and determines that a packet is missing when the sequence number is discontinuous. Specifically, for example, when the header of sequence number 0125 is input next to sequence number 0123, packet loss detection section 202 determines that the packet having the header of sequence number 0124 has been lost.

  When the packet loss detection unit 202 detects a packet loss, the packet loss detection unit 202 outputs the detection result to the packet loss information transmission unit 203. The packet loss information transmission unit 203 transmits information corresponding to the detection result to the packet loss information reception unit 103 of the video transmission unit 10 through the network 30. The packet loss information transmission unit 203 transmits, as transmission information, packet loss information including the sequence numbers and time stamps of the previous and subsequent lost packets.

  In the video transmission unit 10, the packet loss information reception unit 103 transfers the received packet loss information to the comparison error position detection unit 104. The comparison error position detection unit 104 compares the packet information recorded in the packet information table 102 at the time of transmission with the received packet loss information, and the encoded data included in the packet missing due to the error is reproduced. Specify the position on the screen (the playback range on the screen). The comparison error position detection unit 104 outputs error position information indicating the specified on-screen position to the video encoding unit 100.

  When the comparison error position detection unit 104 is encoded data of a reference frame used (referenced) as a predicted image in decoding of another slice (encoded data) as an encoding mode of a lost packet, The error position information is output to the video encoding unit 100. That is, the comparison error position detection unit 104 does not output error position information when the coding mode of the lost packet is not the coded data of the reference frame.

  Here, the I slice is encoded data within a frame that can be decoded without referring to another frame as a predicted image.

  As will be described later, the video encoding unit 100 encodes a portion (position on the screen) specified by the error position information from the comparison error position detection unit 104 in a reference frame to be transmitted next (hereinafter referred to as a part). (In some cases, it is referred to as intra coding). In addition, since motion compensation is performed, it is preferable that the peripheral portion that is the motion vector range is also a target of partial intra coding.

  Frames subjected to partial intra coding are limited to frames that can be reference images. In the case of an IDR frame in which the entire frame is intra-coded and the previous reference frame is cleared after the error position information is sent, the error position information is ignored.

[Configuration of video encoding unit]
FIG. 5 is a block diagram illustrating a configuration of the video encoding unit 100 according to the present embodiment.

  The video coding unit 100 includes a transform quantization unit 301, an entropy coding unit 302, an inverse quantization / inverse transform unit 303, a deblocking filter 304, a reference frame memory 305, and a coding mode switching unit 306. , An intra-screen prediction unit 307, a motion compensation unit 308, a motion detection unit 309, an encoding control unit 310, an output buffer 311, and an error position memory 312.

  The video encoding unit 100 according to this embodiment is an H.264 standard. This is a method to which a video encoding method according to the H.264 / AVC standard is applied. The motion compensation unit 308 estimates a motion from a reference frame selected from a plurality of reference frames stored in the reference frame memory 305 and creates a prediction signal. That is, the motion compensation unit 308 creates an inter-frame prediction screen from the reference frame based on the motion vector detected from the video signal 110 by the motion detection unit 309.

  The transform quantization unit 301 performs DCT (Discrete Cosine Transform) quantization on the residual signal between the video signal 110 (video to be encoded) and the prediction signal. The entropy encoding unit 302 performs variable length encoding processing on the signal subjected to DCT quantization by the transform quantization unit 301, and stores the encoded data in the output buffer 311. The video packet transmission unit 101 converts the frame-unit encoded data (video encoded data) 111 stored in the output buffer 311 into a packet-unit transmission signal, and transmits the packet-based transmission signal to the video reception unit 20 through the network 30. . The in-screen (intra) prediction unit 307 predicts an image sample at another position from the signal subjected to DCT quantization by the transform quantization unit 301 using the image sample in the same screen.

  Further, the inverse quantization / inverse transform unit 303 performs the inverse process of the transform quantization unit 301. Further, the deblocking filter 304 is a filter for reducing distortion generated at the block boundary during encoding.

  Along with the function processing units as described above, the video encoding unit 100 of the present embodiment includes an encoding control unit 310 having a function of selecting the encoding type by controlling the overall control and encoding mode switching unit 306, and An error position memory 312 is included.

  The encoding control unit 310 stores the error position information output from the comparison error position detection unit 104 in the error position memory 312. Furthermore, the encoding control unit 310 outputs control information 400 for controlling the encoding mode switching unit 306 based on the error position information. Also, the encoding control unit 310 outputs information 410 for selecting a reference frame from a plurality of reference frames stored in the reference frame memory 305. Further, as will be described later, the encoding control unit 310 instructs the video reception unit 20 to delete the reference frame including the error from the reference frame memory in order to prohibit the use of the reference frame including the error. 420 is output.

[Function and effect]
Hereinafter, with reference to FIG. 4 to FIG. 8, the operational effects relating to the system of the present embodiment will be described.

  First, in the video transmission unit 10, the video encoding unit 100 encodes the video signal 110 input from the video input device 11 that is a surveillance camera, for example, in units of slices obtained by dividing a frame (screen). Is generated. The video packet transmission unit 101 converts the encoded data 111 into transmission data in units of packets and transmits the transmission data to the video reception unit 20 through the network 30.

  The video receiver 20 decodes the encoded data included in the received packet into a video signal and outputs it to the video output device 21. The video output device 21 reproduces the decoded video signal and displays it on the display screen of the video monitor.

  Here, as shown in the flowchart of FIG. 7, in the video reception unit 20, when the packet loss detection unit 202 detects a missing packet from a series of received packets, the packet loss information transmission unit 203 displays the packet loss information as video. It transmits to the packet loss information receiving part 103 of the transmission part 10 (YES of step S1).

  When receiving the packet loss information, the packet loss information receiving unit 103 outputs the packet loss information to the comparison error position detecting unit 104 (step S2). The comparison error position detection unit 104 compares the packet loss information with the packet information recorded in the packet information table 102 at the time of transmission, and identifies a packet lost due to an error.

  Further, the comparison error position detection unit 104 specifies the position on the screen (reproduction range on the screen) of the packet missing from the packet information table 102 (step S3). Here, the comparison error position detection unit 104 determines whether or not the encoded data is a reference frame based on the encoding mode of the packet lost due to the error (step S4). When the determination result is not a reference frame, the comparison error position detection unit 104 is encoded data that is not referred to as a predicted image in the decoding of another frame, and thus does not execute the error recovery process in this embodiment. (NO in step S4).

  On the other hand, if the encoding mode of the missing packet is a reference frame, the comparison error position detection unit 104 outputs error position information indicating the specified on-screen position to the video encoding unit 100 (step S5).

  FIG. 4 is a diagram for explaining a state when a packet loss (packet loss) occurs. That is, when, for example, two packets are lost from a reference frame being transmitted, as shown in FIG. 4, in the decoding of a slice that refers to the reference frame as a predicted image, quality degradation of the reproduced video occurs.

  Since the system of the present embodiment has a function of transmitting a partial video corresponding to a missing packet in a frame to be transmitted thereafter by partial intra coding, error recovery can be realized (see step S12 in FIG. 8). As a result, the quality of the reproduced video can be recovered by decoding the slice that refers to the error-recovered frame as the predicted image.

  By the way, H.C. applied to the system of this embodiment. In the video encoding system according to the H.264 / AVC standard, a reference frame can be freely selected when a slice is encoded. For this reason, as shown in FIG. 6, a frame 62 to be decoded is generated with reference to a frame 60 including an error before the frame 61 after the frame 61 error-recovered by the partial intra coding. To do. Since the frame 62 refers to the frame 60 including an error (packet missing), the quality of the reproduced video is deteriorated. Furthermore, if the frame 62 to be decoded is a reference frame, it may be used as a reference frame when decoding subsequent frames 63 and 64. In FIG. 6, a time Td means a delay time associated with transmission of packet loss information and error position identification processing.

  In short, H. In the video encoding method based on the H.264 / AVC standard, when a reference frame 60 including an error due to a packet loss during transmission occurs, the reference frame 60 may be used in the video receiving unit 20 for a long period of time. In other words, there is a possibility that long-term propagation of errors due to packet loss occurs.

  Therefore, the video encoding unit 100 according to the present embodiment executes the following countermeasures for errors due to packet loss during transmission.

  In the video encoding unit 100, as shown in FIG. 5, when a packet loss occurs during transmission, the encoding control unit 310 stores the error position information output from the comparison error position detection unit 104 in the error position memory 312. To do. As described above, the error position information is information indicating a position on the screen when the missing packet is a reference frame and the missing portion is reproduced.

  In order to prohibit the use of a reference frame including an error, the encoding control unit 310 outputs a command 420 for deleting the reference frame including the error from the reference frame memory to the video reception unit 20. The command 420 is transmitted to the video packet receiving unit 200 by the video packet transmitting unit 101 and given to the video decoding unit 201.

  In the video decoding unit 201, when an error occurs in a reference frame that is referenced for a long period of time, a reference frame that is not used is accumulated in the reference frame memory. For this reason, since the normal reference frame is not used effectively, the reproduction image quality of the decoded video is deteriorated. To cope with this, the video decoding unit 201 can delete the reference frame having an error from the reference frame memory by transmitting the command 420 from the encoding control unit 310, and the normal stored in the reference frame memory. Effective reference frame can be used.

  Further, the encoding control unit 310 executes error recovery processing in the procedure as shown in the flowchart of FIG.

  In a normal encoding process, the encoding control unit 310 outputs information 410 for selecting a reference frame based on a preset rule or high encoding efficiency and stores it in the reference frame memory 305. A reference frame is selected from the plurality of reference frames. The video encoding unit 100 performs an encoding process in units of slices on the video signal 110 using the selected reference frame as a predicted image.

  Here, when the video encoding unit 100 selects to use a reference frame including the error in a situation where an error has occurred in the reference frame in the video decoding unit 201 due to occurrence of packet loss, As described above, the quality of the reproduced video deteriorates.

  Therefore, the encoding control unit 310 according to the present embodiment executes a special encoding process for error recovery when a situation in which a reference frame including an error is expected. That is, the encoding control unit 310 determines whether or not a reference frame including an error exists among the plurality of reference frames stored in the reference frame memory 305 (step S10). When there is a reference frame including an error, the encoding control unit 310 determines whether there is a normal reference frame that is not used in the reference frame memory 305 (step S11).

When there is no normal reference frame that is not used, the encoding control unit 310 outputs the control information 400 to control the encoding mode switching unit 306, and operates the in-screen prediction unit 307,
In accordance with the error position information, a partial intra encoding process is performed for intra (in-plane) encoding the video portion of the error occurrence position and its peripheral part only (step S12). In other words, the video transmission unit 10 transmits the partial video corresponding to the missing packet in the P frame to be transmitted thereafter by performing partial intra encoding and transmits the P frame from which the error has been recovered (61 in FIG. 6). See).

  On the other hand, when there is a normal reference frame that is not used, the encoding control unit 310 performs a temporary encoding process on the video signal 110 using the normal reference frame, and includes an error. The frame is changed to a non-existing frame (step S13). However, if it is not a reference frame that is close in time, the generated code amount may increase and the expected compression rate and video reproduction quality may not be obtained. In such a case, the encoding control unit 310 controls the encoding mode switching unit 306 to operate the intra prediction unit 307 and executes the partial intra encoding process (NO in step S14, S12). .

  The encoding control unit 310 performs a temporary encoding process using the normal reference frame, and performs an error recovery process that adopts the result of the temporary encoding and changes the reference frame to include no error. (YES in step 14, S15).

  As described above, according to the present embodiment, when a packet loss occurs during transmission, the error position information output from the comparison error position detection unit 104 is stored in the error position memory 312. Using this error position information, it is possible to realize a control that prohibits the use of a reference frame including an error in the video decoding unit 201 (see the description of the command 420).

  Further, based on the error position information, a frame including an error-occurring part (block) is not used as a reference frame, and another normal reference frame or a frame including a partially intra-coded block is used as a reference frame. Can do. Therefore, as shown in FIG. 6, the video decoding unit 201 can perform the decoding process of the frame 62 using the error-recovered frame 61 as a reference frame.

  Accordingly, it is possible to avoid using a reference frame including an error due to occurrence of packet loss over a long period of time. It is effective for a video coding system having a high degree of freedom in selecting a reference frame, such as the H.264 / AVC standard.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope 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. Furthermore, constituent elements over different embodiments may be appropriately combined.

The block diagram which shows the structure of the video transmission system regarding embodiment of this invention. The figure which shows an example of the packet information table regarding this embodiment. The figure which shows an example of the header format of the packet regarding this embodiment. The figure for demonstrating the error recovery process regarding this embodiment. The block diagram which shows the structure of the video encoding part regarding this embodiment. The figure for demonstrating the error recovery process regarding this embodiment. The flowchart for demonstrating the procedure of the packet loss detection process regarding this embodiment. 6 is a flowchart for explaining a procedure of error recovery processing according to the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Video transmission part, 11 ... Video input device, 20 ... Video reception part, 21 ... Video output device,
30 ... Network, 100 ... Video encoder, 101 ... Video packet transmitter,
102 ... Packet information table, 103 ... Packet loss information receiver,
104: Comparison error position detection unit, 200: Video packet reception unit,
201 ... Video decoding unit, 202 ... Packet loss detection unit,
203 ... packet loss information transmission unit, 301 ... transform quantization unit,
302 ... Entropy encoding unit, 303 ... Inverse quantization / inverse transform unit,
304: Deblocking filter, 305: Reference frame memory,
306 ... Coding mode switching unit, 307 ... In-screen prediction unit, 308 ... Motion compensation unit,
309 ... Motion detection unit, 310 ... Coding control unit, 311 ... Output buffer,
312: Error position memory.

Claims (9)

A video transmission device of a video transmission system for transmitting encoded data obtained by encoding a video frame by dividing it into packet units,
Video encoding means for encoding a video frame to be transmitted;
Whether the encoded data included in the packet is encoded data of a reference frame used as a prediction image in decoding of other encoded data according to packet loss information indicating a packet lost during transmission Determination means for determining whether or not
When the determination result of the determination unit is the encoded data of the reference frame, the position on the screen when the encoded data included in the packet in which the loss is detected is reproduced is specified, and the position is determined as the error position. Means for outputting error position information indicated as:
Storage means for storing the error position information;
A video transmission apparatus comprising: control means for prohibiting use of a reference frame including an error portion corresponding to the packet in which the loss is detected according to the error position information. The control means includes
A video decoding device that receives and decodes encoded data in units of packets is prohibited from using a reference frame in which encoded data corresponding to the position on the screen specified by the error position information is missing. The video transmission apparatus according to claim 1, wherein an instruction to perform the instruction is issued.   When there is a reference frame in which the encoded data at the error position is missing, the encoded data at the error position is recovered by using a normal reference frame including normal encoded data corresponding to the error position. The video transmission device according to claim 1, further comprising error recovery means for executing an error recovery process. The error recovery means includes
4. If the normal reference frame does not exist, the encoded data at the error position is recovered by encoding partial video data corresponding to the error position into intra-frame encoded data. The video transmission device described in 1.   When there is a reference frame in which the encoded data at the error position is missing, the encoded data at the error position is encoded with partial video data corresponding to the error position into intra-frame encoded data, and the error 3. The video transmission apparatus according to claim 1, further comprising error recovery means for executing an error recovery process for recovering the encoded data of the position. A video transmission method applied to a video transmission system that transmits encoded data obtained by encoding a video frame in units of packets,
Detecting a missing packet when encoding and transmitting a video frame to be transmitted; and
Whether or not the encoded data included in the packet is encoded data of a reference frame used as a prediction image in decoding of other encoded data according to packet loss information indicating the lost packet. A determining step;
When the determination result of the determination unit is the encoded data of the reference frame, the position on the screen when the encoded data included in the packet in which the loss is detected is reproduced is specified, and the position is determined as the error position. And outputting error position information indicated as
A video transmission method, comprising: prohibiting use of a reference frame including an error portion corresponding to a packet in which the loss is detected according to the error position information.   A video decoding device that receives and decodes encoded data in units of packets is prohibited from using a reference frame in which encoded data corresponding to the position on the screen specified by the error position information is missing. The video transmission method according to claim 6, wherein an instruction is given.   When there is a reference frame in which the encoded data at the error position is missing, the encoded data at the error position is recovered by using a normal reference frame including normal encoded data corresponding to the error position. The video transmission method according to claim 6, wherein error recovery processing is executed.   9. The encoded data at the error position is recovered by encoding the partial video data corresponding to the error position into intra-frame encoded data when the normal reference frame does not exist. The video transmission method described in 1.

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