Patent Publication Number: US-8971415-B2

Title: Video communication system, device and method based on feedback reference frames

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of PCT/CN2009/074007 filed Sep. 17, 2009, which claims the priority benefit under USC 119 of CN 200810161276.2 filed Sep. 24, 2008, the entire respective disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to video communication technologies, and more particularly, to a video communication system, device and method on the basis of feedback reference frame. 
     BACKGROUND OF THE INVENTION 
     With the development of video communication technologies and the improvement of network bandwidth, more and more users adopt video communication, such as network video playing, video chat, video conference and video-on-demand. Thus, life and work of societal public have been greatly enriched. Meanwhile, further development of the video communication technologies and network technologies are accelerated. 
     However, since the instability of network bandwidth and network transmission quality easily caused by complicated architecture and “best effort” characteristics of the Internet, video communication quality of current video communication system is difficult to be guaranteed under some circumstances, which has a serious influence on users&#39; usage. One of primary bottlenecks affecting video communication quality currently is pause of video transmission caused by loss of network packets.  FIG. 1  is a brief data flow diagram illustrating existed video communication technologies, in which video encoding end encodes video frames according to predefined rules and frame type, and then sends the encoded video frames to video decoding end through a network. The video decoding end decodes received video frames, and then plays the video. 
     However, according to currently widely applied technical solution, when network packets are lost in network congestion caused by a certain reason and video decoding end cannot restore decodable data with remaining data, it is necessary for the video encoding end to encode an Intra frame (I frame) with large data amount to be sent to the video decoding end, thus, not only bandwidth resources are wasted, but also existed network congestion is further aggravated. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide a video communication system, device and method on the basis of feedback reference frame, so as to reduce data amount transmitted when frames are lost or decoding is failed in a video communication process. 
     Technical schemes provided by embodiments of the invention are implemented as follows. 
     A video communication method on the basis of feedback reference frame, which is applied in a system including a video encoding end and a video decoding end, the method including: 
     receiving, by the video encoding end, video frame information fed back by the video decoding end, determining a reference frame for encoding current video image according to the video frame information, encoding the current video image according to determined reference frame, sending a video frame formed after the encoding; 
     decoding, by the video decoding end, received video frame, and feeding back the video frame information to the video encoding end through a network according to decoding result. 
     A video communication system on the basis of feedback reference frame, in which the system includes a video encoding end, a video decoding end, a network respectively connected with the video encoding end and the video decoding end, the video encoding end at least includes a video capture module adapted to capture current video image, a video encoding module adapted to encode the current video image, and a data transmitting module adapted to send a video frame formed after encoding by the video encoding module to the video decoding end through the network, the video decoding end at least includes a video decoding module adapted to decode received video frame, the video encoding end further includes a reference frame judging module, the video decoding end further includes a feedback module; 
     the reference frame judging module is adapted to receive the video frame information fed back by the feedback module, and determine a reference frame for encoding the current video image according to the video frame information; 
     the video encoding module is adapted to encode the current video image according to the reference frame determined by the reference frame judging module; 
     the feedback module, which is connected with the video decoding module, is adapted to feed back the video frame information to the video encoding end through the network and according to decoding result of the video decoding module. 
     A video encoding communication device on the basis of feedback reference frame, which at least includes a video capture module adapted to capture current video image, a video encoding module adapted to encode the current video image, and a data transmitting module adapted to transmit a video frame formed after encoding by the video encoding module to a video decoding end through a network, the device further includes: 
     a reference frame judging module, which is located between the video capture module and the video encoding module, adapted to obtain video frame information fed back by the video decoding end, determine a reference frame used to encode the current video image according to the video frame information, and provide determined reference frame to the video encoding module which is adapted to execute encoding operations for the current video image. 
     A video decoding end device on the basis of feedback reference frame, in which the device at least includes a video decoding module adapted to decode received video frame, the device further includes: 
     a feedback module, which is connected with the video decoding module, adapted to feed back video frame information to a video encoding end through a network and according to decoding result of the video decoding module. 
     In the video communication system, device and method on the basis of feedback reference frame provided by embodiments of the invention, the feedback module at the video decoding end feeds back video frame information of the video decoding end to the video encoding end, when frames are lost or decoding is failed at the video decoding end, the video encoding end may utilize the video frame information fed back to encode an Inter frame (P frame) with high compression ratio and small data amount, and may maintain the video communication. Thus, network data flow may be reduced during the video communication process. Meanwhile, phenomenon which may cause greater impact on the network, when it is necessary to send larger data amount since frame-loss or failed-decoding, may be avoided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating structure of a system about existed video communication technologies. 
         FIG. 2   a  is a diagram illustrating basic structure of a system in accordance with an embodiment of the invention. 
         FIG. 2   b  is a diagram illustrating detailed structure of a system in accordance with an embodiment of the invention. 
         FIG. 2   c  is a diagram illustrating structure of an encoding end device in accordance with an embodiment of the invention. 
         FIG. 2   d  is a diagram illustrating structure of a reference-frame feedback module in an encoding end device in accordance with an embodiment of the invention. 
         FIG. 2   e  is a diagram illustrating structure of a decoding end device in accordance with an embodiment of the invention. 
         FIG. 3  is a schematic diagram illustrating a brief flow in accordance with an embodiment of the invention. 
         FIG. 4  is a diagram illustrating detailed flow about encoding communication in accordance with an embodiment of the invention. 
         FIG. 5  is a diagram illustrating detailed flow about decoding communication in accordance with an embodiment of the invention. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     In a video communication system on the basis of feedback reference frame provided by embodiments of the present invention, a feedback module, which is configured to feed back video frame information of video decoding end to video encoding end, is added in the video decoding end; a reference frame judging module, which is configured to receive the video frame information fed back by the feedback module, and determine a reference frame used to encode current video image according to the video frame information, is added in the video encoding end. Thus, when frames are lost or decoding is failed at the video decoding end, operations performed by the video encoding end in the prior art to encode an Intra frame (I frame) with large data amount once again and to send the I frame to the video decoding end may be avoided. Detailed descriptions will be provided in the following. 
     In order to make objectives, technical solutions and advantages of the invention clearer, detailed descriptions about the invention will be provided in the following accompanying with attached figures and specific embodiments. 
     With reference to  FIG. 2   a ,  FIG. 2   a  is a diagram illustrating basic structure of a video communication system on the basis of feedback reference frame in accordance with a first embodiment of the invention. The system includes a video encoding end  10   a , a video decoding end  20   a , and a network  30   a  which is respectively connected with video encoding end  10   a  and video decoding end  20   a . Video encoding end  10   a  includes at least a video capture module  11   a  configured to capture current video image, a video encoding module  12   a  configured to encode current video image, and a data transmitting module  13   a  configured to transmit a video frame to video decoding end through a network, in which the video frame is formed after encoding by the video encoding module. The video decoding end includes at least a video decoding module  22   a , which is configured to decode received video frames. In the embodiment of the invention, as shown in  FIG. 2   a , video encoding end  10   a  further includes a reference frame judging module  14   a , video decoding end  20   a  further includes a feedback module  24   a.    
     Reference frame judging module  14   a  receives video frame information fed back by feedback module  24   a , and determines a reference frame for encoding current video image according to the video frame information. 
     Thus, video encoding module  12   a  may encode current video image according to the reference frame determined by reference frame judging module  14   a , to form a video frame. And then, the video frame is sent to video decoding end  20   a  through network  30   a . The process of video encoding module  12   a  encoding current video image according to the reference frame determined by reference frame judging module  14   a  may be implemented as follows. Video encoding module  12   a  encodes current video image with an inter-frame encoding mode to form a video frame (specifically is an Inter frame, P frame for short). 
     Feedback module  24   a  connecting with video decoding module  22   a , is configured to feed back video frame information to video decoding end  10   a  according to decoding result of video decoding module  22   a.    
     It should be explained that, connection relationships among each device in all the figures of the invention are existed for clearly clarifying information interaction and control process, thus they should be understood as logical connection relationships, instead of limiting to physical connections. Besides, it should be explained that, both video encoding end  10   a  and video decoding end  20   a  may be client and/or server end, or software run in client and/or server end. Meanwhile, roles of them are relative, which is not confined to a fixed role. As is well known by persons having ordinary skill in the art, video encoding end  10   a  and video decoding end  20   a  include physical or logical buffer, so as to facilitate storing data necessary to be buffered, e.g., to store captured video image, video frame information, encoded video frame, decoded video frame, etc. 
     In the foregoing, descriptions about basic structure of the video communication system provided by an embodiment of the invention were provided. In the following, descriptions about detailed structure provided by an embodiment of the invention are provided. 
     With reference to  FIG. 2   b ,  FIG. 2   b  is a diagram illustrating detailed structure of a video communication system on the basis of feedback reference frame in accordance with the first embodiment of the invention. As shown in  FIG. 2   b , the system may include a video encoding end  10   b , a video decoding end  20   b , and a network  30   b  which is respectively connected with video encoding end  10   b  and video decoding end  20   b . Video encoding end  10   b  includes at least a video capture module  11   b , a video encoding module  12   b , a data transmitting module  13   b  and a reference frame judging module  14   b . Video decoding end  20   b  may include a video decoding module  22   b  and a feedback module  24   b . Video capture module  11   b , video encoding module  12   b , data transmitting module  13   b , reference frame judging module  14   b , video decoding module  22   b  and feedback module  24   b  are respectively similar to video capture module  11   a , video encoding module  12   a , data transmitting module  13   a , reference frame judging module  14   a , video decoding module  22   a  and feedback module  24   a  in  FIG. 2   a . No further descriptions will be provided here. 
     Preferably, reference frame judging module  14   b  judges whether video frame information fed back by feedback module  24   b  includes frame-loss information and video frame number information. If yes, operations for determining the reference frame will be executed. 
     When reference frame judging module  14   b  judging the video frame information fed back by feedback module  24   b  doesn&#39;t include frame-loss information and video frame number information, video encoding module  12   b  encodes current video image with a method, in which an I frame is encoded every 20 frames, and a P frame is encoded every 5 frames with the latest I frame as the reference frame. 
     When judging the video frame information fed back by feedback module  24   b  includes the frame-loss information and video frame number information, reference frame judging module  14   b  continuously judges whether there is a video frame corresponding to the video frame number information currently, if yes, takes the video frame corresponding to the video frame number information as the reference frame. 
     When reference frame judging module  14   b  judges there is no video frame corresponding to the video frame number information currently, video encoding module  12   b  encodes current video image in the manner of I frame. 
     Preferably, decoding result includes decoding success and decoding failure. 
     When decoding result of video decoding module  22   b  is decoding failure, feedback module  24   b  feeds back the video frame information to reference frame judging module  14   b  through the network. 
     Preferably, the video frame formed after encoding by video encoding module  12   b  is sent by data transmitting module  13   b  in the manner of video frame data to video decoding end  20   b  through network  30   b . As shown in  FIG. 2   b , video decoding end  20   b  needs to include a data receiving module  21   b  connecting with video decoding module  22   b , which is configured to receive video frame data transmitted by data transmitting module  13   b , to package received video frame data again to form a video frame, and to send the video frame to video decoding module  22   b.    
     In the embodiment, as shown in  FIG. 2   b , video decoding end  20   b  further includes a video playing module  23   b  connecting with video decoding module  22   b , which is configured to play video image decoded successfully. 
     According to video communication technical principle, current video image is an original video image (may also be referred to as original frame), which is captured by video capture module  11   b  and sent to video encoding module  12   b . The video frame is formed after encoding received original frames according to predetermined encoding algorithm by video encoding module  12   b , the encoding mode thereof may be I frame or Inter frame (P frame for short). 
     The I frame refers to an encoding mode, which adopts picture compression technologies and only compresses space redundant information within the video frame. The P frame refers to another encoding mode, which not only compresses space redundant information within the video frame, but also compresses data utilizing time redundant between the video frame and a designated reference frame, that is, the P frame performs time-domain prediction and encoding, and compression efficiency of P frame is much higher than that of the I frame. 
     In the foregoing, the reference frame determined by reference frame judging module  14   b  may be utilized as a reference in subsequent video frame encoding performed by video encoding module  12   b , so as to execute inter-frame encoding. Meanwhile, the reference frame may be a reconstructed frame obtained at video encoding end  10   b  according to the video frame information fed back. As is well known by persons having ordinary skill in the art, the reconstructed frame refers to a video frame formed after performing video encoding on an original video image, e.g., an original frame, captured by video capture module  11   b , in which the video frame is a video frame with loss compared with the original frame. 
     Encoding mode of above reference frame may be I frame, or P frame. The reference frame may be obtained from buffer of video encoding end  10   b  according to the video frame information fed back by feedback module  24   b , in duration between reference frame judging module  14   b  has completed the encoding according to a previous frame and starts to encode current video frame. 
     Encoding technologies of video encoding module  12   b  may be determined according to specific application. Video encoding technologies, such as Audio Video Interleaved (AVI), Moving Picture Experts Group (MPEG), DivX, RealVideo, Windows Media Video, Audio Video Coding Standard (AVS) or/and H.264 may be adopted. Decoding technologies of video decoding module  22   b  correspond to encoding technologies of video encoding module  12   b . No further descriptions are provided here. 
     Video frame information fed back by feedback module  24   b  includes at least one of the follows. Information indicating whether decoding is successful, frame-loss information, video frame number information buffered, reference frame number, frame number information about the last frame buffered in video decoding end  20   b.    
     Data transmitting module  13   b  and data receiving module  12   b  may be network transmission functional interfaces or functional modules of different user terminals. The user terminal may be computer, handheld electronic device, communication device, video monitoring device, etc. Furthermore, the user terminal may be a client run in above devices, such as an Instant Messaging (IM) end, a video communication client. The network transmission functional interface or functional module of the user terminal may be determined according to character of network  30   b . Network  30   b  may also adopt a wired-based network, such as Internet wired network, digital television network. Network  30   b  may also adopt a wireless-based network, such as General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA), Time Division Switching-CDMA (TDS-CDMA), Wireless Fidelity (WiFi), or a wireless network based on IEEE 802.11x series. 
     In the foregoing, detailed descriptions about the system provided by an embodiment of the invention were provided. Preferably, embodiments of the present invention also provide a video encoding communication device on the basis of feedback reference frame correspondingly. With reference to  FIG. 2   c ,  FIG. 2   c  is a diagram illustrating structure of a video encoding communication device on the basis of feedback reference frame provided by an embodiment of the invention. As shown in  FIG. 2   c , the device at least includes a video capture module  11   c  configured to capture current video image, a video encoding module  12   c  configured to encode current video image, and a data transmitting module  13   c  configured to transmit a video frame formed after encoding by video encoding module  12   c  to video decoding end through the network. Preferably, the device further includes the follows. 
     A reference frame judging module  14   c , which is located between video capture module  11   c  and video encoding module  12   c , is configured to obtain video frame information fed back by video decoding end, determine a reference frame used to encode current video image according to the video frame information, and provide the determined reference frame, which is used to perform encoding operations on current video image, to video encoding module  12   c.    
     Preferably, in the embodiment of the invention, there may be multiple implementation modes for reference frame judging module  14   c . As shown in  FIG. 2   c , reference frame judging module  14   c  includes the follows. 
     A first judging unit  11   d , configured to judge whether the video frame information fed back by video decoding end includes frame-loss information and video frame number information. 
     A first determining unit  12   d , when judging result of first judging unit  11   d  is yes, configured to determine a reference frame which is used to encode current video image. 
     When judging result of first judging unit  11   d  is no, video encoding module  12   c  encodes current video image according to a predetermined encoding method. The predetermined encoding method refers to encoding an I frame every 20 frames, and encoding a P frame every 5 frames with the latest I frame as a reference frame. 
     Preferably, as shown in  FIG. 2   d , reference frame judging module  14   c  further includes the follows. 
     A second judging unit  13   d , which is located between first judging unit  11   d  and first determining unit  12   d , when judging result of first judging unit is yes, configured to judge whether there is a video frame corresponding to the video frame number. 
     When judging result of second judging unit  13   d  is yes, first determining unit  12   d  is configured to take the video frame corresponding to the video frame number as a reference frame, 
     Thus, when judging result of second judging unit  13   d  is no, video encoding module  12   c  may encode current video image to form a video frame in the manner of I frame. 
     Until now, descriptions about structure of a video encoding communication device on the basis of feedback reference frame are provided. 
     Preferably, embodiments of the invention also provide a video decoding communication device on the basis of feedback reference frame correspondingly. As shown in  FIG. 2   e , the device at least includes a video decoding module  22   e  configured to decode received video frames. The key is that the device further includes the follows. 
     Feedback module  24   e , which is connected with video decoding module  22   e , is configured to feed back video frame information to video encoding end through the network according to decoding result of video decoding module. 
     The decoding result includes decoding success and decoding failure. 
     When decoding result is decoding failure, feedback module  24   e  is configured to feed back video frame information to video encoding end through the network. When the video frame with failed decoding is a backbone frame, the video frame information carries frame number information about the last frame buffered currently. 
     When implementing specifically, the device further includes the follows. 
     A data receiving module  21   e , which is connected with video decoding module  22   e , is configured to receive video frame data transmitted by video encoding end, package the video frame data to form a video frame again, and provide the video frame to video decoding module  22   e.    
     Video playing module  23   e , configured to play video image decoded successfully, when decoding result of video decoding module  22   e  is decoding success. 
     Until now, descriptions about structure of a video decoding communication device on the basis of feedback reference frame are provided. 
     To make embodiments of the invention more clear, descriptions about flow provided by embodiments of the invention are given. 
     With reference to  FIG. 3 ,  FIG. 3  is a diagram illustrating a basic flow on the basis of  FIG. 2   a  or  FIG. 2   b  in accordance with embodiments of the invention. As shown in  FIG. 3 , the flow may include the following steps. 
     Step S 110 , video encoding end receives video frame information fed back by video decoding end, determines a reference frame used to encode current video image according to the video frame information, encodes current video image according to the determined reference frame, and sends out a video frame formed after encoding. 
     Step S 120 , video decoding end decodes received video frames, and feeds back video frame information to the video encoding end through a network according to decoding result. 
     It can be seen that, step S 110  actually demonstrates operations about video encoding communication on the basis of feedback reference frame provided by an embodiment of the invention, while step S 120  demonstrates operations about video decoding communication on the basis of feedback reference frame provided by an embodiment of the invention. To make the embodiment clearer, descriptions about steps S 110  and S 120  are respectively provided in the following. 
     With reference to  FIG. 4 ,  FIG. 4  is a diagram illustrating flow about video encoding communication on the basis of feedback reference frame in accordance with an embodiment of the invention, which is the detailed description in step S 110 . Meanwhile, the flow may be on the basis of structure illustrated in  FIG. 2   c . As shown in  FIG. 4 , the flow may include the follows. 
     Step S 210 , video encoding end captures original frames of video image. 
     Step S 220 , video frame information fed back is obtained and judged. 
     Step S 230 , a reference frame is determined according to the video frame information fed back; 
     Step S 240 , a video frame is formed after encoding current original frame according to the reference frame; 
     Step S 250 , the video frame formed after encoding is buffered; 
     Step S 260 , encoded video frame is sent to video decoding end; 
     Step S 270 , whether it is necessary to finish video communication is determined, if the video communication is continued, block  210  will be executed; otherwise, the video communication will be finished. 
     The reference frame in step S 230  may be utilized as a reference to execute inter-frame encoding, when video encoding module  12   c  performing subsequent encoding for video frames. Meanwhile, the reference frame in step S 230  may be a reconstructed frame obtained at the video encoding end according to the video frame information fed back. Specifically, a reconstructed frame refers to a video frame formed after performing video encoding on an original video image, e.g., an original frame, captured by video capture module  11   c , in which the video frame carries loss compared with the original frame. 
     Encoding mode of the reference frame may be I frame, or P frame. The reference frame may be obtained from buffer of the video encoding end according to the video frame information fed back, in duration between reference frame judging module  14   c  has completed the encoding according to a previous video frame and starts to encode current video frame. 
     Specifically, the video frame information includes at least one of the following. Information indicating whether decoding is successful, frame-loss information, video frame number information buffered, reference frame number, frame number information about the last frame buffered in video decoding end. 
     The step of obtaining and judging video frame information fed back in step S 220  includes the follows. 
     Step S 221 , whether the video frame information fed back includes frame-loss information and video frame number information is determined. If yes, step S 230  will be executed. Otherwise, step S 222  will be executed. 
     Step S 222 , the video frame is encoded according to a predetermined encoding method. The predetermined encoding method refers to encoding an I frame every 20 frames, and encoding a P frame every 5 frames with the latest I frame as a reference frame. According to requirements of practical application, the predetermined encoding method may refer to an encoding rule, which encodes an I frame every A frames, and encodes a P frame every B frames with the latest I frame as a reference frame. A and B may be arbitrary numbers. 
     Step for determining the reference frame according to the video frame information fed back in step S 230  may include the follows. 
     Step S 231 , whether there is a video frame corresponding to buffered video frame number in a buffer of video encoding end, if yes, step S 232  will be executed; otherwise, step S 233  will be executed. 
     Step S 232 , the video frame corresponding to the buffered video frame number is taken as a reference frame; 
     Step S 233 , a video frame is formed by encoding current original frame in the manner of I frame, and step S 260  may be directly executed. 
     Step for buffering a video frame formed after encoding in step S 250  includes the follows. 
     Step S 251 , number of a video frame formed after encoding is judged. 
     Step S 252 , a video frame corresponding to the video frame number is buffered according to a rule for buffering video frames. 
     The rule for buffering video frames refers to that, if number of a video frame formed after encoding is multiple of a certain number, the video frame will be buffered; otherwise, the video frame will not be buffered. The certain number above in the rule may be numbers, such as 2, 3, 5 and 8. The above buffered video frame is stored in a buffer. The buffer may accommodate a predetermined number of this video frame, e.g., N video frames. The predetermined number N may be defined according to actual requirements, e.g., 5 reconstructed frames encoded, but not limited to this size. Meanwhile, buffered space may be adjusted, e.g., a video frame buffered earliest may be removed when the buffer is full. Specifically, according to principle of accommodating N video frames by the buffer, a video frame buffered earliest may be removed from the video frames buffered currently, and then, N video frames may be buffered, in which N is a predetermined number. 
     Until now, the flow about a video decoding communication method on the basis of feedback reference frame provided by an embodiment of the invention may be implemented. 
     With reference to  FIG. 5 ,  FIG. 5  is a diagram illustrating a flow about video decoding communication on the basis of feedback reference frame in accordance with a third embodiment which is provided based on the first embodiment of the invention.  FIG. 5  illustrates the detailed descriptions in step S 120 . The flow in  FIG. 5  may be on the basis of structure shown in  FIG. 2   e . As shown in  FIG. 5 , the flow may include the following. 
     Step S 310 , video decoding end receives video frame data transmitted by video encoding end, and packages the video frame data to form a video frame again. If the video frame data has been packaged successfully, step S 320  will be executed; otherwise, decoding failed information will be returned. 
     Step S 320 , the video frame with newly and successful package may be decoded. 
     Step S 330 , whether decoding is successful may be judged, if the decoding is successful, step S 360  will be executed; otherwise, step S 340  will be executed. 
     Step S 340 , whether it is necessary to feed back video frame information to video encoding end may be judged, if yes, step S 350  will be executed; otherwise, step S 310  will be executed. 
     Step S 350 , the video frame information is fed back to the video encoding end according to a predetermined feedback rule. 
     Step S 360 , the video frame with successful decoding may be played; during the process of playing the video frame with successful decoding, if it is necessary to finish the video communication, the flow will be finished and exited. Otherwise, step S 310  will be returned. 
     The step for feeding back the video frame information to the video encoding end according to a predetermined feedback rule in step S 350  may include the follows. 
     Step S 351 , whether decoded video frame has already been buffered in the video encoding end may be judged, if yes, step S 352  will be executed; otherwise, step S 353  will be executed. 
     When sending the video frame by the video encoding end, if the video frame has also been buffered currently, an identifier indicating the video frame has been buffered currently will be made for this video frame to be sent out. Thus, when step S 351  being executed, whether the decoded video frame has already been buffered in the video encoding end may be directly judged according to whether the decoded video frame has the identifier. Of course, other operation modes may also be adopted in the embodiment of the invention to facilitate the video decoding end to judge whether the decoded video frame has already been buffered in the video encoding end, which is not specifically limited in the embodiment of the invention. 
     Step S 352 , the decoded video frame is stored in a buffer of video decoding end  20 , and then, step S 353  will be executed. 
     Step S 353 , whether it is necessary to feed back video frame information through a network may be judged according to a predetermined rule, if yes, the video frame information will be fed back, otherwise, no video frame information will be fed back. 
     Specifically, the predetermined rule refers to all the decoding successful information will not be fed back, that is, only when the decoding is failed, video frame information will be fed back in the embodiment, Failed decoding is specifically as follows. For example, video frames with continuous frame numbers are not obtained in a predetermined duration, which is not limited here. 
     The video frame information fed back includes one of the follows. Successful information, frame-loss information, video frame number information buffered, reference frame number, frame number information about the last frame in the buffer of the video decoding end. When the frame number information about the last frame is included, it means that the video frame with unsuccessful decoding is a backbone frame. Here, the backbone frame refers to a video frame, when decoding of the video frame is failed, all of the subsequent frames except for the I frame cannot be decoded correctly. That is, the backbone frame refers to a video frame, which may be decoded separately independent of several proximate video frames in front of it. The several proximate video frames may be one frame proximate with the backbone frame, or may be multiple frames proximate with the backbone frame. 
     The technical scheme provided by embodiments of the invention may be applied in video communication service technologies with feedback channels, e.g., network video playing, video chatting, video conference, video monitoring and Video On Demand (VOD). 
     The foregoing is only preferred embodiments of the invention, which is not used to limit the scope of the invention. Any equivalent structure substitution or flow substitution made utilizing contents of the specification and attached figures in the invention, or applied directly or indirectly in other related technical fields, should be covered by the protection scope of the invention similarly.