实时H.264视频流的低密度生成矩阵不等差错保护

LDGM-UEP for real-time H. 264 video communications

在有损网络中进行视频传输时,通常采用FEC来保护视频码流。文中提出了一种基于LDGM-UEP的实时H.264视频传输抗误码方法。发送端编码时,依据视频分组的重要性采用LDGM码对多个视频帧分组进行不等差保护,由于校验分组直接附加在数据分组之后,无编码时延。接收端对I帧直接译码,P帧只需根据子GOP中某一帧分组就可以解码显示该帧。若该帧出现误码,则不需等待子GOP中的所有分组都接收而直接对该帧进行误码掩盖,无解码时延。在接收端接收到子GOP中后续的分组后,LDGM译码器将尝试恢复出该子GOP的所有分组,防止误码扩散。实验结果表明,该方法明显优于现有的实时H.264视频通信,可提高实时视频传输的主观感受质量。

When video streams are transmitted over the lossy networks, forward error correction （FEC） codes are usually used to protect them. An error resilience approach for real-time H. 264 video transmission based on FEC-UEP （unequal error protection） is proposed. With the proposed approach, multiple video frames are protected by the LDGM-UEP algorithm according to the importance levels of video packets, thus enhancing the performance of low density generator matrix（LDGM） codes. Because the check packets are directly added after the data packets, it has no decoding dalay. The video frames are immediately decoded for I frame. And for P frame, decoding can be completed only depending on some frames of sub GOP, thus it is suitable for real time video communications. Experimental results show the proposed approach is better than existing approaches, improving the quality of experience （QoS） significantly.