Error concealment, early re-synchronization, and iterative decoding for MPEG-2

For the digital transmission of TV the video-signal will be highly compressed with the MPEG-2 source coding algorithm. The MPEG-2 source coded stream is very sensitive to channel disturbances due to variable length coding. A single bit error may result in error propagation, therefore, it will cause a high degradation of picture quality. Hence, error concealment techniques or iterative decoding techniques might be required at the receiver. The aim of this article is to study different techniques for handling channel errors at the receiver side. The first way is to apply error concealment techniques after source decoding. For P- and B-pictures, the inherent motion vectors can be used for temporal error concealment (TEC) which yields very good results. However, in I-pictures no motion vectors exist for TEC. Furthermore, the spatial error concealment (SEC) techniques suffer from the non existence of neighbored macroblocks (MBs) because of the re-synchronization at the slice level. Therefore, another technique, which is called early re-synchronization, in combination with an enhanced error detection technique is investigated in this article. With this technique most of the correct received data can be exploited for error concealment and the quality of service mainly in I-pictures will be improved. A second way for handling channel errors is to apply iterative channel decoding. With this, the error correction capability of the channel decoding part can be improved and less residual errors will occur in the bitstream