Nested interleaving transcoder for MPEG-4 Simple Profile bitstream

We propose a nested interleaving scheme in order to provide three levels of synchronization in a compressed video bitstream for low data rate wireless applications. The first level of interleaving specifies the starting position of each macroblock (MB) in a video frame. The second level of interleaving provides the start position of each MB header codeword and the start position of each DCT block. The start position of each VLC in a DCT block is located in a known position by the third level of interleaving. Our scheme is assumed to operate in the form of a transcoder, placed before and after the channel, of a MPEG-4 Simple Profile bitstream. Since the three level interleaving provides synchronization on a VLC scale, syntax-based bit error detections can be done in a VLC unit. The detected errors can be repaired syntactically so that the transcoder generates a MPEG-4 compliant bitstream which can then be decoded with a standard MPEG-4 decoder such as MoMuSys (FDIS V1.0).