Robust H.263+ video transmission using partial backward decodable bit stream (PBDBS)

We propose a novel robust H.263+ video transmission scheme using a partial backward decodable bit stream (PBDBS), which reverses the bit stream of some coded macroblocks (MBs) so that these coded MBs can be decoded in a backward direction. Because of using variable-length coding (VLC), the baseline H.263+ coder will lose synchronization until the next resynchronization marker when errors occur in the coded bit stream. It is wasteful to discard all of the remaining coded MBs in a group of blocks (GOB). Our method is to alleviate this effect by reversing the bitstream that belongs to the coded second half row of MBs in a GOB. When a decoder loses resynchronization, it will search the next resynchronization marker and decode the bitstream backward. It can retrieve half row of MBs that are lost otherwise. This method combined with error concealment can greatly improve the transmitted image quality. Up to 2-dB luminance peak signal-to-noise ratio improvement can be found in our method compared with the baseline H.263+ coder. We also compare our PBDBS method with H.263++ Annex V using data partitioning and reversible VLC. Under lower encoder and decoder complexity, the PBDBS method obtains more pleasant results than Annex V, and it can be utilized in noisy channels such as wireless networks.