H.264 Transcoding of B to P slices by Reusing Motion Vector and Residual Data

We propose a transcoding scheme for converting B to P slices in the H.264 video coding standard without spatial resolution change. When a receiver such as portable player of baseline profile wants to show contents of main profile encoded in the bi-predictive mode, it is desirable to convert B to P slices instead of just discarding the B slices. The proposed scheme makes use of motion vector and its refinement. To utilize previous coding modes and residual data, we develop two mode decision methods of probability-based and neighbor mode-based ones. The experiment results shows that the proposed method speeds up by approximately 54-68% while minimizing quality distortion, as compared to fully re-encoding method.