Lossless FMO and Slice Structure Modification for Compressed H.264 Video

We introduce a scheme to losslessly modify pre-compressed H.264 video to enable at streaming time (1) modification of slice sizes to fit transport packet size, and (2) introduction of an error resilience feature, namely flexible macroblock ordering. By lossless we mean the reconstructed video from the modified bitstream is identical to that from the original compressed bitstream. We outline how this transcoder operates, and discuss some of its restrictions. The bit rate overhead for operating on the pre-compressed, rather than directly encoding the original video with the desired characteristics, is analyzed. Simulation results show 1 to 2 dB improvement when our scheme is applied to QuickTime generated H.264 videos transported over a lossy packet network.