Mode Refinement Algorithm for H.264 Inter Frame Requantization

The latest video coding standard H.264 has been recently approved and has already been adopted for numerous applications including HD-DVD and satellite broadcast. To allow interconnectivity between different applications using H.264, transcoding will be a key factor. When requantizing a bitstream the incoming coding decisions are usually kept unchanged to reduce the complexity, but it can have a major impact on the coding efficiency. This paper proposes a novel algorithm for mode refinement of inter prediction in the case of requantization of H.264 bitstreams. The proposed approach gives a comparable quality to a full search for a fraction of its complexity by exploiting the statistical properties of the mode distribution and motion vector refinement.