A spatio-temporal competing scheme for the rate-distortion optimized selection and coding of motion vectors

The recent H.264/MPEG4-AVC video coding standard has achieved a significant bitrate reduction compared to its predecessors. High performance texture coding tools and 1 over 4-pel motion accuracy have however contributed to an increased proportion of bits dedicated to the motion information. The future ITU-T challenge, to provide a codec with 50% bitrate reduction compared to the current H.264, may result in even more accurate motion models. It is consequently of highest interest to reduce the motion information cost. This paper proposes a competitive framework, with spatial and temporal predictors optimally selected by a rate-distortion criterion taking into account the cost of the motion vector and the predictor information. These new methods take benefit of temporal redundancies in the motion field, where the standard spatial median usually fails. Compared to an H.264/MPEG4-AVC standard codec, a systematic bitrate saving reaching up to 20% for complex sequences is reported.