Interpolation free sub-pixel motion estimation for H.264

Sub-pixel motion compensation plays an important role in compression efficiency within modem video codecs such as MPEG2, MPEG4 and H.264. Sub-pixel motion compensation is implemented within these standards using interpolated pixel values at (1)/(2) or (1)/(4) pixel accuracy. Such interpolation gives a good reduction in residual energy for each predicted macroblock and therefore improves compression. However, such interpolation is very computationally complex for the encoder. This is especially true for H.264 where the cost of an exhaustive set of macroblock segmentations need to be estimated in order to obtain an optimal mode for prediction. This paper presents a novel interpolation-free scheme for sub-pixel motion compensation using the result of the full pixel SAD distribution of each motion compensated block applied to an H.264 encoder. This system produces reduced complexity motion compensation with a controllable trade-off between compression performance and encoder speed. These methods facilitate the generation of a real time software H.264 encode.