Subband dictionaries for low-cost matching pursuits of video residues

Matching pursuits" is a signal expansion technique whose efficiency for video coding has already been largely demonstrated in the MPEG-4 framework. In this paper, our attention focuses on complexity issues. First, the most expensive step of the signal expansion process is significantly speeded up by exploiting results achieved in the wavelet and multiresolution theory. A subband dictionary is proposed as an alternative to the Gabor dictionary that has been used up to now. Equivalent levels of quality are achieved with both dictionaries, but the computational cost is significantly reduced when using the subband one. Then, we explain how, with any dictionary, the linearity of the inner product could be exploited to further speed up the process in return for an increased amount of memory.