Hybrid DFT/DPCM interframe image quantization

A non-adaptive scheme for encoding an image sequence is described that yields better results than any previous comparable interframe image coding method. The scheme uses a hybrid of two-dimensional transform coding for the spatial dimension and DPCM for the time dimension similar to some previous works [e.g., 1]. Unlike the previous efforts, which use discrete cosine transforms (DCT´s) of image subblocks and suboptimal quantization, we utilize a full image DFT and an optimal quantization algorithm. The results with the standard sixteen frame sequence of Walter Cronkite are visually superior to previous transform coding efforts, especially at rates lower than 1 bit/pixel/ frame. The signal-to-noise ratios are higher than those of nonadaptive hybrid DCT/DPCM in [1] by 2.6 to 10.5 dB depending on rate.