Very low bit-rate digital video coding

In this paper, an image sequence coding scheme for very low bit-rate video coding is presented. The new technique utilises windowed overlapped block matching motion compensation for the temporal coding scheme, and vector quantization to reduce the spatial redundancy within the predicted image. When the codec is configured to operate at 11.4 kbit/s, average PSNR values of 33.68dB and 26.71dB are achieved for the Miss America and Carphone sequences respectively. We propose a new methodology for adaptive vector quantization (AVQ), where the codebook is updated with new vectors. The new vectors replace less significant ones in the codebook based on a novel scoring criterion that utilises a forgetting factor and codebook half-life. The proposed method gives rise to an additional performance enhancement of around 1dB over conventional techniques of AVQ. Furthermore, the methods do not suffer from blocking effects due to the inherent properties of both the temporal and spatial coding.