Adaptive prediction and vector quantization based very low bit rate video codec

Abstract

A very low bit rate video codec (coder/decoder) based on motion compensation, adaptive prediction, vector quantization (VQ) and entropy coding, and a new prediction scheme based on Gibbs random field (GRF) model are presented. The codec is specifically designed for the video-phone application for which the main constraint is to transmit the coded bit stream via the existing telephone lines. Proposed codec can operate in the transmission bit rate interval ranging from 8 to 32 Kbits/s which is defined as the very low bit rates for video coding. Four different coding strategies are adapted to the system, and depending on the characteristics of the image data in the block one of these coding methods is chosen by the coder. Linear prediction is implemented in the codec, and the performances of the two prediction schemes are compared at several transmission bit rates. The need for any prediction is also questioned, by implementing the same codec structure without prediction and comparing the performances of the codecs with prediction and without prediction. It is proved that the presented codec can be used in transmitting the video signal via the existing telephone network for the video-phone applications. Also, it is observed that the codec with GRF model based non-linear prediction has a better performance compared to the codec with linear prediction.