Abstract:

Intraframe encoding in H.264/AVC video standard usually adopts Rate Distortion Optimization (RDO) technique. By computing all possible coding modes, the one which has the lowest cost of rate distortion is selected as the best mode. The RDO technique improves the reliability, accuracy and error resilience of encoding while increasing the complexity and search time of the encoding. The residual value between the current and reconstructed 4×4 block is calculated in the circumstances of analyzing the standard intraprediction. If the value is smaller than a certain threshold the macro block coding can be ended in advance. Conversely, a fast 4×4 intraprediction mode selection algorithm was proposed by utilizing the correlation between the texture direction of block and the choice of predict modes. Based on the improved Canny operator and square gradient method, this algorithm extracts the texture of the current block and analyzes the corresponding relations between texture direction and the predict modes in detail. Experiments were carried out on the reference model JM13.2 of H.264/AVC. The results show that, compared with the standard algorithm, the encoding time is substantially declined in the case of keeping the bit rate and the PSNR are nearly unchanged.

Key words: H.264/AVC;intraprediction;Canny operator;square gradient;texture direction