An adaptive quantization using modified QP in H.264

An adaptive quantization scheme for the H.264 encoder is proposed In this work. We utilize the information obtained from the previously encoded image. The reconstructed error of each macroblock (MB) can be estimated from the previous frame. For the estimation of the error of the current MB, a block with the size of MB in the previous frame is chosen. Since the original and reconstructed images of the previous frame are available in the encoder, we can evaluate the tendency of reconstruction error of the current MB in advance. Then, this error is considered as the expected error of the current MB. Comparing the error of the MB with the average of overall MB, if it is larger than the average, a small step size is given for this MB, and vice versa. Experimental results show that the rate control algorithm outperforms the conventional scheme. Furthermore, the proposed algorithm is so simple that is only introduces a little computational complexity. Therefore, it can be used in real time video coding.