Frame layer bit allocation scheme for constant quality video

In order to achieve constant quality across the whole video sequence under the channel bandwidth and buffer constraints, it is necessary to allocate more bits to frames with scene changes or high complexity and fewer bits to low complexity frames. In this work, we propose a new frame layer bit allocation scheme for H.264 video coding using mean absolute difference (MAD) ratio, which is the ratio of MAD of current frame to the average MAD from the starting frame up to the previous frame in a GOP. We provide a theoretical justification of MAD ratio as a measure of frame complexity. Bit budget is allocated to frames according to their MAD ratios, combined with the bits computed based on their buffer status. Simulation results show that the H.264 coder, using our proposed algorithm with virtually little computational complexity added, effectively alleviates visual quality degradation caused by high motion or scene changes. Our proposed algorithm significantly reduces the standard deviation of PSNR, hence producing a nearly constant video quality throughout the whole video sequence, when compared with other existing video schemes.