A novel fine rate control algorithm with adaptive rounding offset

The rate control algorithm is of essential importance to a video encoder. It enables the encoded bitstream to meet the bandwidth and storage requirement while maintaining good video quality. Most existing works adjust the quantization step size to achieve the required bit rate accuracy. This paper introduces a new dimension: the quantization rounding offset into a frame-level fine rate control algorithm. Specifically, we propose a novel fine rate control algorithm based on a linear model between the bit rate and the rounding offset. Unlike the quantization step size that has a limited number of choices, the quantization rounding offset is a continuously adjustable variable which allows the rate control algorithm to reach any precision in principle. Extensive experiment results show that the proposed algorithm greatly improves the bit rate accuracy and provides better visual quality by fine tuning of the rounding offset in addition to the quantization step size.