Adaptive bit allocation scheme for extremely low-delay intraframe rate control in high efficiency video coding

Most existing intraframe rate control algorithms for the high efficiency video coding (HEVC) standard do not consider the extremely low end-to-end delay required by various applications. An intraframe extremely low-delay rate control scheme for HEVC is presented. First, compared with existing intraframe complexity estimation methods in HEVC, the proposed scheme provides a more accurate complexity estimation method by considering spatial–temporal complexity correlations. Second, based on the proposed complexity estimation method, a linear relationship is modeled between the encoding bit rate and the complexity estimated at the largest coding units (LCU) level. Finally, in order to meet the extremely low-delay constraint, an adaptive bit allocation scheme is proposed, in which the rate control starts as soon as the first LCU row of each frame becomes available. Compared with existing intraframe rate control schemes in HEVC, in which the buffer size is far greater than the number of bits needed for encoding one frame, the proposed rate control scheme has a buffer size that is approximately one-third the average number of bits for encoding one frame in order to achieve extremely low delay. Experimental results show that the proposed scheme can keep the buffer in an extreme low status along with reliable coding performance.