Optimal two-pass frame-layer bit allocation for H.264 Video

In this work, the frame-layer bit allocation problem is studied for H.264 video. We first impose a GOP (Group of Pictures) structure on the underlying H.264 video, and then develop a two-pass rate control algorithm based on the Lagrange optimization framework. The proposed algorithm estimates the rates and the distortions of all frames in a GOP by preencoding them using a constant quantization parameter (QP) in the first pass. The target number of bits of each frame is determined by searching the Lagrange multiplier that meets the bit budget constraint for the GOP. The proposed algorithm is useful for nonconversational applications such as video streaming where video sources can be encoded off-line. Experimental results demonstrate that the proposed algorithm achieves substantially higher picture quality than the rate control algorithm in the H.264 reference encoder.