A frame-layer bit allocation for H.263+

In typical block-based video coding, the rate-control scheme allocates a target number of bits to each frame of a video sequence and selects the block quantization parameters to meet the frame targets. In this work, we present a new technique for assigning such targets. This method has been adopted in the test model TMN10 of H.263+, but it is applicable to any video coder and is particularly useful for those that use B frames. Our approach selects the frame targets using formulas that result from combining an analytical rate-distortion optimization and a heuristic technique that compensates for the distortion dependency among frames. The method does not require pre-analyses, and encodes each frame only once; hence, it is geared toward low-complexity real-time video coding. We compare this new frame-layer bit allocation in TMN10 to that in MPEG-2's TM5 for a variety of bit rates and video sequences.