Rate Control for Spatial/CGS Scalable Extension of H.264/AVC
This paper presents a rate control scheme for H.264/AVC spatial/ coarse-gain-SNR (CGS) scalable extension. A switched model is proposed to predict mean absolute difference (MAD) either from the previous frame of the current layer or from the current frame of the previous layer. This way, abrupt MAD fluctuations could be predicted properly in the enhancement layer. Moreover, a sum bits R-Q model is formulated to describe the relationship between the total amount of bits for texture and non-texture information and quantization parameter (QP) so as to reduce the negative effect caused by inaccurate non-texture bits estimation of the previous rate control schemes. With the relation between PSNR and QP value of H.264/AVC, our proposed sum bits R-Q model could further optimize the QP calculation at the MB level. With our algorithm, the rate control for all the coarse-grain-scalability (CGS) and spatial enhancement layer could be realized, and the encoder could achieve fixed bitrate encoding for each scalable layer. Our method encodes the sequence only once and the buffer is well controlled to prevent it from overflowing and underflowing.