Adaptive Lagrange Multiplier Selection Using Classification-Maximization and Its Application to Chroma QP Offset Decision

In this paper, we propose bit allocation between luma samples and chroma samples using chroma quantization parameter (QP) offsets for Cb and Cr. For this work, we propose an efficient adaptive Lagrange multiplier selection method using classification-maximization, and then apply the proposed adaptive Lagrange multiplier selection to decide chroma QP offsets for Cb and Cr. To our knowledge, this is the first proposal to adaptively decide chroma QP offsets. Because the default mapping function between a chroma QP and a luma QP in H.264 is unbalanced at especially low QPs, the proposed chroma QP offset decision achieves improvement up to 0.8 dB from the experimental results.