FIGS. 5, 6, and 12 have introduced several different methods that a quantization group can use to specify a set of chroma QP offset values. In some embodiments, quantization groups in different pictures or slices may use different methods for specifying chroma QP offset values. An encoder in some of these embodiments selects the best method that it thinks is needed for the current picture or slice in order to achieve higher flexibility or reduce coding overhead.
For some embodiments, FIG. 14 illustrates the pseudo code for a picture header 1400 that includes a selection for a method of specifying additional chroma QP offset values. The picture header 1400 is similar to the picture header 900 in that it includes flags “additional_chroma_qp_offset” (at line 1411) and “chroma_qp_offset_max_depth” (at line 1413). The picture header 1400 also includes the entries of the chroma QP offset table 890 (at lines 1415-1417). However, unlike the picture header 900, the picture header 1400 also specifies a method by setting “chroma_qp_offset_method” (at line 1414).
