Encoders in different embodiments use different methods for selecting and assigning the additional chroma QP offset values that are specific to a quantization group. Some embodiments perform a pre-analysis step in which the encoder performs a region level analysis. Some embodiments identify different regions in an image that are of different video content type. In some of these embodiments, different regions with different types of video content are assigned different chroma QP offset values or into different quantization groups. Some embodiments distinguish graphics content from real video content. Some embodiments distinguish 4:4:4 video content that are originally coded in 4:4:4 format from 4:4:4 video content that are up-sampled from 4:2:0 format. Some embodiments discern video content that may have originally been of different bit-depths. These characteristics of video content, in addition to their relationships across color components as well as rate control information, are used by some embodiments to determine the quantization levels or quantization relationships among all color components.

The preceding Summary is intended to serve as a brief introduction to some embodiments of the invention. It is not meant to be an introduction or overview of all inventive subject matter disclosed in this document. The Detailed Description that follows and the Drawings that are referred to in the Detailed Description will further describe the embodiments described in the Summary as well as other embodiments. Accordingly, to understand all the embodiments described by this document, a full review of the Summary, Detailed Description, and the Drawings is needed.