Adaptive Color Transform Block Partitioning for Video Compression

The patent implements dynamic adjustment of color transform parameters by introducing flags (e.g., sps_act_enabled_flag, cu_act_enabled_flag) that allow the encoder to selectively enable ACT mode for specific video blocks based on their characteristics. The transform parameters are dynamically changed between different color spaces (YCbCr, YCoCg, YCgCo) on a block-by-block basis, optimizing compression efficiency while managing complexity through conditional application rather than universal implementation.

The patent applies different color transform characteristics to different regions of the video content by enabling ACT selectively at the coding unit level. Each video block can be independently evaluated and processed with appropriate color transform parameters based on local content characteristics, allowing high compression efficiency in suitable regions while avoiding unnecessary processing in regions where ACT is not beneficial.

The patent applies ACT mode selectively rather than universally by introducing enablement flags that control application on a per-block basis. The encoder evaluates each video block's characteristics and applies ACT only where it provides compression benefits, avoiding excessive action on blocks where it would not improve performance, thus optimizing the balance between compression performance and bandwidth usage.

The patent changes the parameter of ACT application from a fixed global setting to a dynamic conditional parameter controlled by enablement flags and block size thresholds. This allows the system to adapt the quantity and distribution of ACT application based on content characteristics, reducing unnecessary bandwidth consumption while maintaining compression performance where beneficial.

The patent segments video blocks into sub-blocks and enables ACT independently at the sub-block level through partitioning. This allows different portions of a larger block to have different ACT enablement states, improving compression efficiency by applying the transform only where needed within the block while maintaining manageable processing complexity through systematic segmentation.

The patent introduces an additional dimension of control by enabling ACT at the sub-block level rather than only at the full block level. This granular control allows independent optimization of each sub-block, improving overall compression efficiency while distributing processing complexity across multiple smaller, independently manageable units.