Palette Mode Video Decoding for Block Size and Compression Control

The patent segments the video block into multiple regions (first region, second region, third region) with different prediction modes. The first region uses palette mode with copy from above, the second region uses palette mode with index, and the third region uses traditional prediction modes. This segmentation allows the system to apply simple palette-based copying where applicable while maintaining traditional prediction where needed, thereby improving data efficiency without uniformly increasing complexity across the entire block.

The patent employs copying mechanisms in palette mode where pixel values are copied from above (from previously decoded pixels) or from reference pixels. This copying approach significantly reduces the data that needs to be transmitted and processed compared to traditional prediction methods, improving data efficiency while keeping the decoding process relatively simple through straightforward copy operations.

The patent applies different prediction modes to different regions within the same video block based on local characteristics. Regions with horizontal transitions use palette mode with copy from above, regions with vertical transitions use traditional vertical prediction, and regions with both transitions use palette mode with index. This local adaptation ensures that each region is coded with the most appropriate method, maintaining image quality in areas requiring precision while achieving high compression in areas suitable for palette mode.

The patent dynamically selects prediction modes for different regions within a video block based on gradient calculations and transition detection. The mode selection is not static but adapts to the local content characteristics, allowing the system to achieve high overall compression while preserving image quality in regions where it matters most by using more sophisticated prediction only where necessary.

The patent applies palette mode partially rather than universally - only to specific regions within video blocks where it is most beneficial (regions with horizontal transitions or suitable for palette representation). By applying palette mode selectively rather than excessively to all blocks, the system achieves significant compression efficiency improvements while avoiding the prohibitive computational cost of universal palette mode application.

The patent segments video blocks into regions suitable for palette mode and regions better suited for traditional prediction modes. This segmentation allows the system to reap the compression benefits of palette mode where applicable while maintaining simpler processing in regions where traditional modes are more efficient, thereby improving overall compression efficiency without uniformly increasing processing complexity.

The patent uses a periodic or alternating structure in its region-based prediction approach, where different prediction modes are applied in an alternating fashion across different regions (first region, second region, third region). This structured alternation allows the decoder to efficiently process different mode types in sequence, maintaining image quality through appropriate mode selection while optimizing encoding and decoding time through predictable, structured processing rather than complex uniform processing.

The patent extracts and handles complex prediction operations only where necessary - specifically in regions requiring vertical prediction or both horizontal and vertical transitions. By taking out the complex processing requirements from the entire block and concentrating them only in necessary regions, the system maintains image quality where needed while significantly reducing overall encoding and decoding time compared to applying complex modes universally.