Palette Coding Prediction for Screen Content Images
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Solution Overview
Problem
Existing image coding technologies face inefficiencies in compressing screen content images due to low pixel value correlation and limited color variations, leading to increased transmission of palette information and reduced coding efficiency when adjoining blocks have not received palette coding.
Innovation Solution
An image coding device generates and stores palette information from decoded images of adjoining blocks to predict and encode palette information for coding target blocks, allowing prediction coding even when adjoining blocks have not received palette coding, thereby reducing the need for explicit transmission of palette information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DCT is applied to screen content images with low pixel correlation regions, then compression coding is performed, but mosquito distortions are perceived visually and remarkably under low bitrate conditions
Solution Approach 1:
The patent changes the coding parameters by switching from DCT-based coding to palette-based coding for screen content images. It determines whether to apply palette coding based on characteristics like low pixel correlation and limited color variations, using different coding methods for different image types to avoid mosquito distortions while maintaining compression efficiency
Solution Approach 2:
The patent segments the image coding process into different modes: DCT-based coding for natural images and palette-based coding for screen content images. It divides the coding strategy based on image characteristics such as pixel correlation and color variation, applying the appropriate method to each region or image type
2Manufacturing precision
If palette information is explicitly transmitted for all blocks, then accurate color reproduction is maintained, but transmission bandwidth and coding time increase
Solution Approach 1:
The patent uses feedback from neighboring blocks to generate palette information for the current block. By examining the palette information of adjacent blocks and using prediction coding, the system can accurately reproduce colors without transmitting all palette information explicitly, reducing data volume while maintaining accuracy
Solution Approach 2:
The patent copies or predicts palette information from neighboring blocks rather than transmitting it explicitly for every block. This prediction approach allows the decoder to reconstruct palette information without receiving it directly, reducing transmission requirements while maintaining color accuracy
3Device complexity
If prediction coding is performed only when adjoining blocks have received palette coding, then coding simplicity is maintained, but coding efficiency is reduced for screen content images
Solution Approach 1:
The patent performs preliminary actions by generating palette information for adjoining blocks even when they have not received explicit palette coding. This allows the current block to use prediction coding based on these pre-generated palettes, improving efficiency without significantly increasing complexity
Solution Approach 2:
The patent introduces an intermediary mechanism where palette information can be generated and stored for adjoining blocks as a reference. This intermediary palette information enables prediction coding for the current block even when the adjoining block hasn't been explicitly palette-coded, improving coding efficiency
Data Source
AI summary
A generation circuit generates first palette information from a decoded image of a first block used for predicting second palette information of a second block in a coding target image when the first block has not received palette coding. A storage circuit stores the first palette information. A coding circuit performs prediction coding on the second palette information by using the first palette information so as to generate coded palette information.