Color Index Coding with Cross Block Prediction
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Solution Overview
Problem
Existing color index coding techniques for video data, such as those in High Efficiency Video Coding (HEVC) standards, face limitations in coding efficiency due to the complexity of predicting and transmitting color palettes across block boundaries, particularly in screen content coding where the number of colors is limited but the combinations are vast.
Innovation Solution
The method involves using index prediction based on reconstructed neighboring pixels to improve color index coding efficiency by transforming neighboring pixel values into color indices through a quantization table, allowing for more effective mapping and prediction of current pixel indices, thereby reducing the need for escape indices and enhancing parsing throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If color index coding with traditional palette prediction is used, then color information can be transmitted, but the complexity of predicting and transmitting color palettes across block boundaries increases and coding efficiency is limited
Solution Approach 1:
The patent extracts the color palette information from the traditional block-based prediction approach and replaces it with a simplified index prediction mechanism. Instead of transmitting and predicting full color palettes across block boundaries, the invention uses a virtual palette and index prediction based on neighboring reconstructed pixels, thereby removing the complexity of palette transmission while preserving color information efficiency.
Solution Approach 2:
The invention changes the parameter representation from full color palette values to simplified color indices. By using a virtual palette constructed at the decoder side and predicting only indices rather than full color values, the system reduces the amount of data to be transmitted and processed, improving coding efficiency while reducing complexity.
2Measurement precision
If more color indices are transmitted to maintain accuracy, then color representation improves, but bitrate increases
Solution Approach 1:
The patent performs preliminary construction of a virtual palette at the decoder side before actual decoding. By pre-defining the virtual palette and using index prediction based on neighboring reconstructed pixels, the system ensures accurate color representation is achieved through intelligent prediction rather than transmitting all possible color indices, thereby reducing bitrate while maintaining precision.
Solution Approach 2:
The invention uses feedback from neighboring reconstructed pixels to predict current pixel indices. By leveraging the spatial correlation and using already-decoded neighboring pixel values as predictors, the system achieves accurate color representation with fewer transmitted indices, effectively reducing bitrate while maintaining measurement precision.
Data Source
AI summary
A method and apparatus for color index coding of a block of video data using index prediction based on reconstructed neighboring pixels are disclosed. In one embodiment, color index encoding or decoding is applied to the current pixel indices by deriving index prediction from neighboring pixel indices of the reconstructed neighboring pixels. The reconstructed neighboring pixel values are first transformed into the neighboring pixel indices according to a quantization table to map between major color indices and major color values of the current block. The quantization table can be based on a major color table for the current block or can also be derived at a decoder side. The decoding process may reconstruct the current pixels by converting decoded current pixel indices to reconstructed current pixel values according to the quantization table or by directly copying the reconstructed neighboring pixel values indicated by decoded current pixel indices.