Transform Coefficient Prediction for Image Compression
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Solution Overview
Problem
Block transform-based coding systems face challenges in efficiently predicting and encoding transform coefficients, particularly due to correlations between adjacent blocks, which can lead to visual artifacts and increased complexity when dealing with directional features in images and videos.
Innovation Solution
A predictive transform coefficient coding technique that calculates directionality metrics for DC and DCAC coefficients, using information from neighboring blocks and channels to determine dominant directionality, and applies specific prediction modes based on these metrics to minimize memory footprint and maintain coding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If block transform-based coding is used to compress digital media, then compression efficiency is improved, but visual artifacts and complexity increase due to correlations between adjacent blocks
Solution Approach 1:
The patent applies preliminary action by predicting transform coefficients of current blocks based on already decoded neighboring blocks before actual encoding. The decoder uses previously decoded blocks to generate prediction values, reducing the information that needs to be transmitted and simplifying the encoding process.
Solution Approach 2:
The patent introduces an intermediary prediction mechanism that mediates between adjacent blocks. A prediction module generates intermediate prediction values based on neighboring blocks, which then serve as the basis for encoding current blocks, reducing direct complexity while maintaining compression efficiency.
2Ease of operation
If transform coefficients are encoded without considering directional features, then encoding simplicity is maintained, but visual artifacts increase due to block discontinuities
Solution Approach 1:
The patent applies dynamics by adaptively selecting prediction modes based on the directional characteristics of neighboring blocks. The system dynamically adjusts prediction strategies according to whether horizontal or vertical correlations are stronger, reducing visual artifacts while maintaining encoding simplicity through automated adaptation.
Solution Approach 2:
The patent changes parameters by adjusting prediction modes and weighting factors based on detected directional features. When strong horizontal or vertical correlations are detected, the system modifies prediction parameters accordingly, reducing block discontinuities without significantly complicating the encoding process.
3Productivity
If memory footprint is reduced by minimizing stored information, then processing efficiency improves, but prediction accuracy may deteriorate
Solution Approach 1:
The patent extracts only the essential information needed for prediction from neighboring blocks, storing and transmitting only the necessary prediction residues and mode indicators. This selective extraction maintains prediction accuracy while minimizing memory footprint and improving processing efficiency.
Solution Approach 2:
The patent uses copying by replicating prediction values from neighboring blocks rather than storing complete block data. The decoder copies and adapts prediction values from already decoded blocks, reducing memory requirements while maintaining sufficient prediction accuracy through intelligent selection of source blocks.
Data Source
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AI summary
A block transform-based digital media codec uses a transform coefficient prediction that takes into account a dominant directionality of the digital media data (e.g., an image with strong horizontal or vertical features), and further operates compatibly with a two-stage transform. For DC and DCAC coefficients from an inner stage transform of a macroblock, the codec calculates and compares directionality metrics based on inner stage transform DC coefficients of neighboring macroblocks to determine dominant directionality. For DCAC coefficients from an outer stage transform of blocks within the macroblock, the codec calculates and compares directionality metrics based on the inner stage transform DCAC coefficients of the macroblock to detect dominant directionality. The determination of directional dominance can also take into account information from other channels (e.g., chrominance as well as luminance).