Image Stream Decoding with Adaptive Intra-Prediction Syntax
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Solution Overview
Problem
Existing video compression techniques, such as those in the HEVC standard, are not optimal for intra prediction, leading to suboptimal compression ratios and inefficiencies in pixel prediction and reconstruction processes, particularly in the case of lossless coding and inverse transform operations.
Innovation Solution
A method that employs two distinct coding modes for image blocks, using a first group of syntax elements for conventional intra prediction and a second, subgroup of syntax elements for pixel-based intra prediction, allowing for adaptive compression based on coefficient statistics, and optimizing the coding of prediction residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional intra prediction with full syntax elements is used, then prediction accuracy is maintained, but implementation cost and data stream complexity increase
Solution Approach 1:
The syntax elements are segmented into two groups: a first group used for conventional intra prediction and a second group (subgroup) used for the improved pixel-based prediction. This segmentation allows the decoder to use only the necessary syntax elements for the selected prediction mode, reducing implementation complexity while maintaining prediction accuracy when needed.
Solution Approach 2:
The prediction system dynamically selects between two coding modes (conventional intra prediction and pixel-based intra prediction) based on the characteristics of the current block. This dynamic selection allows the system to adapt to different image content requirements, using the simpler conventional mode when sufficient and the more accurate pixel-based mode when needed, thereby optimizing the trade-off between implementation cost and prediction accuracy.
2Productivity
If pixel-based intra prediction with subgroup syntax elements is used, then compression efficiency improves, but compatibility with existing decoders decreases
Solution Approach 1:
The syntax element groups are designed with universality in mind: the second group (subgroup) is a subset of the first group, meaning that a decoder implementing the full first group can handle both conventional intra prediction and the improved pixel-based prediction. This multi-functionality ensures backward compatibility while enabling enhanced compression efficiency when the pixel-based mode is used.
Solution Approach 2:
By segmenting syntax elements into hierarchical groups where the second group is a subgroup of the first, the patent enables decoders to selectively implement only the syntax elements they need. Existing decoders can continue to use the first group for conventional prediction, while new decoders can implement both groups to support the more efficient pixel-based prediction mode, thus maintaining compatibility while improving compression.
3Manufacturing precision
If lossless coding with prediction residue addition is used, then reconstruction accuracy is achieved, but compression ratio remains low
Solution Approach 1:
The patent applies prediction operations before the final reconstruction step. By predicting pixels from already reconstructed pixels within the same block (pixel-based intra prediction), the method reduces the magnitude of prediction residues that need to be encoded. This preliminary prediction action enables better compression ratios while maintaining lossless reconstruction accuracy, as the residues become smaller and more compressible.
Data Source
AI summary
A method for decoding a coded data stream representative of at least one image that is split into blocks. For at least one block of the image, referred to as the current block, an item of information indicating a coding mode of the current block is decoded from the data stream. When the coding mode of the current block corresponds to a first coding mode, decoding a prediction residue associated with the current block using a first group of syntax elements. When the coding mode of the current block corresponds to a second coding mode, decoding the prediction residue associated with the current block using a second group of syntax elements, which is a subgroup of syntax elements of the first group of syntax elements.