Adaptive Transform Scan Ordering for Efficient Entropy Coding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing video coding methods inefficiently encode zero value coefficients interspersed with non-zero coefficients due to mismatched probability distributions in defined scan orders, leading to suboptimal compression efficiency.
Innovation Solution
Implementing a context adaptive scan order for entropy coding that assigns transform coefficients based on descending probabilities of being non-zero, maintaining correspondence with context coefficients to improve coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a defined scan order is used for entropy coding, then the coding process is simple and fast, but the compression efficiency is suboptimal due to mismatched probability distributions
Solution Approach 1:
The scan order is made dynamic and adaptive rather than fixed. The entropy encoding unit determines scan orders based on context information from previously coded coefficients, allowing the scan pattern to adapt to the actual distribution of non-zero coefficients in the current block, thereby improving compression efficiency while maintaining manageable complexity through contextual adaptation
Solution Approach 2:
The scan order parameters are changed dynamically based on probability distributions of coefficient locations. By calculating and using context-adaptive probability distributions to determine scan orders, the system optimizes the mapping between coefficient locations and scan positions, resolving the contradiction between simple fixed scan orders and efficient adaptive scanning
2Productivity
If coefficients are encoded in a fixed scan order, then the encoding process is straightforward, but zero value coefficients interspersed with non-zero coefficients are inefficiently encoded
Solution Approach 1:
Different scan orders are applied to different regions or contexts within the transform block based on local probability distributions. By determining context-specific scan orders for different coefficient locations rather than using a single global scan order, the system efficiently handles regions with varying densities of non-zero coefficients, reducing redundancy without compromising coding simplicity
Solution Approach 2:
The encoding process uses feedback from previously coded coefficients to determine the scan order for current coefficients. The entropy encoding unit calculates probability distributions based on context information from already-encoded coefficients and uses this feedback to adaptively select scan orders, thereby improving the efficient encoding of mixed zero and non-zero coefficient patterns
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Video coding using a context adaptive scan order for entropy coding may include decoding a current block by identifying a context adaptive scan order for entropy decoding a transform block, which may include identifying non-zero-coefficient probabilities for the transform block such that each location in the transform block corresponds to a respective non-zero-coefficient probability from the non-zero-coefficient probabilities, assigning a respective context adaptive scan order position to each location in the transform block in descending magnitude order of the respective corresponding non-zero-coefficient probabilities such that the context adaptive scan order position for each location exceeds the context adaptive scan order position assigned to entropy coding context locations for the respective location, entropy decoding transform coefficients from the encoded video stream based on the context adaptive scan order, and reconstructing the decoded block based on the transform block.