Single-Pass Entropy Coding for Last Non-Zero Transform Coefficients
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Solution Overview
Problem
Current entropy coding methods, such as CABAC, are inefficient for larger block sizes in video coding due to the need for two scanning passes and lack of systematic implementation, leading to increased complexity and reduced compression efficiency.
Innovation Solution
A systematic entropy coding approach that uses a flag to indicate the last non-zero coefficient in a block, allowing for encoding and decoding in a single scanning pass, reducing binary bins and improving compression efficiency by eliminating unnecessary binary arithmetic coding operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CABAC coding is used for quantized transform coefficients, then coding efficiency is improved, but two scanning passes are required which increases complexity
Solution Approach 1:
The patent combines the significance map coding and non-zero value coding into a single unified scanning pass. Instead of performing separate forward zigzag scanning for significance flags and inverse zigzag scanning for values, the method integrates both operations into one systematic pass through the transform coefficients, thereby reducing the number of passes from two to one while maintaining CABAC's high coding efficiency
Solution Approach 2:
The patent implements continuous coding by processing coefficients in a single systematic scanning order without interruption or reversal. The coding process continuously progresses through the coefficient block from start to finish, eliminating the need to reverse scanning direction between passes, which reduces complexity while maintaining continuous useful action throughout the encoding process
2Productivity
If CABAC coding is used for larger block sizes, then compression efficiency is maintained, but the non-systematic implementation reduces effectiveness
Solution Approach 1:
The patent changes the fundamental parameter of scanning methodology from the traditional two-pass approach (forward zigzag then inverse zigzag) to a single systematic scanning pass. This parameter change makes the coding process more adaptable to larger block sizes by providing a consistent, predictable scanning pattern that scales effectively with block dimensions while maintaining compression efficiency
3Loss of information
If two scanning passes are performed for CABAC coding, then significance map and non-zero values are coded, but binary bins are increased leading to more arithmetic coding operations
Solution Approach 1:
The patent merges the coding of significance flags and non-zero values into a single scanning pass, which eliminates the redundant binary bins generated by the second scanning pass in traditional CABAC. By combining these operations, the total number of binary bins is reduced while ensuring that all significance map and non-zero value information is still properly coded
Solution Approach 2:
The patent extracts and eliminates the unnecessary second scanning pass from the CABAC coding process. By removing this redundant pass, the method extracts only the essential information needed in a single systematic scan, thereby reducing the quantity of binary bins that require arithmetic coding operations while still capturing all necessary coefficient data
Data Source
AI summary
Methods and apparatus are provided for improved entropy encoding and decoding. An apparatus includes a video encoder (200) for encoding at least a block in a picture by transforming a residue of the block to obtain transform coefficients, quantizing the transform coefficients to obtain quantized transform coefficients, and entropy coding the quantized transform coefficients. The quantized transform coefficients are encoded using a flag to indicate that a current one of the quantized transform coefficients being processed is a last non-zero coefficient for the block having a value greater than or equal to a specified value.