Coding Last Significant Coefficient Flags in Video Transform Blocks
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Solution Overview
Problem
Current video compression techniques face inefficiencies in encoding and decoding video streams, particularly in representing the location of the last non-zero coefficient in transform blocks, which affects the bitstream size and computational resources.
Innovation Solution
The proposed solution involves decoding a transform block using a scan order, where a processor determines the offset and position of the last non-zero coefficient within a group of consecutive scan positions, allowing for efficient encoding and decoding of end-of-block positions across both dense and sparse transform blocks using various coordinate systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional encoding techniques are used to represent the location of the last non-zero coefficient, then the bitstream size increases and computational resources are consumed, but the coding efficiency is insufficient
Solution Approach 1:
The transform block is divided into groups of consecutive scan positions, and the last non-zero coefficient position is encoded by specifying a group index and an offset within that group, rather than encoding the absolute position directly. This segmentation reduces the number of bits required to represent the position information.
Solution Approach 2:
The position encoding is transformed from a one-dimensional absolute position index to a two-dimensional representation consisting of a group index and an offset within the group. This dimensional change allows for more efficient compression by exploiting the statistical properties of coefficient distributions across different regions of the transform block.
2Loss of information
If the last non-zero coefficient position is explicitly encoded, then the position information is preserved, but the bitstream requires more bits and processing resources
Solution Approach 1:
By segmenting the transform block into groups of consecutive scan positions and only encoding the group containing the last non-zero coefficient along with an offset, the patent reduces the amount of data that needs to be processed and transmitted while maintaining complete position information accuracy for reconstruction.
Solution Approach 2:
Instead of encoding information for all positions in the transform block, the patent applies partial action by only encoding the relevant group and offset where the last non-zero coefficient is located, thereby reducing computational resources and bitstream size without losing necessary position information.
Data Source
AI summary
An apparatus for decoding a transform block that is decoded using a scan order includes a processor that is configured to decode, from an encoded bitstream, a first syntax element indicating a group of consecutive scan positions in the scan order, where the group of consecutive scan positions includes a scan position of a last non-zero coefficient; determine an offset within the group of consecutive scan positions of the last non-zero coefficient; and decode, from the encoded bitstream, coefficients up to the last non-zero coefficient of the transform block.