Unified DCT Transform Architecture for Large-Block Video Coding
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Solution Overview
Problem
Existing video coding standards, such as HEVC, face challenges with high implementation complexity due to large block size transforms and directional transforms, which are not efficiently implementable in hardware and software environments.
Innovation Solution
A transform and quantization architecture that uses a unified DCT matrix for various block sizes, reducing the need for separate matrices and enabling efficient implementation in hardware and software through configurable DCT and IDCT operations, along with reduced memory requirements for norm correction matrices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large block size transforms (16×16, 32×32, 64×64 DCT) and directional transforms are used, then coding efficiency is improved, but implementation complexity increases significantly
Solution Approach 1:
The patent segments the transform process by separating the transform coefficient generation from the transform matrix multiplication. The residual block is first transformed to generate transform coefficients, and then the transform matrix is applied separately. This segmentation allows for optimized implementation of each stage, reducing overall complexity while maintaining coding efficiency.
Solution Approach 2:
The patent changes the parameter representation by using scaled transform coefficients and pre-computed transform matrices with specific scaling factors. The transform matrices are designed with embedded scaling to eliminate separate normalization steps, reducing computational complexity. The use of integer-based arithmetic with carefully chosen scaling parameters enables efficient hardware implementation without loss of precision.
2Manufacturing precision
If separate transform matrices are used for various block sizes, then transform accuracy is maintained, but memory requirements increase
Solution Approach 1:
The patent implements a universal transform matrix that can be applied to multiple block sizes (4×4, 8×8, 16×16, 32×32, 64×64) through parameterized indexing. The same base transform matrix is used for all block sizes by selecting appropriate submatrices and applying scaling factors based on the block size parameter. This universal approach eliminates the need to store separate transform matrices for each block size, significantly reducing memory requirements while maintaining transform accuracy.
3Manufacturing precision
If full matrix multiplication is used for directional transforms, then transform precision is improved, but computational complexity increases
Solution Approach 1:
The patent transforms the full matrix multiplication operation into a parameterized computation using pre-computed directional transform coefficients. Instead of performing complete matrix multiplication, the implementation uses scaled coefficient arrays with specific indexing patterns that encode the directional transform information. This parameterized approach reduces the number of multiplication operations while preserving transform precision through carefully selected scaling factors.
Data Source
AI summary
A method of encoding a video stream in a video encoder is provided that includes computing an offset into a transform matrix based on a transform block size, wherein a size of the transform matrix is larger than the transform block size, and wherein the transform matrix is one selected from a group consisting of a DCT transform matrix and an IDCT transform matrix, and transforming a residual block to generate a DCT coefficient block, wherein the offset is used to select elements of rows and columns of a DCT submatrix of the transform block size from the transform matrix.