4x4 DCT Transform Factor Extraction for Video Coding Gain
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Solution Overview
Problem
Conventional 4×4 discrete cosine transform (DCT) implementations in video compression techniques face limitations in achieving optimal coding gain due to increased implementation complexity and noise introduction, particularly in power-sensitive devices and real-world coding pipelines.
Innovation Solution
The implementation of orthogonal and near-orthogonal 4×4 DCTs with specific internal and scaled factors, such as those defined by equations involving ξ=C+Sω+ψ or ξ=A+B+1/2, which reduce implementation complexity by removing internal factors and incorporating external factors in quantization, enhancing coding gain while maintaining invertibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional 4×4 DCT implementations are used, then coding gain can be achieved, but implementation complexity increases and noise is introduced
Solution Approach 1:
The patent extracts and removes internal factors from the conventional 4×4 DCT implementation, keeping only the scaled factors. This extraction reduces implementation complexity by eliminating unnecessary computational elements while preserving the essential transform functionality and coding gain through the retained scaled factors.
Solution Approach 2:
The patent changes the parameters of the DCT implementation by defining specific relationships between scaled factors and internal factors through equations (such as ξ=C+Sω+ψ or ξ=A+B+1/2). These parameter changes optimize the transform to reduce complexity while maintaining or improving coding gain through carefully selected factor values.
2Reliability
If conventional 4×4 DCT implementations are used, then transform functionality is maintained, but noise is introduced in power-sensitive devices
Solution Approach 1:
By removing internal factors from the DCT implementation, the patent reduces the number of computational operations required, thereby lowering power consumption in power-sensitive devices. The extraction process eliminates redundant calculations that contribute to noise while preserving the core transform functionality needed for reliable coding.
Solution Approach 2:
The patent employs simplified factor relationships that can be implemented with lower computational resources, effectively using simpler, less resource-intensive mathematical operations to achieve the transform. This approach reduces power consumption and associated noise generation while maintaining adequate coding performance.
3Device complexity
If internal factors are removed and external factors are incorporated in quantization, then implementation complexity is reduced, but transform accuracy may be affected
Solution Approach 1:
The patent carefully defines parameter relationships through specific equations that govern the connection between scaled factors and internal factors. These parameter changes are designed to maintain transform accuracy by ensuring that the simplified implementation with removed internal factors still produces results within acceptable precision boundaries through optimized scaled factor selection.
Solution Approach 2:
The scaled factors serve as intermediaries that bridge the gap between the removed internal factors and the quantization process. By incorporating these scaled factors into the quantization stage, the patent maintains transform accuracy despite the removal of internal factors, as the scaled factors carry the necessary information through the simplified implementation pipeline.
Data Source
AI summary
In general, techniques are described that provide for 4×4 transforms for media coding. A number of different 4×4 transforms are described that adhere to these techniques. As one example, an apparatus includes a 4×4 discrete cosine transform (DCT) hardware unit. The DCT hardware unit implements an orthogonal 4×4 DCT having an odd portion that applies first and second internal factors (C, S) that are related to a scaled factor (ξ) such that the scaled factor equals a square root of a sum of a square of the first internal factor (C) plus a square of the second internal factor (S). The 4×4 DCT hardware unit applies the 4×4 DCT implementation to media data to transform the media data from a spatial domain to a frequency domain. As another example, an apparatus implements a non-orthogonal 4×4 DCT to improve coding gain.