Dynamic Transform Size Selection in Video Decoders
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Solution Overview
Problem
Existing video compression technologies, such as the H.264 standard, face challenges in achieving low bit-rate compression without producing visible compression artifacts, particularly in areas with sharp transitions, as increasing transform size to improve efficiency can result in noticeable artifacts.
Innovation Solution
A method and system for dynamically selecting transform size based on signal content, using simplified selection rules and guidelines that combine the benefits of reduced residual correlation with large transform sizes in areas without high detail or sharp transitions, thereby minimizing artifacts and improving compression efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transform size is increased to improve compression efficiency, then coding efficiency is improved, but compression artifacts become more visible in areas with sharp transitions
Solution Approach 1:
The patent applies different transform sizes to different regions of the image based on their content characteristics. Smooth regions use larger transforms for better compression efficiency, while regions with sharp transitions use smaller transforms to minimize artifacts. This local adaptation resolves the contradiction by making the transform size context-dependent rather than uniform.
Solution Approach 2:
The patent dynamically selects transform sizes based on the detected signal content in each macroblock. The transform size is not fixed but adapts according to the local characteristics of the video signal, allowing the system to optimize between compression efficiency and artifact minimization in real-time during encoding.
2Loss of energy
If transform size is increased to reduce residual correlation, then signal energy compaction is improved, but implementation complexity increases
Solution Approach 1:
The patent divides the image into macroblocks and further into smaller blocks within macroblocks, applying different transform sizes to each segment based on its content. This segmentation allows the system to achieve good energy compaction in smooth regions without applying large transforms throughout the entire image, thus reducing overall implementation complexity.
Solution Approach 2:
The patent changes the transform size parameter dynamically based on the detected characteristics of each macroblock. By adjusting this single critical parameter according to local signal content, the system achieves effective energy compaction without requiring complex multi-parameter optimization or multiple transform types, simplifying the overall implementation.
Data Source
AI summary
In a video processing system, a method and system for dynamic selection of transform size in a video decoder based on signal content are provided. For high profile mode video decoding operations, inverse transform sizes may be selected from a 4×4 or an 8×8 inverse transform size based on a transform size syntax element generated by the encoding operation and transmitted as part of the encoded video information bit stream. A set of rules is defined for selecting the transform size based on a macroblock type and a size of the macroblock type of a received macroblock in a video decoder. Dynamic selection of transform size may be performed on intra-coded macroblocks, inter-coded macroblocks, and/or direct mode inter-coded macroblocks.