Video Transrating via Dynamic Coefficient Removal
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Solution Overview
Problem
Existing video transrating techniques face challenges in achieving high-quality output with low complexity and bit-rate while maintaining fast adaptation speed, often resulting in visual degradation and artefacts, especially in high motion scenes, due to their complex architectures and lossy processes.
Innovation Solution
A method and apparatus that dynamically disregard a configurable proportion of non-zero transform coefficients for all blocks within a frame, taking into account local motion activity, to generate a transrated output bit stream, which avoids significant degradation and artefacts by uniformly distributing visual impact across frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex transrating architectures with multiple processing stages are used, then output quality can be improved, but system complexity and computational cost increase significantly
Solution Approach 1:
The patent extracts and removes only the least important transform coefficients from each macroblock, rather than processing the entire video stream through complex multiple stages. By identifying and discarding a configurable proportion of non-zero coefficients directly from the compressed bitstream, the system achieves bit-rate reduction with minimal processing complexity, avoiding the need for full decode-recode pipelines.
Solution Approach 2:
The patent applies different processing to different parts of the video data by treating I-frames and P-frames differently. I-frames are processed with one coefficient removal ratio while P-frames use a different ratio, allowing local optimization of quality versus bit-rate reduction based on the specific frame type and its importance to video reconstruction.
2Quantity of substance
If aggressive bit-rate reduction is applied, then output bit-rate decreases, but visual quality and adaptation speed deteriorate
Solution Approach 1:
The patent employs dynamic adaptation by adjusting the proportion of coefficients removed based on the specific frame type (I-frame or P-frame) and instantaneous bit-rate requirements. The system can dynamically change the coefficient removal ratio to achieve target bit-rates while maintaining acceptable quality, rather than applying a fixed aggressive reduction that would always degrade quality.
Solution Approach 2:
The system changes the parameter of coefficient removal ratio dynamically based on frame type and bit-rate targets. By modifying this single parameter rather than fundamentally changing the processing architecture, the system achieves adaptive bit-rate control that balances quality and compression efficiency without requiring complex multiple processing stages.
3Device complexity
If uniform coefficient removal is applied across all blocks, then system complexity is reduced, but local motion activity is not adequately preserved
Solution Approach 1:
The patent applies different coefficient removal ratios to different frame types (I-frames versus P-frames) based on their local characteristics and importance to motion representation. This local differentiation allows the system to preserve motion information in P-frames more aggressively while maintaining higher quality in reference I-frames, achieving better motion preservation without requiring block-by-block analysis.
Data Source
AI summary
The invention provides a method of transcoding a video signal made up of an input bit stream representative of frames of a video, each frame being made up of blocks of pixels, there being a corresponding block of data within the input bit stream for each block of pixels, the method comprising: for the bit stream of a frame of the video signal, identifying the type of frame; and for certain types of frame, disregarding a configurable proportion of the data in respect of plural blocks within the frame, thereby taking into account local motion activity within the frame.