Video Coding Mode Selection Parallelization
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Solution Overview
Problem
The complexity of intra coding in video compression standards like MPEG-4 AVC, particularly in real-time applications, leads to processing time issues due to the large number of coding modes that need to be tested sequentially, causing delays in hardware implementation.
Innovation Solution
A method that breaks down the selection of coding modes into two sequential steps: preselecting an intra coding mode during the coding decision process for the current macroblock and then selecting the inter mode, allowing for parallelization of decision processes and reducing causality links between macroblocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intra coding modes are tested sequentially for each macroblock, then coding quality is maintained, but processing time increases significantly
Solution Approach 1:
The patent performs preliminary intra mode selection for all macroblocks before final coding decisions. During this first pass, the encoder evaluates all intra prediction modes for each macroblock and stores the best candidate, without waiting for adjacent macroblocks to be processed. This preliminary action breaks the sequential causality chain, allowing parallel processing while maintaining the quality of intra mode selection.
Solution Approach 2:
The coding process is segmented into two distinct passes: a first pass that performs intra mode preselection for all macroblocks independently, and a second pass that makes final inter/intra mode decisions. This segmentation allows the computationally intensive intra mode evaluation to be performed in parallel across all macroblocks, significantly reducing processing time while preserving coding quality through the subsequent refinement pass.
2Measurement precision
If all intra coding modes are evaluated for each macroblock, then optimal coding mode is selected, but device complexity increases
Solution Approach 1:
The complex mode selection process is segmented into two passes: first pass evaluates all intra modes and identifies best candidates, second pass makes final inter/intra decisions. This segmentation distributes the computational complexity across two simpler stages rather than requiring all decisions to be made simultaneously, reducing peak device complexity while maintaining selection accuracy.
Solution Approach 2:
The first pass performs preliminary evaluation of all intra prediction modes for each macroblock, storing the best candidate without making final coding decisions. This preliminary action simplifies the second pass by reducing the number of modes that need to be compared against inter modes, thereby reducing device complexity while maintaining the accuracy of optimal mode selection.
3Productivity
If intra coding decision is made in real-time context, then processing speed improves, but causality constraints limit parallelization
Solution Approach 1:
The patent performs preliminary intra mode selection for all macroblocks in the current picture before final coding decisions are made. This preliminary action is performed in a context that ignores causality constraints, allowing full parallelization. The results are then used in the second pass where causality is properly respected, enabling real-time processing without sacrificing correctness.
Solution Approach 2:
The first pass intra mode selection acts as an intermediary step that decouples the parallel evaluation of intra modes from the sequential requirements of final coding decisions. This intermediary pass stores preliminary results that can be efficiently used in the second pass, managing the causality constraints while enabling parallel processing and improving productivity.
Data Source
AI summary
The method is characterized in that the step for selecting a coding mode from the inter modes and from the intra modes is broken down into two sequential steps, a step for preselecting the intra coding mode for preselecting an intra mode for the current macroblock from the intra coding modes, and a coding decision step, part of the effective coding of the current macroblock for selecting the mode of coding the current macroblock from the inter modes and the preselected intra mode and in that the preselection step for the current macroblock is carried out during the coding decision step for a preceding macroblock.