Early Slice Cap Decision in Video Encoding Pipeline
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Solution Overview
Problem
In real-time video encoding on embedded systems, the decision to cap a slice is typically made after entropy coding, leading to increased overhead and potential re-processing of macroblocks, which can result in wasted hardware cycles and increased encoding time, making it difficult to achieve real-time encoding.
Innovation Solution
Making the slice cap decision at an earlier stage in the pipeline, specifically during the prediction mode decision, using an adaptive macroblock size estimation model that considers rate distortion cost, quantization step size, and size estimation parameters to estimate the encoded size of macroblocks and determine when to start a new slice before entropy coding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If slice cap decision is made after entropy coding, then the encoded size is accurately known, but pipeline overhead increases and re-processing is required
Solution Approach 1:
The patent applies preliminary action by making the slice cap decision before the entropy coding stage completes. The encoder estimates the encoded size of macroblocks during earlier processing stages (prediction mode decision) and uses this estimation to determine slice boundaries proactively, rather than waiting for the entropy coding to finish and then reacting to the actual size. This prevents the need for re-processing and reduces pipeline overhead by avoiding retroactive slice cap adjustments.
2Measurement precision
If slice cap decision is made after entropy coding, then accurate size information is available, but hardware cycles are wasted due to re-processing
Solution Approach 1:
The patent uses preliminary action to perform slice cap decisions before the entropy coding stage. By estimating macroblock encoded sizes during the prediction mode decision stage and making slice boundary decisions at that time, the system avoids the need to re-process macroblocks later when the actual encoded size is known. This proactive approach eliminates wasted hardware cycles that would otherwise be spent on re-processing due to retroactive slice cap corrections.
3Productivity
If slice cap decision is made earlier in the pipeline, then encoding speed increases, but estimation accuracy may decrease
Solution Approach 1:
The patent applies feedback by continuously monitoring and adjusting the size estimation parameters based on actual encoded sizes from previously processed macroblocks. The encoder maintains a database of actual encoded sizes and uses this feedback information to refine and improve the accuracy of future size estimates. This feedback mechanism allows the system to make accurate slice cap decisions earlier in the pipeline without sacrificing estimation precision, as the estimation model becomes progressively more accurate through feedback from actual encoding results.
Data Source
AI summary
A method for making a slice cap decision during encoding of a video sequence in a video encoding pipe is provided that includes determining a prediction mode for a macroblock, computing an estimated encoded size of the macroblock based on an adaptive macroblock size estimation model, and making a slice cap decision for a current slice based on the estimated encoded macroblock size, wherein the slice cap decision is made prior to entropy coding the macroblock.