Adaptive Intra Refresh Macroblock Selection for Video Coding
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Solution Overview
Problem
Intra refresh (IR) in video encoding leads to a degradation in perceived signal to noise ratio (PSNR) due to inefficient coding of macroblocks, particularly in low motion video sequences, resulting in poor subjective quality and increased bit consumption.
Innovation Solution
Selecting macroblocks for intra coding based on a correlation between differential RD cost and Inter RD cost, with a penalty factor to adjust bit costs, and ensuring that at least a predetermined number of macroblocks are intra coded in each frame, while maintaining error concealment capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Intra refresh is applied to ensure error concealment capability, then reliability is improved, but manufacturing precision deteriorates due to forced Intra coding of macroblocks that would be better suited for Inter coding
Solution Approach 1:
The patent applies different coding strategies to different macroblocks based on their local characteristics. Motion estimation is performed selectively on macroblocks that benefit from temporal redundancy, while other macroblocks use Intra coding for error resilience. This localized approach optimizes each macroblock's coding mode based on its specific needs rather than applying a uniform strategy.
Solution Approach 2:
The patent dynamically adjusts the Intra refresh pattern based on motion activity in the video sequence. The refresh interval and macroblock selection are adapted according to measured motion characteristics, allowing the system to optimize between error concealment and coding efficiency for different scene conditions rather than using a fixed pattern.
2Reliability
If a fixed number of Intra macroblocks are coded in each frame according to cyclic or random patterns, then error concealment is maintained, but productivity deteriorates due to increased bit consumption
Solution Approach 1:
The patent changes the parameters governing macroblock selection for Intra coding from fixed cyclic or random patterns to adaptive parameters based on motion estimation results. The selection criteria include motion magnitude, motion direction, and temporal redundancy measures, allowing the system to identify and Intra-code only those macroblocks that require error protection while maintaining good compression efficiency.
3Reliability
If macroblocks with low residual energy are Intra coded due to IR constraints, then error concealment is improved, but loss of information increases due to inefficient bit usage
Solution Approach 1:
The patent incorporates feedback mechanisms where motion estimation results from previously coded macroblocks influence the coding decisions for subsequent macroblocks. The system uses measured motion characteristics and residual energy patterns to adaptively adjust the Intra/Inter coding decisions, ensuring that macroblocks are coded in the most efficient mode while maintaining error concealment where needed.
Data Source
AI summary
A method of video coding comprising Intra prediction coding at least a predetermined constant M macroblocks within an ordinary frame. These M macroblocks include naturally selected macroblocks where the bit cost of Intra prediction coding is less than for Inter prediction coding and optional additional macroblocks. The optional additional macroblocks have the least bit cost of Inter prediction coding as adjusted by a penalty factor each time a corresponding macroblock is Intra coded in a predetermined number of frames. An end frame Intra prediction codes each macroblock having no corresponding Intra prediction coded macroblock in a predetermined number of ordinary frames.