Motion-Adaptive Intra-Refresh for Low-Latency Video Coding
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Solution Overview
Problem
Conventional intra-refresh modes in video coding experience significant bit rate variation and latency issues due to global motion in virtual reality and augmented reality applications, where the shifting position of the refresh region often leads to inefficient encoding and higher transmission latency.
Innovation Solution
A motion-adaptive intra-refresh mode is implemented, where the refresh region is fixed to the edge of the picture in the direction of global motion, allowing for efficient encoding by aligning the refresh region with the introduction of new content, thereby reducing bit rate variability and improving encoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refresh region shifts positions between successive pictures in conventional intra-refresh modes, then the goal of smoothing out bitrate is achieved, but significant bit rate variation and jitter occur in the presence of global motion
Solution Approach 1:
Instead of shifting the refresh region in the conventional direction, the patent inverts the approach by fixing the refresh region at the picture edge in the direction of global motion. This inversion allows the clean region to naturally shift opposite to the global motion direction, achieving bitrate smoothing without the harmful jitter caused by conventional shifting methods.
Solution Approach 2:
The patent changes the parameter of refresh region positioning from a dynamic shifting pattern to a fixed edge position. By fixing the refresh region at the picture edge corresponding to the global motion direction, the encoding system adapts to global motion conditions while maintaining stable bitrate characteristics.
2Productivity
If the refresh region is fixed at the picture edge in the direction of global motion, then encoding efficiency is improved and bit rate variability is reduced, but the region must be entirely intra-coded which increases bit consumption
Solution Approach 1:
The patent applies local quality by differentiating the encoding approach for different regions: the refresh region at the picture edge is entirely intra-coded to handle new content introduction, while the clean region uses efficient inter-coding with motion predictions. This localized strategy optimizes bit consumption by applying the appropriate encoding method to each region's specific requirements.
Solution Approach 2:
The refresh region is positioned at the picture edge in advance, before encoding begins, to preemptively handle the introduction of new content. This preliminary positioning ensures that regions requiring intra-coding are identified and processed beforehand, improving overall encoding efficiency and reducing bit rate variability.
3Reliability
If motion predictions are restricted to clean regions only, then error propagation is prevented, but the coding of I-pictures takes significantly more bits impacting bit rate and latency
Solution Approach 1:
The patent segments the picture into two distinct regions: the refresh region that is entirely intra-coded to prevent error propagation, and the clean region that uses inter-coding with motion predictions. This segmentation allows the system to maintain reliability in the refresh region while reducing latency and bit consumption in the clean region through efficient predictive coding.
Solution Approach 2:
Instead of applying intra-coding to the entire picture, the patent applies intra-coding only partially to the refresh region at the picture edge. This partial action approach prevents error propagation where necessary while avoiding the excessive bit consumption and latency that would result from fully intra-coding the entire picture.
Data Source
AI summary
A method includes intra-refresh encoding each picture of a first set of pictures such that a position of a refresh region for the picture is spatially shifted relative to the position of the refresh region for a previous picture of the first set responsive to determining global motion associated with the first does not exceed a specified threshold. The method further includes intra-refresh encoding each picture of a second set of pictures such that a position of a refresh region for each picture of the second set is fixed to be immediately adjacent to a picture edge that is in a direction of global motion associated with the second set responsive to determining the global motion associated with the second set exceeds the specified threshold.