Adaptive Intra Refresh Encoding for Bitrate Spike Reduction
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Solution Overview
Problem
H.264 encoding and similar standards face a significant bitrate spike due to large I-frame vs P-frame size ratios, particularly in surveillance systems, leading to an undesirable bitrate penalty when using periodic intra refresh to spread I-frames across multiple frames.
Innovation Solution
A method dynamically selects the size of the intra encoding region based on the level of motion in the image frame, adjusting the intra refresh padding by expanding the intra encoding region when motion exceeds a threshold to minimize bitrate penalties, allowing for efficient encoding of I-blocks and P-blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic intra refresh is used to spread I-frames across multiple frames, then the bitrate spike problem is reduced, but a bitrate penalty is incurred due to unnecessary I-block encoding
Solution Approach 1:
The patent applies dynamics by making the intra refresh region size adaptive rather than fixed. The encoder dynamically adjusts the size of the intra refresh region based on the detected motion level in the current frame. When motion is low, a smaller region is used; when motion is high, a larger region is used. This dynamic adaptation resolves the contradiction by optimizing the balance between bitrate stability and bitrate penalty based on actual scene conditions.
Solution Approach 2:
The patent changes the parameter of intra refresh region size based on motion level. By monitoring motion estimation results and adjusting the intra refresh region size accordingly, the system transforms a static parameter into a dynamic one that adapts to scene content. This parameter change allows the system to minimize bitrate penalty while maintaining bitrate stability through selective intra encoding.
2Reliability
If the intra refresh region is expanded to overlap with previously encoded regions, then block matching algorithm performance is improved, but encoding efficiency decreases
Solution Approach 1:
The patent applies local quality by differentiating the encoding approach for different regions of the frame. Instead of uniformly expanding the intra refresh region, the system selectively expands it only in areas where motion detection indicates it is necessary. This local adaptation ensures that block matching performance is improved only where needed, while preserving encoding efficiency in regions where motion is minimal.
Solution Approach 2:
The patent implements partial action by applying intra refresh region expansion only partially - specifically in regions where motion exceeds a certain threshold. Rather than expanding the intra refresh region uniformly across the entire frame, the system applies the expansion selectively to local areas, thereby achieving improved block matching performance only where necessary while maintaining overall encoding efficiency.
Data Source
AI summary
Video encoding is provided using periodic intra refresh, which can adapt padding of an intra encoding region between image frames based on a current level motion in the image frame. Upon a current level of motion not exceeding a first threshold, an intra encoding region of the image frame according to a predefined periodic intra refresh pattern is intra encoded. Upon the current level of motion exceeding the first threshold, the intra encoding region of the image frame is expanded to overlap to a determined extent with a previously encoded intra encoding region among the plurality of image frames, and the expanded intra encoding region of the image frame is intra encoded. Regions of the image different from the intra encoding regions and the expanded intra encoded region, respectively are inter frame encoded.