Block-Based Rate Control for Low Latency Video Encoding
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Solution Overview
Problem
Virtual reality (VR) and mixed reality (MR) systems face challenges in encoding high-resolution video at low latencies for wireless transmission, requiring efficient rate control methods to manage bandwidth and maintain quality under varying channel conditions.
Innovation Solution
A video encoding system employing a wavelet transform and block-based encoding with a rate control component that adjusts quantization parameters for each block, using rate-distortion curves and complexity metrics to optimize bandwidth usage and video quality, minimizing wavelet-inverse distortion while meeting rate bounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If rate control is performed at frame or strip level, then the encoder can adjust quantization parameters more smoothly, but the latency increases and memory requirements grow
Solution Approach 1:
The patent divides the frame into blocks and applies rate control at the block level rather than at the frame or strip level. This segmentation allows the encoder to adjust quantization parameters independently for each block, reducing the memory buffer requirements and latency while maintaining smooth quality transitions through coordinated block-level rate control.
2Manufacturing precision
If high-resolution video is encoded at low latency, then the transmission quality is maintained, but the bandwidth consumption increases
Solution Approach 1:
The patent applies different quantization parameters to different blocks within a frame based on their local characteristics and importance. This allows the encoder to allocate bits more efficiently, maintaining high quality for important regions while reducing compression for less critical areas, thereby reducing overall bandwidth consumption while preserving video quality.
3Adaptability or versatility
If quantization parameters are adjusted frequently to adapt to channel conditions, then the bandwidth utilization is optimized, but the distortion increases
Solution Approach 1:
The patent implements a feedback mechanism where the encoder monitors channel conditions and adjusts quantization parameters accordingly. The rate control component uses feedback about actual bitrates and distortion metrics to dynamically adapt quantization parameters for each block, optimizing bandwidth utilization while minimizing distortion through coordinated adjustment across multiple blocks.
Data Source
AI summary
Block-based, low latency rate control for an encoding system in which a wavelet transform decomposes pixel blocks into subbands stored as subbands in wavelet blocks (WBs) for encoding. Quantization parameters (QPs) for the subbands in each WB are estimated using a method that minimizes wavelet-inverse distortion given a rate bound. For each subband, a rate curve is generated based on an unquantized DCT histogram and bit count statistics for the subband, and a distortion curve is generated based on the unquantized DCT histogram and a distortion estimate for the subband that is estimated using a masked estimator. Once the rate-distortion curves for the subbands are generated, a bisection search may be used to find a point on each curve where the slope is the same for all the curves. The QPs associated with those equally sloped points are the global minimizing QPs for the wavelet block.