HEVC Pre-encoding for Bitrate Control
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Solution Overview
Problem
Existing HEVC encoding technologies face challenges in achieving accurate bitrate control and quality optimization due to high encoding complexity and the inter-dependency between rate distortion optimization and rate control, leading to inefficiencies in bit allocation and quality maintenance, especially during scene changes.
Innovation Solution
The implementation of a pre-encoding process using a reduced set of encoding modes to estimate initial encoding parameters such as λ and QP, which are then adjusted through repeated fast-encodings to refine the encoding process, allowing for improved bitrate control and quality optimization with minimal increase in encoding complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HEVC encoding uses full encoding modes to achieve accurate bitrate control and quality optimization, then encoding quality and bitrate control accuracy are improved, but encoding complexity increases significantly
Solution Approach 1:
The patent applies preliminary action by performing a first pass encoding with a reduced subset of encoding modes before the final encoding pass. This preliminary pass estimates initial encoding parameters (λ and QP) that are then used to guide the full encoding process, allowing the system to achieve accurate bitrate control without examining all possible encoding modes from the start, thus reducing overall encoding complexity while maintaining precision.
Solution Approach 2:
The encoding process is segmented into multiple passes: a first pass using a reduced subset of encoding modes to estimate parameters, and subsequent passes using the full set of encoding modes with refined parameters. This segmentation allows the system to divide the complex encoding task into manageable stages, reducing the computational burden in any single pass while achieving overall high precision.
2Productivity
If HEVC encoding uses reduced subset of encoding modes to reduce encoding complexity, then encoding time is reduced, but bitrate control accuracy and quality deteriorate
Solution Approach 1:
The reduced subset encoding is performed as a preliminary action to estimate initial parameters quickly, not as the final encoding. This allows the system to benefit from the speed of reduced-mode encoding while subsequently refining the results using full encoding modes with adjusted parameters, thus achieving both high encoding speed and accurate bitrate control.
Solution Approach 2:
The patent implements feedback by using the results from the reduced subset encoding pass to adjust and refine encoding parameters for subsequent full encoding passes. The initial parameter estimates from the fast pass feed into the final encoding process, allowing the system to correct any inaccuracies introduced by the reduced-mode approximation and achieve precise bitrate control.
3Measurement precision
If HEVC encoding performs repeated fast-encodings to adjust encoding parameters, then bitrate control accuracy is improved, but encoding complexity increases
Solution Approach 1:
Repeated fast-encodings are performed as preliminary actions to iteratively refine parameter estimates before the final encoding pass. Each fast-encoding pass provides feedback that adjusts the parameters for the next pass, converging toward optimal values without requiring multiple full-complexity encoding passes, thus achieving high parameter accuracy with controlled complexity increase.
4Manufacturing precision
If HEVC encoding uses full set of encoding modes to optimize quality, then video quality is improved, but encoding time increases
Solution Approach 1:
The encoding process is segmented into a fast preliminary pass with reduced modes and a final quality-optimization pass with full modes. This segmentation allows the system to spend minimal time on initial parameter estimation and concentrate computational resources on the final pass where high video quality is achieved, thus optimizing the trade-off between encoding time and video quality.
Solution Approach 2:
The reduced-mode encoding serves as a preliminary action that prepares optimal parameters for the final encoding pass. By pre-calculating and adjusting parameters using the fast pass, the system minimizes the time required for the quality-critical final pass, achieving high video quality with reduced total encoding time.
Data Source
AI summary
An HEVC encoder is described that utilizes pre-compression, or pre-encoding, to improve the rate control at a relatively small increase in computational complexity.