Hybrid Encoding Parameter Order Determination
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Solution Overview
Problem
Current hybrid video encoding schemes, such as H.264/AVC, face challenges in optimizing encoding parameters across frames due to dependent rate-distortion behavior, leading to an exponentially growing search space and inefficient bit allocation, making it difficult to achieve optimal compression rate-distortion trade-offs.
Innovation Solution
A method that combines multipass encoding and rate-distortion optimization by pre-encoding frames with different quantization parameter orders, using a tree structure to determine the optimum order of quantization parameters, which reduces the complexity of evaluating all possible combinations and focuses on the quality of previous frames to estimate distortion and compression rates for subsequent frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If frame-to-frame rate-distortion optimization is performed in hybrid encoding schemes, then encoding complexity and computational burden are reduced, but the compression rate-distortion trade-off becomes suboptimal due to ignoring inter-frame dependencies
Solution Approach 1:
The patent segments the frame sequence into groups of pictures (GOPs) and performs optimization at the GOP level rather than individual frame level. This segmentation allows considering inter-frame dependencies within the GOP while limiting the optimization scope to manageable segments, thus balancing computational complexity with optimization quality.
Solution Approach 2:
The patent performs preliminary rate-distortion optimization for all frames in a GOP before actual encoding. This preliminary action includes calculating RD costs for all possible quantization parameter combinations across the GOP, determining the optimal QP sequence in advance, and then using this pre-determined sequence for actual encoding, which avoids repeated complex calculations during real-time encoding.
2Manufacturing precision
If all possible quantization parameter combinations are evaluated across frames, then optimal compression rate-distortion trade-off is achieved, but the search space grows exponentially
Solution Approach 1:
The patent applies different quantization parameter optimization strategies to different regions of the GOP structure. Intra-coded frames (I-frames) are optimized independently with full QP selection freedom, while predictive-coded frames (P-frames and B-frames) have their QP selection constrained by reference frame quality requirements. This local differentiation reduces the overall search space while maintaining optimal RD trade-offs in each region.
Solution Approach 2:
Instead of evaluating all possible QP combinations across the entire video sequence, the patent performs exhaustive evaluation only within limited GOP segments. The optimization is applied partially to manageable portions of the video stream, using dynamic programming to find optimal paths through the reduced search space, rather than attempting exhaustive search over the complete sequence.
3Productivity
If multipass encoding is used to distribute bits intelligently across frames, then bit allocation improves, but rate-distortion optimization is not achieved
Solution Approach 1:
The patent incorporates feedback mechanisms where the RD cost calculations for each frame consider the impact of QP selection on subsequent frames in the GOP. The optimization process uses feedback from reference frame quality assessments to adjust QP selections for predictive frames, ensuring that bit allocation decisions account for both current frame quality and future frame dependencies, thereby achieving true RD optimization rather than simple bit distribution.
Data Source
AI summary
A method for determining an order of values for an encoding parameter of a hybrid encoding scheme for each frame of a frame sequence for use for encoding the frame sequence by means of the hybrid encoding scheme is described. Using the hybrid encoding scheme, resulting distortions and compression rates for the frames of the frame sequence are established for the case of the complete encoding of the frame sequence, and for the case of the incomplete encoding of a real partial sequence of the frame sequence. Thereupon, establishing of estimated distortions and compression rates for frames of the frame sequence takes place, followed by determining the order of values for the encoding parameter of the hybrid encoding scheme based on the established resulting and estimated distortions and compression rates.