Adaptive Video Coding Structure and FCode Selection
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Solution Overview
Problem
Video encoders face challenges in determining the optimal coding structure and fixed code (fcodes) for motion vectors, leading to quality degradation and increased overhead, especially at high motion sequences, due to the sequence-dependent nature of coding structures and the complexity of variance-based fcode selection methods.
Innovation Solution
Adaptive coding structure determination and fcode selection methods are implemented, where the coding structure for consecutive frames is chosen based on the level of motion in preceding frames, and fcode is adjusted using low-complexity motion vector histograms to optimize quality and reduce hardware complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed coding structure (e.g., IPPP, IBBP) is used, then the encoding process is simple and consistent, but the quality varies significantly depending on the sequence-dependent motion characteristics
Solution Approach 1:
The patent applies dynamics by transitioning from fixed coding structures to adaptive coding structures that change based on motion characteristics. The encoder dynamically selects coding structures (e.g., switching between IPPP and IBBP) according to the motion variance calculated for different frame sequences, allowing the system to adapt to varying motion patterns while maintaining operational simplicity through automated selection criteria.
2Manufacturing precision
If fcode is increased to expand motion vector search range, then quality improves for high motion sequences, but large fixed overhead is incurred leading to rate-distortion degradation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the fcode parameter based on motion variance calculations. Instead of using a fixed high fcode value that increases overhead, the encoder calculates motion variance for each sequence and selects appropriate fcode values (e.g., fcode=1 for low motion, fcode=3 for high motion), optimizing the balance between search range coverage and bitstream efficiency.
Solution Approach 2:
The patent applies local quality by applying different fcode values to different frame sequences based on their specific motion characteristics. Rather than using a uniform high fcode for all sequences, the encoder selectively applies higher fcode values only to sequences with high motion variance, while using lower fcode values for sequences with low motion, thereby optimizing quality where needed while minimizing overhead elsewhere.
3Manufacturing precision
If variance-based fcode selection is used to handle motion issues, then quality is maintained across different motion levels, but hardware complexity increases due to expensive multiplication operations
Solution Approach 1:
The patent applies mechanics substitution by replacing the computationally intensive variance calculation (which requires multiplication operations) with an alternative motion estimation approach that uses only addition and comparison operations. The encoder uses motion vector differences and absolute value calculations to estimate motion activity, substituting the mechanical multiplication process with simpler arithmetic operations that are less demanding on hardware resources.
Solution Approach 2:
The patent applies this principle by using simplified motion estimation metrics that require minimal computational resources. Instead of performing expensive variance calculations with full precision multiplications, the encoder uses approximations based on motion vector components and absolute differences, which can be computed quickly and discarded after use, reducing the need for complex hardware multiplication units.
Data Source
AI summary
A method of encoding a digital video sequence is provided that includes computing a motion vector (MV) histogram and a motion threshold for a first frame of the digital video sequence, and using the MV histogram and the motion threshold for one selected from a group consisting of adaptive fcode determination and adaptive coding structure determination.