Video Quantizer Scale Switching for Stable Inter-Frame Coding
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Solution Overview
Problem
Conventional moving picture coding apparatuses experience hunting in code amounts generated after intra-coded frames, leading to unstable image quality due to inconsistent quantizer scale determination for inter-coded frames.
Innovation Solution
A moving picture coding apparatus that selectively uses different methods to determine quantizer scales based on the coding type of preceding frames, adjusting the quantizer scale for the next frame to prevent drastic changes in code amounts, thereby stabilizing the image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed quantizer scale is used for intra-coded frames to ensure sufficient code amount, then image quality is improved, but hunting in code amounts occurs in subsequent inter-coded frames leading to unstable image quality
Solution Approach 1:
The patent applies dynamics by making the quantizer scale determination method adaptive based on the coding type of the previous frame. When the previous frame is intra-coded, a second method is used that prevents excessive code amount suppression, while when the previous frame is inter-coded, a first method is used for normal adaptation. This dynamic switching eliminates hunting in code amounts while maintaining image quality.
Solution Approach 2:
The patent changes the parameter of quantizer scale determination by introducing two different determination methods. The first method uses standard adaptive quantizer scale adjustment, while the second method modifies the adjustment to prevent excessive suppression after intra-coded frames. This parameter change resolves the contradiction by maintaining appropriate code amounts in both scenarios.
2Productivity
If the quantizer scale is increased to提高 compression rate, then code size is reduced, but image quality deteriorates due to unstable code amount control
Solution Approach 1:
The patent applies dynamics by making the quantizer scale determination adaptive based on the previous frame's coding type. This prevents the hunting phenomenon that causes image quality instability, thereby maintaining consistent image quality while achieving efficient compression through appropriate quantizer scale selection.
Solution Approach 2:
The patent uses feedback by determining the quantizer scale for the current frame based on the code amount of the previous frame. The determination method adapts according to whether the previous frame was intra-coded or inter-coded, providing feedback control that stabilizes code amounts and maintains image quality while improving compression efficiency.
3Adaptability or versatility
If adaptive quantizer scale determination is used for each frame to control code amount, then code amount adaptation is improved, but hunting in code amounts occurs after intra-coded frames causing image quality instability
Solution Approach 1:
The patent applies dynamics by making the quantizer scale determination method switchable based on the previous frame's coding type. This dynamic adaptation maintains code amount control effectiveness while preventing hunting instability, thereby achieving both adaptability and stability.
Solution Approach 2:
The patent applies local quality by using different quantizer scale determination methods for different situations. The first method is used when the previous frame is inter-coded, while the second method is used when the previous frame is intra-coded. This localized approach optimizes code amount control for each specific context, preventing hunting while maintaining adaptability.
Data Source
AI summary
When a frame (n+1) is to be inter-coded after inter-coding a frame n (S142: INTER), a moving picture coding apparatus determines a quantizer scale Q[n+1] to be used in quantization of the frame (n+1), using a first method, based on an amount of generated codes Cn of the frame n (S143). When the frame (n+1) is to be inter-coded after intra-coding the frame n (S142: INTRA), the moving picture coding apparatus determines the quantizer scale Q[n+1] to be used in quantization of the frame (n+1), using a second method, based on the amount of generated codes Cn of the frame n (S143). The quantizer scale determined by using the second method takes a smaller value than that determined by using the first method.