Video Signal Coding Luminance Chrominance Rate Control
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Solution Overview
Problem
Conventional video signal coding methods, such as H.264, face challenges in achieving balanced code allocation between luminance and chrominance signals, leading to unbalanced rate control operations and deteriorated subjective image quality, especially when the quantization parameter qP_I is high.
Innovation Solution
A video signal coding apparatus and method that quantizes luminance and chrominance signals using separate quantization matrices, monitors code amounts, and adjusts coefficient values to maintain a balanced rate between luminance and chrominance code amounts, ensuring optimal image quality by changing the quantization matrices based on calculated rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional H.264 rate control is used with high qP_I values, then code amount reduction is achieved, but chrominance code amount becomes disproportionately large relative to luminance code amount
Solution Approach 1:
The patent segments the code amount control into two independent parts: luminance code amount control and chrominance code amount control. By calculating and controlling these separately using different quantization matrices (first for luminance, second for chrominance), the system prevents the chrominance component from consuming excessive code resources while maintaining overall rate control effectiveness.
Solution Approach 2:
The patent applies different quality control strategies to different signal components. The luminance signal receives one level of quantization control while the chrominance signal receives a different level of control, allowing each component to be optimized independently according to its specific characteristics and importance to image quality.
2Manufacturing precision
If separate quantization matrices are used for luminance and chrominance, then code allocation balance is improved, but device complexity increases
Solution Approach 1:
The patent merges the rate control functionality into a unified apparatus that simultaneously handles both luminance and chrominance quantization. The rate control unit integrates code amount calculation, ratio computation, and dual quantization matrix control in one cohesive system, avoiding the need for completely separate control mechanisms.
Solution Approach 2:
The patent changes the quantization parameters (coefficient values in quantization matrices) based on the calculated chrominance-to-luminance code amount ratio. By dynamically adjusting these parameters, the system achieves balanced code allocation without requiring complex structural modifications.
3Ease of manufacture
If chrominance code amount is not controlled, then encoding simplicity is maintained, but subjective image quality deteriorates at low bit rates
Solution Approach 1:
The patent implements a feedback mechanism where the chrominance code amount is calculated based on actual encoding results, the ratio to luminance code amount is computed, and this ratio feeds back to adjust the second quantization matrix. This closed-loop control automatically prevents chrominance from consuming excessive code resources while maintaining encoding efficiency.
Solution Approach 2:
The patent performs preliminary calculation of the chrominance code amount before final encoding decisions are made. By computing the code amount ratio in advance and using it to adjust quantization parameters beforehand, the system proactively prevents image quality deterioration rather than reacting to it after the fact.
Data Source
AI summary
Video signal coding apparatus includes a quantization unit which quantizes a luminance signal of each of a first picture and a second picture coded after the first picture, and quantizes a chrominance signal of each of the first picture and the second picture. A code amount obtainment unit obtains a luminance code amount and a chrominance code amount of each of the first picture and the second picture; and a rate calculation unit calculates a rate of the chrominance code amount with respect to the luminance code amount for each of the first picture and the second picture. A rate control unit changes a coefficient value of at least one of the first matrix and the second matrix used in quantizing the second picture, before the quantization unit quantizes the second picture, so that the rate for the second picture becomes smaller than the rate for the first picture.