Bit Rate Control for Variable Bit Rate Video Coding
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Solution Overview
Problem
Variable bit rate video coding methods, such as those used in MPEG-2, H.264, and MPEG-4, face challenges in maintaining consistent picture quality across different frame types (I-, P-, and B-frames) due to fixed bit rate allocation, leading to potential deterioration in picture quality.
Innovation Solution
A method and apparatus for controlling bit rates in variable bit rate video encoding by calculating a quality measure for each frame and comparing it to the mean of previous frames' measures, adjusting the quantization parameter based on deviations from this mean to maintain consistent picture quality, involving a quality measure calculator, comparator, and quantization parameter setting unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed bit rate is allocated to I-, P-, and B-frames based on picture type, then bit rate control is simplified, but picture quality deteriorates due to inability to adapt to frame-specific characteristics
Solution Approach 1:
The patent applies dynamics by transitioning from fixed bit rate allocation to dynamic bit rate adjustment. The system calculates a quality measure for each frame and adjusts the quantization parameter dynamically based on the deviation from the mean quality measure of previous frames. This allows the bit rate to adapt to the specific characteristics of each frame while maintaining overall quality consistency.
Solution Approach 2:
The patent changes the quantization parameter dynamically based on the calculated quality measure and its deviation from the mean. By modifying the quantization parameter according to frame-specific quality characteristics, the system achieves both simplified control through a single parameter adjustment mechanism and improved picture quality through adaptive parameter changes.
2Manufacturing precision
If variable bit rate is allocated based on video signal characteristics, then picture quality improves, but bit rate control becomes more complex requiring quality measure calculation and comparison
Solution Approach 1:
The patent implements feedback by calculating the quality measure for each frame and comparing it to the mean quality measure of previous frames. The deviation from this mean is fed back to adjust the quantization parameter, creating a closed-loop control system that continuously adapts bit rate allocation to maintain optimal picture quality while managing complexity through systematic feedback processing.
3Manufacturing precision
If quantization parameter is reset when deviation exceeds critical value, then picture quality variation is minimized, but processing time increases due to additional comparison and adjustment operations
Solution Approach 1:
The patent applies partial action by implementing quantization parameter reset only when the deviation from the mean quality measure exceeds a predetermined critical value. This selective adjustment approach maintains picture quality consistency for frames that significantly deviate from the average while avoiding unnecessary processing for frames that fall within the acceptable range, thus balancing quality consistency with processing efficiency.
Data Source
AI summary
A bit rate control method may include calculating a quality measure of a current frame and a mean of quality measures of two or more previous frames in order to calculate a deviation of the quality measure of the current frame from the mean of the quality measures of the two or more previous frames; comparing the deviation to a critical value measure; and controlling a quantization parameter in response to a result of the comparison. A bit rate control apparatus may include a quality measure calculator that calculates the quality measure of the current frame and the mean of the quality measures of the two or more previous frames in order to calculate the deviation; a comparator that compares the deviation to the critical value measure; and a quantization parameter setting unit that controls the quantization parameter in response to the result of the comparison.