Video Encoder Rate Control via Sliding Window Complexity
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Solution Overview
Problem
Constant-bit-rate finite-buffer-size video encoders face challenges in maintaining visual quality due to buffer overflow and underflow conditions, requiring accurate prediction of future frame compression properties, which increases computational and storage demands, and is not economically viable.
Innovation Solution
The method adjusts non-intra frame sizes based on expected intra frame sizes using a sliding window approach and 'power' measurements, calculating global complexity to provide robust rate control without iterative encoding, utilizing past frame compression properties rather than future ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If accurate prediction of future frame compression properties is performed, then visual quality is improved, but computational and storage demands increase
Solution Approach 1:
The patent performs preliminary analysis of past frame compression properties to predict future frame characteristics. By analyzing historical compression data and frame characteristics in advance, the system prepares rate control parameters before encoding future frames, thereby improving visual quality without requiring excessive computational resources during actual encoding.
Solution Approach 2:
The patent uses lightweight statistical models and simple frame characteristic analyses instead of complex prediction algorithms. By employing computationally inexpensive methods to estimate future frame properties based on past data, the system achieves acceptable prediction accuracy while minimizing computational and storage overhead.
2Measurement precision
If analysis of future frames is performed in advance, then rate control accuracy is improved, but system delay increases
Solution Approach 1:
The patent performs preliminary analysis of past frame compression properties to establish prediction models that can be quickly applied to future frames. By preparing statistical parameters and frame characteristic data in advance, the system achieves accurate rate control without requiring time-consuming analysis of actual future frames before encoding.
Solution Approach 2:
The system uses its own historical encoding data and frame characteristics to self-generate prediction information for future frames. By leveraging internally available data about past compression properties and frame types, the system avoids external delays while maintaining rate control accuracy.
3Measurement precision
If iterative encoding at different quantization step sizes is performed, then bit allocation accuracy is improved, but computational expense increases
Solution Approach 1:
The patent performs preliminary estimation of the relationship between quantization step size and bit count using past frame data. By establishing this relationship in advance through analysis of historical encoding statistics, the system can directly calculate appropriate quantization parameters without requiring multiple iterative encoding passes, thereby achieving accurate bit allocation with reduced computational expense.
4Reliability
If constant bit rate encoding is enforced, then buffer overflow and underflow are prevented, but visual quality varies
Solution Approach 1:
The patent dynamically adjusts rate control parameters based on predicted future frame characteristics and current buffer status. By making the bit allocation adaptive to predicted frame complexity and actual encoding conditions, the system maintains constant bit rate compliance while minimizing visual quality variations through intelligent parameter adjustment.
Solution Approach 2:
The system uses feedback from actual frame encoding results and buffer status to refine rate control decisions for subsequent frames. By continuously monitoring encoding outcomes and adjusting predictions accordingly, the system maintains buffer stability while adapting to actual visual content requirements, thereby reducing quality variations.
Data Source
AI summary
A method and apparatus for rate control for a constant-bit-rate finite-buffer-size video encoder is described. Rate control is provided by adjusting the size of non-intra frames based on the size of intra frames. A sliding window approach is implemented to avoid excessive adjustment of non-intra frames located near the end of a group of pictures. A measurement of “power” based on a sum of absolute values of pixel values is used. The “power” measurement is used to adjust a global complexity value, which is used to adjust the sizes of frames. The global complexity value responds to scene changes. An embodiment of the invention calculates and uses L1 distances and pixel block complexities to provide rate control. An embodiment of the invention implements a number of bit predictor block. Predictions may be performed at a group-of-pictures level, at a picture level, and at a pixel block level. An embodiment of the invention resets a global complexity parameter when a scene change occurs.