Sub-picture Rate Control for Video Encoding
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Solution Overview
Problem
Existing video encoding technologies face challenges in maintaining real-time encoding due to large encoded picture sizes, which lead to increased processing overhead and potential picture dropping, especially when constrained by maximum transmission unit (MTU) sizes in IP networks, resulting in degraded video quality.
Innovation Solution
Implementing sub-picture based rate control to determine the current encoded size of a picture and adjust the quantization scale for remaining macroblocks to ensure the encoded picture size does not exceed a maximum limit, thereby controlling the number of slices and reducing encoding time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the encoded picture size is increased to improve video quality, then the transmission time and buffering delay increase, but real-time interaction performance deteriorates
Solution Approach 1:
The rate control mechanism performs preliminary actions by monitoring the encoded picture size during the encoding process and adjusting quantization parameters in advance before the picture exceeds the maximum size limit. This prevents the picture size from becoming too large, thereby avoiding excessive transmission time and buffering delay while maintaining acceptable video quality.
2Manufacturing precision
If the encoded picture size is increased to improve video quality, then more bits are used, but the number of picture drops increases to meet real-time encoding requirements
Solution Approach 1:
The rate control mechanism implements feedback by continuously monitoring the encoded picture size and comparing it against the maximum size constraint. Based on this feedback, the system dynamically adjusts quantization parameters to ensure the picture size remains within acceptable limits, preventing picture drops while maintaining optimal video quality.
3Loss of time
If the maximum encoded picture size is constrained to reduce transmission delay, then the encoding complexity increases due to additional rate control computations
Solution Approach 1:
The rate control mechanism applies partial action by adjusting quantization parameters only for the remaining macroblocks when the current encoded picture size approaches the maximum limit. Instead of re-encoding the entire picture, the system performs rate control on the remaining portions, reducing the computational overhead while still ensuring the final picture size constraint is met.
4Adaptability or versatility
If slice-based encoding is used to comply with MTU constraints, then the number of slices increases, but the encoding time increases due to additional slice header overhead
Solution Approach 1:
The rate control mechanism changes parameters by dynamically adjusting the maximum picture size constraint based on the target bit rate and current encoding progress. By optimizing the quantization parameters and controlling the picture size, the system reduces the number of slices required to comply with MTU constraints, thereby reducing slice header overhead and improving encoding speed while maintaining network compatibility.
Data Source
AI summary
A method for encoding a picture in a video sequence is provided that includes determining the current encoded size of the picture after coding a plurality of macroblocks in the picture, determining that encoding remaining macroblocks in the picture may cause the encoded size of the picture to exceed a maximum encoded picture size, computing a quantization scale responsive to the determining, wherein the quantization scale is computed such that the estimated encoded size of the remaining macroblocks if the remaining macroblocks are quantized with the quantization scale does not exceed the difference between the maximum encoded picture size and the current encoded picture size, and quantizing at least one of the remaining macroblocks with the new quantization scale.