Adaptive Rate Control for Variable Frame Rate Video Encoding
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Solution Overview
Problem
Mobile devices face challenges in processing video data with variable frame rates due to limited resources and existing rate control algorithms that struggle with accurate frame rate estimation and resulting in noticeable delays or jerky motion in encoded video.
Innovation Solution
A method involving a rate control mechanism that adjusts a quantizer parameter based on a virtual buffer fill level calculated from the time difference and bit budget, allowing for efficient encoding of video frames at varying frame rates, including storing and averaging quantizer parameter values to restrict excessive changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing rate control algorithms are used with variable frame rate video data, then the encoding process can be performed, but noticeable delays and jerky motion occur in the encoded video
Solution Approach 1:
The patent implements a dynamic rate control mechanism that adapts the quantizer parameter in real-time based on the actual frame rate of incoming video data. The system continuously monitors the frame rate and adjusts encoding parameters dynamically, allowing the encoder to handle variable frame rates gracefully without producing noticeable delays or jerky motion, thus resolving the contradiction between encoding efficiency and video quality.
Solution Approach 2:
The patent employs a feedback mechanism where the actual frame rate of the incoming video data is fed back into the rate control algorithm. This feedback loop allows the system to detect deviations from the expected frame rate and adjust the quantizer parameter accordingly, ensuring smooth encoding transitions and maintaining video quality while handling variable frame rates effectively.
2Adaptability or versatility
If frame rate estimation is performed on instantaneous video capture data, then adaptation to variable frame rates is attempted, but accurate estimation becomes very difficult or impossible
Solution Approach 1:
The patent applies preliminary action by using a smoothed frame rate estimate that is updated progressively over time rather than attempting to estimate the frame rate instantaneously. The system maintains a running average or exponential moving average of the frame rate, which provides a stable and accurate estimate even when the actual frame rate is highly variable, thus resolving the contradiction between adaptability and measurement precision.
3Ease of operation
If video frames are re-sampled at fixed time instants to model a fixed frame rate source, then rate control can be applied, but noticeable delays and jerky motion occur
Solution Approach 1:
The patent replaces the static fixed frame rate assumption with a dynamic frame rate model that adapts to the actual variable frame rate of the incoming video data. The rate control algorithm continuously adjusts the quantizer parameter based on the actual frame rate, eliminating the need for artificial re-sampling and preserving the natural timing characteristics of the video stream, thus resolving the contradiction between ease of operation and motion smoothness.
Data Source
AI summary
Techniques for performing rate control for encoding of video frames are provided. A first timestamp that indicates a prior video frame capture time and a second timestamp that indicates a current video frame capture time are received. A time difference between these timestamps is determined. An average video data bit encoding rate is multiplied by the determined time difference to calculate a bit budget. An indication of a number of encoded video data bits of the prior video frame and of any further video frames encoded subsequent to the prior video frame and prior to the current video frame is received. A virtual buffer fill level is adjusted based on a difference between the indicated number of encoded video bits and the calculated bit budget. A quantizer parameter is adjusted based on the adjusted virtual buffer fill level. The current video frame is encoded according to the adjusted quantizer parameter.