Video Encoder Latency Reduction via Dynamic Quantization
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Solution Overview
Problem
Existing video encoding technologies face challenges in reducing latency while maintaining acceptable video quality, particularly in applications requiring low latency video transmission over long distances, such as visual aids for vehicle drivers.
Innovation Solution
A method and device that adapt the quantization parameter (QP) in real-time to limit frame sizes, using a rate control mechanism to ensure frame sizes do not exceed processing capabilities on the receive side, thereby reducing latency by dynamically adjusting the compression rate during video encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If video encoding is performed with high compression to reduce transmission time, then latency is reduced, but video quality deteriorates
Solution Approach 1:
The patent implements dynamic rate control that continuously adapts the quantization parameter based on real-time buffer status and scene complexity. The rate control mechanism dynamically adjusts compression strength between frames, using lower compression (higher QP) when the buffer is near capacity to prevent overflow, and higher compression (lower QP) when buffer space is available, thereby reducing latency while maintaining video quality within acceptable bounds
Solution Approach 2:
The patent changes the quantization parameter (QP) dynamically during encoding based on buffer occupancy and scene characteristics. By adjusting QP values in real-time rather than using a fixed compression rate, the system can control the balance between latency reduction and video quality preservation, allowing flexible adaptation to different transmission conditions and buffer states
2Loss of time
If frame size is reduced to speed up transmission, then latency is reduced, but video quality deteriorates
Solution Approach 1:
The patent performs preliminary estimation of the current frame size before actual encoding based on previous frame characteristics and scene complexity. This allows the rate control mechanism to pre-adjust the quantization parameter to achieve the target frame size, preventing buffer overflow while maintaining optimal video quality. The preliminary sizing action enables proactive latency reduction without sacrificing quality
Solution Approach 2:
The patent implements a feedback loop where the actual frame size is measured after encoding and compared against the target frame size. Based on this feedback, the quantization parameter is adjusted for subsequent frames to maintain the desired frame size. This closed-loop control ensures that transmission time is optimized while video quality remains within acceptable parameters
3Speed
If quantization parameter is increased to reduce frame size, then transmission speed increases, but video quality deteriorates
Solution Approach 1:
The patent dynamically adjusts the quantization parameter based on real-time buffer status and scene complexity rather than using a fixed high QP value. When buffer occupancy is low and scenes are simple, lower QP values are used to maintain video quality. When buffer occupancy is high or scenes are complex, higher QP values are used to reduce frame size and increase transmission speed, thereby dynamically optimizing the trade-off between speed and quality
Data Source
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AI summary
The invention concerns a method comprising: encoding, by a video encoder (102) and based on a first quantization factor (QP), one or more first groups of image blocks of a video frame; estimating, by a processing device, the size of an image slice comprising a plurality of further groups of image blocks to be encoded; and determining, based on the estimated size of the image slice, a second quantization factor (QP) to be applied to one or more of the further groups.