Video Encoder Temporal Noise Filtering for Bitrate Reduction
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Solution Overview
Problem
Video encoding systems face challenges in reducing bitrate while maintaining image quality, particularly due to temporal noise fluctuations in static regions of video streams, which increase encoding costs for inter-coded blocks.
Innovation Solution
A method where pixel values in static regions of a video frame are 'frozen' at the temporally filtered value during inter-coding, updating only when the block is intra-coded, and using the temporally filtered value for encoding in static regions, thereby reducing bitrate without compromising image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If temporal noise filtering is applied before encoding, then noise is reduced without introducing artefacts, but temporal fluctuations in pixel values still increase the output bitrate
Solution Approach 1:
The patent applies preliminary temporal noise filtering before the encoding process to reduce noise in static regions. This preprocessing step removes temporal fluctuations in pixel values before encoding, thereby reducing the bitrate required to encode the video stream without compromising image quality.
Solution Approach 2:
The patent applies different encoding strategies to different regions of the video frame. Static regions undergo temporal noise filtering and are encoded with reference to previous frames, while moving regions are encoded independently. This local differentiation reduces overall bitrate by exploiting the temporal redundancy present in static regions.
2Quantity of substance
If pixel values are frozen at temporally filtered values for inter-coded blocks, then bitrate is reduced, but image quality may be compromised without updates
Solution Approach 1:
The patent periodically updates the frozen pixel values by incorporating new temporally filtered values at regular intervals or when certain conditions are met. This periodic update mechanism ensures that the frozen values remain accurate representations of the static regions over time, maintaining image quality while still achieving bitrate reduction through the freezing approach.
Solution Approach 2:
The patent uses feedback from the encoding process to determine when and how to update frozen pixel values. By monitoring encoding results and temporal changes, the system intelligently updates frozen values only when necessary, balancing bitrate reduction with image quality preservation through adaptive feedback control.
Data Source
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AI summary
There is provided a method of encoding a video stream. The method comprises receiving a frame of a video stream to be encoded, performing motion detection in the frame to identify steady regions, and temporally filtering the frame so as to provide temporally filtered pixel values. For a pixel in the steady regions of the frame, the temporally filtered pixel value is used when encoding the pixel, on a condition that the pixel belongs to a block of pixels of the frame that will be intra-coded. On a condition that the pixel instead belongs to a block of pixels of the frame that will be inter-coded, a value that was used when encoding a corresponding pixel of the immediately preceding frame is used when encoding the pixel.