Black Bar Detection for Perceptual Video Quality Improvement
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Solution Overview
Problem
Video sequences with black bars due to aspect ratio mismatches between video content and display devices suffer from poor perceptual quality due to issues like boundary artifacts, non-uniform encoding, and pulsating artifacts, especially when encoded with High Efficiency Video Codecs (HEVC) and at high or low bitrates.
Innovation Solution
The solution involves detecting black bars and modifying encoder operations by using 4 Mv/MB or 16 Mv/MB for partial black bars, forcing all full black bar macroblocks to be skip macroblocks, and disabling row-level rate control for full black bar rows to ensure uniform video quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard video encoding is used for videos with black bars, then encoding complexity is reduced, but perceptual video quality deteriorates due to boundary artifacts and non-uniform encoding
Solution Approach 1:
The patent applies preliminary action by detecting black bars before the encoding process and marking their locations. This pre-detection allows the encoder to apply specialized encoding modes (skip mode for full black bars, 4mv/mb or 16mv/mb for partial black bars) to the identified regions, preventing boundary artifacts and non-uniform encoding issues before they occur during standard encoding.
2Productivity
If row-level rate control is applied to videos with black bars, then bit rate distribution is optimized, but quality uniformity deteriorates due to non-uniform bit allocation across frames
Solution Approach 1:
The patent applies local quality by implementing differential rate control based on black bar detection. Full black bar rows are excluded from rate control calculations, while partial black bar regions use modified rate control parameters. This localized approach ensures that bit allocation is optimized for actual video content while preventing black bar regions from distorting the overall bit distribution, thereby maintaining quality uniformity across frames.
3Manufacturing precision
If high bitrate encoding is used for videos with black bars, then video quality is improved, but artifacts such as pulsating effects and boundary issues worsen
Solution Approach 1:
The patent converts the potentially harmful effect of high bitrate encoding on black bar regions into a benefit by detecting black bars and applying skip mode encoding to full black bar macroblocks. This prevents the generation of pulsating artifacts and boundary issues that would otherwise occur with standard high bitrate encoding, while still allowing high quality encoding for the actual video content regions.
Data Source
AI summary
A method of improving the perceptual video quality of video sequences containing black bars. Horizontal or vertical black bars caused by a missmatch between the aspect ratio of the encoded video and the display device. The presence of black bars is detected, and the encoding process is adjusted to eliminate visual depredation of the reproduced video.