HEVC Strong Filter Threshold Adaptation for Block Noise
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Solution Overview
Problem
In the HEVC draft, the weak filter is often applied in areas with significant block noise, leading to residual block noise issues.
Innovation Solution
An image processing device that determines whether to apply a strong filter using a strength parameter and a determination parameter, with the filter determination unit deciding based on a value obtained by multiplying these parameters, and adjusting the threshold for the strong filter application to increase its application in noisy areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the weak filter is applied in areas with significant block noise, then the filter is conservative and preserves more original image details, but the block noise remains visible and image quality deteriorates
Solution Approach 1:
The patent changes the determination parameter (threshold value) for filter application based on the prediction mode. For intra prediction modes, a lower threshold is used to apply the strong filter more aggressively, while for inter prediction modes, a higher threshold is used. This parameter adaptation allows the system to suppress block noise effectively in areas where it occurs (intra prediction) while avoiding over-filtering in areas where it doesn't occur (inter prediction).
Solution Approach 2:
The patent applies different filter strength criteria to different regions of the image based on their prediction mode characteristics. By identifying whether a block boundary is between intra-predicted blocks or inter-predicted blocks, the system locally adapts the filter application strategy, applying strong filter more aggressively in intra prediction regions where block noise is more likely to occur.
2Object-generated harmful factors
If the strong filter is applied more aggressively to suppress block noise, then block noise is reduced, but image artifacts and loss of detail may increase
Solution Approach 1:
The patent dynamically adjusts the filter determination threshold based on prediction mode parameters. By using a lower threshold for intra prediction modes and a higher threshold for inter prediction modes, the system applies the strong filter more aggressively only where block noise is likely to occur, while avoiding excessive filtering in other regions, thus balancing noise suppression with artifact prevention.
Solution Approach 2:
The filter determination is made dynamic by adjusting the threshold parameter according to the prediction mode of each block boundary. This dynamic adaptation allows the system to respond to different image characteristics and prediction scenarios, applying strong filter strength only when and where it is most needed, rather than using a fixed aggressive filtering approach throughout the entire image.
Data Source
AI summary
The present invention relates to image processing device and method which can suppress block noise. A filter strength determination unit determines the filter strength for every four lines under the control of a control unit. In other words, if a block boundary determination unit has determined to perform filtering, the filter strength determination unit determines at which strength of the strong filter or the weak filter the filtering process is performed, and outputs the determination result to a filter calculation unit. On this occasion, the filter strength determination unit uses the Bs value in the determination formula of the strong filter. For example, in the case of using the Bs value, the threshold of the determination is set in accordance with a linear function of the Bs value from the control unit. The present disclosure can be applied to, for example, an image processing device.