Adaptive Deblocking Filter Strength Control

Solution Overview

Problem

Existing deblocking filters in video codecs struggle to efficiently control filtering strength, leading to either ineffective removal of artifacts or excessive smoothing of original content, especially at low bit-rates and high resolutions, due to the lack of selective control over strong deblocking filtering.

Innovation Solution

A deblocking or deringing filter that varies its strength based on local measures of mean block size and frequency of non-zero prediction residuals, allowing for selective application of filtering strengths on a block-by-block basis, reducing the need for additional signaling bits and improving image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If strong deblocking filtering is applied to remove artifacts at low bit-rates, then artifact removal effectiveness is improved, but original image content may be smoothed out and erased

Engineering Contradiction:

Improveartifact removal effectivenessVSAvoidsmoothing of original content

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different filtering strengths to different regions of the image based on local characteristics. The deblocking filter strength is adjusted locally according to the presence of non-zero prediction residuals and block size, ensuring strong filtering only where artifacts are present while preserving original content in other regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The filtering strength is made dynamic and adaptive rather than fixed. The deblocking filter automatically adjusts its strength based on local image characteristics (non-zero prediction residuals and block size), transitioning between strong and weak filtering modes as needed to balance artifact removal and content preservation

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If a bit-flag is signaled for each sub-block to control strong deblocking filter application, then selective filtering control is improved, but coding bit-rate increases to unacceptable level

Engineering Contradiction:

Improveselective filtering controlVSAvoidcoding bit-rate

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent extracts and utilizes information already present in the coded data stream (non-zero prediction residuals and block size) to control filter strength, rather than adding new signaling bits. The existing coded data serves dual purposes: both for reconstruction and for controlling the deblocking filter behavior

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system uses its own internal state (presence of non-zero prediction residuals and block size information) to automatically regulate the filtering process. The coded data stream itself provides the control signals needed for adaptive filtering without requiring external or additional signaling

Inventive Principle:

Principle #25Self-service

3Reliability

If deblocking filter strength is increased for large transform blocks in H.266/WC, then artifact removal is improved, but risk of smoothing out original image content increases

Engineering Contradiction:

Improveartifact removalVSAvoidsmoothing of original content

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different filtering strengths to different regions of the image based on local characteristics. The deblocking filter strength is adjusted locally according to the presence of non-zero prediction residuals and block size, ensuring strong filtering only where artifacts are present while preserving original content in other regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The filtering strength is made dynamic and adaptive rather than fixed. The deblocking filter automatically adjusts its strength based on local image characteristics (non-zero prediction residuals and block size), transitioning between strong and weak filtering modes as needed to balance artifact removal and content preservation

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP3857880B1Deblocking or deringing filter and encoder, decoder and method for applying and varying a strength of a deblocking or deringing filter

Publication Date: 2024.10.23 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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AI summary

The invention concerns an encoder, a decoder and methods for applying and varying a strength of a deblocking or deringing filter (110, 120) for filtering a block (1000) of a picture (12), wherein the deblocking filter (110, 120) is configured to determine, for each of at least eight border portions (1011, 1012, 1013, 1014, 1021, 1022, 1023, 1024) of a border (1010) of the block (1000), a dissimilarity between an unfiltered content (1015) of the block (1000) and a surrounding picture content (1016) around the block (1000) along the respective border portion (1011, 1012, 1013, 1014, 1021, 1022, 1023, 1024), the eight border portions (1011, 1012, 1013, 1014, 1021, 1022, 1023, 1024) including four corner border portions (1021, 1022, 1023, 1024), each arranged at a corner of the block (1000), and four edge border portions (1011, 1012, 1013, 1014), each arranged at intermediary portions of the border (1010) between the corners of the block (1000). Furthermore, the deblocking filter is configured to parametrize a deblocking filtering of the block (1000) using the dissimilarities determined for the at least eight border portions (1011, 1012, 1013, 1014, 1021, 1022, 1023, 1024) in order to obtain a filtered content of the block (1000).