Adaptive De-blocking Filter for MPEG Video Decoding
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Solution Overview
Problem
Existing methods for reducing blocking artifacts in MPEG-coded video are either too complex for real-time applications or ineffective at medium to high bit rates, limiting their suitability for modern video standards like digital versatile discs and digital TV.
Innovation Solution
A highly adaptive de-blocking filter that determines a filtering range and region mode based on local activity and quantization parameters, using symmetric or asymmetric filters to refine pixel values around block boundaries, effectively reducing blocking artifacts across a wide range of bit rates with low computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional de-blocking filters are used to reduce blocking artifacts, then blocking artifacts are reduced, but computational complexity increases making real-time operation difficult
Solution Approach 1:
The patent applies different filtering strengths (strong, medium, weak) to different block boundaries based on local characteristics such as quantization parameter values and block types. This selective filtering approach reduces computational complexity by avoiding uniform strong filtering across all boundaries while still effectively reducing visible blocking artifacts in critical areas.
Solution Approach 2:
The patent dynamically adjusts filtering parameters including filtering range, filtering strength, and threshold values based on local activity measurements and quantization parameters. This adaptive approach optimizes the balance between artifact reduction and computational efficiency by applying stronger filtering only where necessary rather than uniformly across the entire image.
2Object-affected harmful factors
If strong filtering is applied to reduce blocking artifacts, then artifact reduction improves, but image sharpness and detail are lost
Solution Approach 1:
The patent selectively applies strong filtering only to block boundaries with low local activity (smooth regions), while applying weak or no filtering to boundaries with high local activity (edges and detailed regions). This preserves image sharpness in critical areas while still reducing blocking artifacts in smooth regions where they are most visible.
Solution Approach 2:
The filtering strength is dynamically adjusted based on local activity measurements and quantization parameters. The patent uses activity thresholds to determine whether to apply strong, medium, or weak filtering, and dynamically sets filtering ranges based on quantization parameter values, thereby adapting the filtering intensity to local image characteristics to preserve sharpness where needed.
3Adaptability or versatility
If adaptive filtering with multiple parameters is used to improve quality across different bit rates, then quality improves, but device complexity and computational overhead increase
Solution Approach 1:
The patent changes key filtering parameters (filtering range, filtering strength, thresholds) based on quantization parameter values and block types. Specifically, the filtering range is set to 1 or 2 pixels based on QP thresholds, filtering strength is selected from strong/medium/weak based on local activity and QP, and activity thresholds are adjusted based on QP values. This parameter adaptation enables effective filtering across different bit rates without requiring a completely different filtering strategy for each case.
Solution Approach 2:
The patent segments the filtering process into distinct stages: block boundary identification, local activity measurement, filtering type selection, and actual filtering application. It also segments different block types (intra-coded, inter-coded, skip blocks) and applies appropriate filtering strategies to each segment, thereby managing complexity through structured organization of the adaptive filtering process.
Data Source
AI summary
A post processing de-blocking filter includes a threshold determination unit for adaptively determining a plurality of threshold values according to at least differences in quantization parameters QPs of a plurality of adjacent blocks in a received video stream and to a user defined offset (UDO) allowing the threshold levels to be adjusted according to the UDO value; an interpolation unit for performing an interpolation operation to estimate pixel values in an interlaced field if the video stream comprises interlaced video; and a de-blocking filtering unit for determining a filtering range specifying a maximum number of pixels to filter around a block boundary between the adjacent blocks, determining a region mode according to local activity around the block boundary, selecting one of a plurality of at least three filters, and filtering a plurality of pixels around the block boundary according to the filtering range, the region mode, and the selected filter.