H.264/AVC coding performance enhancement via incorporating pre-process with perceptual-based in-loop deblocking filters
Date Issued
2005
Date
2005
Author(s)
Wang, Sheng-Ho
DOI
en-US
Abstract
Block-based video coding cooperating with block transform and block motion compensation is the most widely adopted way to reduce the data redundancy in various video coding standards. Although the goal of de-correlations is achieved effectively by this way, the most annoying artifact known as the blocking effect also comes into existence. To both remove this artifact and improve the coding performance simultaneously, the latest video coding standard, H.264/AVC, enforces the deblocking filters inside its coding loop.
In the design of deblocking filters of H.264/AVC, one pair of parameters, OffsetA and OffsetB, are provided, which allow the adaptive control of the deblocking strength in slice level. Thus, finding out better parameters for conducting the deblocking process of H.264/AVC is capable of improving visual quality of reconstructed video. Identifying which edges belong to blocking effect relies on perceptual judgment of human beings. In fact, this subjective assessment may not exactly match existing objective measurements and high PSNR does not always stand for less blocking artifacts. In this thesis, we introduce two new criteria for measuring the blocking distortion by analyzing the perceptual difference between the source and the reconstruction. The experimental results validate the proposed approaches, especially in subjective issues. On the other hand, another implicit advantage of deblocking is ignored by most encoders. It is observed that different coded images may have the same output after applying the mandatory deblocking process. Based on this observation, we integrate this concept into H.264/AVC. For eight different deblocking modes, we first derive the equations to change the input image but do not affect the final output reconstruction. By choosing those of less bitrate consumption, the proposed pre-processing approach successfully improves video coding performance.
Combing advantages of both pre-process and post-process, an enhanced H.264/AVC coding system is implemented which maximizes the effect of deblocking filters. The experimental results demonstrate its improvements for H.264/AVC codec both in objective and subjective evaluations
Subjects
資料壓縮
去方塊效應濾波器
後處理機制
前處理機制
H.264
Deblocking filter
Post-processing
Pre-processing
Type
thesis
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