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Digital video quality vision models and metrics phần 8

Một số phần mở rộng của PDM được khám phá trong chương này. Đầu tiên là việc đánh giá các hiện vật chặn. PDM là kết hợp với một thuật toán để ngăn chặn phân khúc khu vực để dự đoán mức độ nhận thức ngăn chặn sự biến dạng. | 6 Metric Extensions The purpose of models is not to fit the data but to sharpen the questions. Samuel Karlin Several extensions of the PDM are explored in this chapter. The first is the evaluation of blocking artifacts. The PDM is combined with an algorithm for blocking region segmentation to predict the perceived degree of blocking distortion. The prediction performance of the resulting perceptual blocking distortion metric PBDM is analyzed using data from subjective experiments on blockiness. The second is the combination of the PDM with object segmentation. The necessary modifications of the metric are outlined and the performance of the segmentation-supported PDM is evaluated using sequences on which face segmentation was performed. Finally the addition of attributes specifically related to visual quality instead of just visual fidelity are investigated. Sharpness and colorfulness are identified among these attributes and are quantified through the previously defined isotropic local contrast measure and the distribution of chroma in the sequence respectively. The benefits of using these attributes are demonstrated with the help of additional test sequences and subjective experiments. 6.1 BLOCKING ARTIFACTS 6.1.1 Perceptual Blocking Distortion Metric Some applications require more specific quality indicators than an overall rating or a visual distortion map. For instance it can be useful to assess the Digital Video Quality - Vision Models and Metrics Stefan Winkler 2005 John Wiley Sons Ltd ISBN 0-470-02404-6 126 METRIC EXTENSIONS quality of certain image features such as contours textures blocking artifacts or motion rendition van den Branden Lambrecht 1996b . Such specific quality ratings can be helpful in testing and fine-tuning encoders for example. In particular compression artifacts see section 3.2.1 such as blockiness ringing or blur deserve a closer investigation. It is of interest to measure the perceived distortion caused by these different types of .