Abstract
When comparing the performance of video coding approaches, evaluating different commercial video encoders, or measuring the perceived video quality in a wireless environment, Rate/distortion analysis is commonly used, where distortion is usually measured in terms of PSNR values. However, PSNR does not always capture the distortion perceived by a human being. As a consequence, significant efforts have focused on defining an objective video quality metric that is able to assess quality in the same way as a human does. We perform a study of some available objective quality assessment metrics in order to evaluate their behavior in two different scenarios. First, we deal with video sequences compressed by different encoders at different bitrates in order to properly measure the video quality degradation associated with the encoding system. In addition, we evaluate the behavior of the quality metrics when measuring video distortions produced by packet losses in mobile ad hoc network scenarios with variable degrees of network congestion and node mobility. Our purpose is to determine if the analyzed metrics can replace the PSNR while comparing, designing, and evaluating video codec proposals, and, in particular, under video delivery scenarios characterized by bursty and frequent packet losses, such as wireless multihop environments.
Highlights
In the past years, the development of novel video coding technologies has spurred the interest in developing digital video communications, where evaluation mechanisms to assess the video quality play a major role in the overall design of video communication systems.The most reliable way of assessing zthe quality of a video is subjective evaluation, because human beings are the ultimate receivers in most applications
The metrics were first trained with a set of images from two open source image and video databases with known mean opinion score (MOS) values
The metrics were tested with another set of images and videos taken from available databases
Summary
The development of novel video coding technologies has spurred the interest in developing digital video communications, where evaluation mechanisms to assess the video quality play a major role in the overall design of video communication systems. The task of choosing “the best QAM” is influenced by too many factors and sources of inaccuracy These sources of inaccuracy are, for example, the reliability of unbiased subjective reference data, the selection of video or image contents, the degree of the impairments and where they appear (in space and time), the procedure used to map between subjective and objective quality values, and even the use and interpretation of the correlation indicators. When using R/D, the distortion is usually measured in terms of PSNR (peak signal-to-noise ratio) values, where rates are often measured in terms of bpp (bits per pixel) for images or bps (bits per second) for video In this test environment, we work with the selected QAM as candidates to replace the PSNR as the distortion metric in the R/D comparisons.
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