Objective image quality metrics try to estimate the perceptual quality of the given image by considering the characteristics of the human visual system. However, it is possible that the metrics produce different quality scores even for two images that are perceptually indistinguishable by human viewers, which have not been considered in the existing studies related to objective quality assessment. In this paper, we address the issue of ambiguity of objective image quality assessment. We propose an approach to obtain an ambiguity interval of an objective metric, within which the quality score difference is not perceptually significant. In particular, we use the visual difference predictor, which can consider viewing conditions that are important for visual quality perception. In order to demonstrate the usefulness of the proposed approach, we conduct experiments with 33 state-of-the-art image quality metrics in the viewpoint of their accuracy and ambiguity for three image quality databases. The results show that the ambiguity intervals can be applied as an additional figure of merit when conventional performance measurement does not determine superiority between the metrics. The effect of the viewing distance on the ambiguity interval is also shown.

中文翻译：

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客观图像质量指标的歧义：一种新的性能评估方法

客观的图像质量度量试图通过考虑人类视觉系统的特征来估计给定图像的感知质量。但是，即使对于人类观看者在感觉上无法区分的两个图像，度量标准也可能会产生不同的质量得分，这在与客观质量评估相关的现有研究中并未考虑。在本文中，我们解决了客观图像质量评估的歧义性问题。我们提出一种方法来获取客观度量的歧义区间，在该区间中质量得分差异并不明显。特别是，我们使用视觉差异预测器，它可以考虑对于视觉质量感知非常重要的观看条件。为了证明提议的方法的有用性，考虑到三个图像质量数据库的准确性和歧义性，我们使用33个最先进的图像质量指标进行了实验。结果表明，当常规性能测量不能确定度量之间的优势时，歧义区间可以用作附加的品质因数。还显示了观看距离对歧义间隔的影响。