Abstract
Subjective quality assessment is an essential component of modern image and video processing for both the validation of objective metrics and the comparison of coding methods. However, the standard procedures used to collect data can be prohibitively time consuming. One way of increasing the efficiency of data collection is to reduce the duration of test sequences from a 10-s length currently used in most subjective video quality assessment (VQA) experiments. Here, we explore the impact of reducing sequence length upon perceptual accuracy when identifying compression artifacts. A group of four reference sequences, together with five levels of distortion, are used to compare the subjective ratings of viewers watching videos between 1.5 and 10 s long. We identify a smooth function indicating that accuracy increases linearly as the length of the sequences increases from 1.5 to 7 s. The accuracy of observers viewing 1.5-s sequences was significantly inferior to those viewing sequences of 5, 7, and 10 s. We argue that sequences between 5 and 10 s produce satisfactory levels of accuracy but the practical benefits of acquiring more data lead us to recommend the use of 5-s sequences for future VQA studies that use the double stimulus continuous quality scale methodology.
Highlights
A S VISUAL display devices continue to pervade more of our lives, the need to provide their screens with optimized content is becoming no less critical
The development of objective video quality metrics has accelerated in recent years, but despite the multitude of different algorithmic solutions available, few produce satisfactory correlations with ground truth data collected from human viewers [1]
For a comprehensive guide to statistical analysis of subjective testing data, the reader is referred to International Telecommunications Union (ITU)-T Study Group 12 [27]
Summary
A S VISUAL display devices continue to pervade more of our lives, the need to provide their screens with optimized content is becoming no less critical. Subjective video databases include a set of original reference videos together with a group of variably distorted versions of each. A smaller subset of these videos, are associated with a quality rating obtained by displaying the videos to human observers and recording their mean opinion scores (MOSs). Subjective video databases aim to provide researchers with a set of resources allowing them to assess the impact upon perception of variable spatial and temporal video quality. They are primarily used for the validation of objective quality metrics or the performance comparison of different video coding methods
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