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Estimating the impact of single and multiple freezes on video quality

Author: Kester, S. van · Xiao, T. · Kooij, R.E. · Brunnström, K. · Ahmed, O.K.
Type:article
Date:2011
Source:Human Vision and Electronic Imaging XVI, 24-27 January 2011, San Francisco, CA, USA
series:
Proceedings of SPIE - The International Society for Optical Engineering
Identifier: 429047
doi: doi:10.1117/12.873390
Article number: 78650O
Keywords: Informatics · Channel video freezing · MOS · QoE · Subjective testing · Video · Communication & Information · PNS - Performance of Networks & Services · TS - Technical Sciences

Abstract

This paper studies the impact of freezing of video on quality as experienced by users. Two types of freezes are investigated. First a freeze where the image pauses, so no frames were lost (frame halt). In the second type of freeze, the image freezes and skips that part of the video (frame drop). Measuring Mean Opinion Score (MOS) was done by subjective tests. Video sequences of 20 seconds were displayed for four types of content, to a total of 23 test subjects. We conclude there is no difference in the perceived quality between frame drops and frame halts. Therefore one model for single freezes was constructed. According to this model the acceptable freezing time (MOS>3.5) is 0.36 seconds. Pastrana - Vidal et al. (2004) suggested a relationship between the probability of detection and the duration of the dropped frames. They also found that it is important to consider not only the duration of the freeze but also the number of freeze occurrences. Using their relationship between the total duration of the freeze and the number of occurrences, we propose a model for multiple freezes, based upon our model for single freeze occurrences. A subjective test was designed to evaluate the performance of the model for multiple freezes. Good performance was found on this data i.e a correlation higher than 0.9.