In this paper we explore the relation between subjective and objective measures of video quality. We computed objective
MOS values from video clips using the video quality measuring tool VQM and compared it to the clips' subjective
Acceptability scores. Using the ITU defined mapping (M2G) from MOS to binary Good or Better (GoB) values, we
compared the M2G translated values to the clips' subjective Acceptability scores at various encoding bitrates (32-224kbps) and sizes (120x90, 168x126, 208x156 and 240x180). The results show that in the domain of mobile TV the
ITU mapping M2G represents a serious overestimation of Acceptability.
The mapping M2A, between MOS and Acceptability, that we suggest provides a significant improvement of 76% in the
root mean square error (RMSE) over M2G. We show that Acceptability depended on more than just the visual quality
and that both content type and size are essential to provide accurate estimates of Acceptability in the field of mobile TV.
We illustrate this gain in Acceptability predictions for the popular content type football (soccer). In terms of RMSE our
content dependent mapping (M2Af) yielded an improvement of 39% over M2A. Future research will validate the
predictive power of our suggested mapping on other video material.
This paper presents the results from three lab-based studies that investigated different ways of delivering Mobile TV News by measuring user responses to different encoding bitrates, image resolutions and text quality. All studies were carried out with participants watching News content on mobile devices, with a total of 216 participants rating the acceptability of the viewing experience. Study 1 compared the acceptability of a 15-second video clip at different video and audio encoding bit rates on a 3G phone at a resolution of 176x144 and an iPAQ PDA (240x180). Study 2 measured the acceptability of video quality of full feature news clips of 2.5 minutes which were recorded from broadcast TV, encoded at resolutions ranging from 120x90 to 240x180, and combined with different encoding bit rates and audio qualities presented on an iPAQ. Study 3 improved the legibility of the text included in the video simulating a separate text delivery. The acceptability of News' video quality was greatly reduced at a resolution of 120x90. The legibility of text was a decisive factor in the participants' assessment of the video quality. Resolutions of 168x126 and higher were substantially more acceptable when they were accompanied by optimized high quality text compared to proportionally scaled inline text. When accompanied by high quality text TV news clips were acceptable to the vast majority of participants at resolutions as small as 168x126 for video encoding bitrates of 160kbps and higher. Service designers and operators can apply this knowledge to design a cost-effective mobile TV experience.
Conference Committee Involvement (6)
Multimedia on Mobile Devices 2013
4 February 2013 | Burlingame, California, United States
Multimedia on Mobile Devices 2012
25 January 2012 | Burlingame, California, United States
Multimedia on Mobile Devices 2011
25 January 2011 | San Francisco Airport, California, United States
Multimedia on Mobile Devices 2010
18 January 2010 | San Jose, California, United States
Multimedia on Mobile Devices 2009
19 January 2009 | San Jose, California, United States
Multimedia on Mobile Devices 2008
28 January 2008 | San Jose, California, United States