EVALUATION OF SUBJECTIVE VIDEO QUALITY ON MOBILE DEVICES

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EVALUATION OF SUBJECTIVE VIDEO QUALITY ON MOBILE
DEVICES
Jukka Häkkinen _at_helsinki.fi, University of
Helsinki and Nokia Research
Satu Jumisko-Pyykkö _at_tut.fi, Tampere University
of Technology
ABSTRACT Subjectively perceived video quality is
a critical factor when adopting new mobile video
applications. When video is used in mobile
networks the most important requirements are
related to low bitrates, framerates and the
screen size of mobile device. In two tests we
investigated the effects of codecs and
combinations of audio and video streams with low
bitrates and different contents on the
perceived video quality of mobile devices. The
first test showed that the codec H.264 produced
the most satisfying video quality, but the
quality was not high enough for the
presentation of textual information. In the
second test, the audio-video ratio 32/128kbps was
found to be the most pleasant, but there were
content dependent variations.
THE VIDEO STUDY The most satisfying codec for
visual quality RESEARCH METHOD Participants 75
(18-65 years) stratified by age, gender, lt20
professionals Test procedure Single stimulus
method (ITU-R T.500-11) Contents Parameters
RESULTS H.264 the most satisfying
(plt0.001) In tele-text content, not
difference between the codecs
(pgt0.05) DISCUSSION AND CONCLUSIONS H.264
produces the most satisfying quality for
typical TV contents. The quality in details, e.g.
text quality is needed to be improved
for providing the satisfying quality.
Parameters
THE AUDIO-VIDEO STUDY The optimal audio-video
bitrate ratio RESEARCH METHOD Participants
60 (18-65 years) stratified by age, gender,
lt20 professionals Test procedure Single
stimulus method (ITU-R T.500-11) Pre-test
Sensory tests, demographic survey Test
Anchoring, training, actual test Post-test
Content survey, interview Contents Potential
for mobile TV, popular Spatial and temporal
resolution Parameters RESULTS The
highest quality score given for the ratio
32/128kbps DISCUSSION AND CONCLUSIONS Audio
and video ratios were strongly dependant on
contents. Content dependant requirements are
necessary to take into account for bandwidth
optimization to deliver acceptable quality in new
products such as mobile television.

Codecs H.263-AAC H.263-AAC H.263-AAC
Total bitrate (kbps) 160 160 160
Audio bitrate (kbps) 64 32 16
Video bitrate (kbps) 96 128 144
Framerate (fps) 12,5 12,5 12,5
Contents 5 5 5
Device Nokia 7700 Nokia 7700 Nokia 7700
Picture ratio QCIF QCIF QCIF
Codecs H.263 Real Video 8 H.264
Total bitrate (kbps) 80 80 80
Framerate (fps) 12,5 12,5 12,5
Contents 6 6 6
Device Nokia 6600 Nokia 6600 Nokia 6600
Picture ratio QCIF QCIF QCIF
Content Animation Ice hockey Music video News TV series
AV-ratio (kbps) 32/128 16/144 32/128, 64/96 64/96 32/128, 16/144