SPIE06 breaking the news on mobile TV

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Breaking the News on Mobile TV: User requirements of a popular mobile content Hendrik Knoche*, Angela Sasse University College London

Motivation: 

Motivation Repurpose standard TV news “as is” How do different encoding bitrates of both audio and video affect the perceived video quality on mobile devices? Down to what resolutions? How big is the influence of text?

Previous research: 

Previous research Based on viewing ratio e.g. (5H) Size: The bigger the better (up to life size) Larger picture -> more arousal Smaller picture -> ? Conflicting information: 2” vs 13” screen no difference in attention benefits from smaller picture in lie detection (Horn ‘02) Emotion detection at full body view less accurate at smaller size 256x256 vs. 128x128

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Study 1 (N=20), 15 sec.

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Study 1: Summary Encoding bitrate of at least 100kbps Resolution and size have little effect Limitations: Small sample, few votes across codecs/devices short clip legible text

Study 2: Interface: 

Study 2: Interface

Study 2 (N=72) 4 clips, 2 audio: 

Study 2 (N=72) 4 clips, 2 audio

Study 2: Qualitative feedback: 

Study 2: Qualitative feedback

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Study 2: Summary Reducing image resolution biggest effect at enc. bitrates >100kbps Text legibility is biggest problem of recoded TV news content Better audio resulted in poorer video acceptability Limitations: employed text too small to be legible did not test participants visual acuity

Study 3: Preparation: 

Study 3: Preparation

Study 3: Preparation: 

Study 3: Preparation

Reminder Study 2: 

Reminder Study 2

Study 3: (N=20): 

Study 3: (N=20)

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Study 3: Summary tremendous gains through separate text delivery With legible text: acceptability for all resolutions reached asymptote ≥160kbps 168x126 was feasible for recoded TV News on a mobile device.

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Summary video (res, bitrate), text, and audio affect perceived video quality assure text legibility by re-layout or separate delivery - acceptability reached asymptote ≥160kbps for all resolutions 168x126 – 320x240 facial details are important Limitations: Assumption: perfect delivery

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Thank you! Breaking the News on Mobile TV: User requirements of a popular mobile content Hendrik Knoche*, Angela Sasse University College London h.knoche@cs.ucl.ac.uk Q&A