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Review of MFWG use cases and requirements

From: Bailer, Werner <werner.bailer@joanneum.at>
Date: Thu, 3 Sep 2009 16:08:45 +0200
To: "public-media-annotation@w3.org" <public-media-annotation@w3.org>
Message-ID: <CD9846F872C7874BB4E0FDF2A61EF09F2E2294BE21@RZJC1EX.jr1.local>
Dear all,

As stated in Tuesday's telecon I reviewed the MFWG use cases and requirements WD. Please find below my comments (to be merged with those of other reviewers).

- 3.6 Singe fragment: Not sure that the term 'mask' is the best choice here, e.g. in MPEG-7 mask is used for the opposite, i.e. not a single segment but a segment composed of several unconnected parts.

- 4.4 Annotating media fragments: A reference to the MAWG deliverables could be added here.

- 6.2.1 temporal dimension: Currently on three frame rates are supported for frame-precise addressing. Especially given the fact that the HDTV standards include other frame rates (e.g. 24, 50, 60), which can be expected to be also increasingly available on the web, it seems useful to adopt a more generic support for frame-precise addressing (cf. the proposal to use edit units).

- 6.3.2 track dimension: The restriction to only a single track seems to be a problem for some of the intended use cases, e.g. scenario 5 in 4.5.5 mentions that Katrina would like to receive the original audio + the audio commentary for visually impaired. How would she request the two tracks? A similar problem is requesting the video stream + the French audio (but not the English and Spanish audio, and not the Dutch captions).

- editorial note in 6.2.3 on track names: MAWG discussed about the support of fragments in the MAWG API in the F2F in June. One result was to add a property ma:numTracks which then allow to iterate through the tracks numerically and query language, format, title (if supported) for each track fragment. This could be used to construct appropriate fragment identifiers. 

- 6.4 semantics, editorial note on reasonably close to requested segment: Returning something close to the requested fragment to avoid transcoding seems a good choice for use cases like display, browsing, etc. However, for the recompositing use cases a precise fragment might be preferred even if it requires transcoding. It might be an option to include in the request whether the fragment request is to be interpreted strictly or not. 

Best regards,
Werner

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  Werner Bailer
  Institute of Information Systems
  JOANNEUM RESEARCH Forschungsgesellschaft mbH
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Received on Thursday, 3 September 2009 14:10:51 GMT

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