[Bug 26925] New: [InbandTracks] DASH Text Track Mapping

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26925

            Bug ID: 26925
           Summary: [InbandTracks] DASH Text Track Mapping
           Product: HTML WG
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Sourcing In-band Media Resource Tracks
          Assignee: silviapfeiffer1@gmail.com
          Reporter: cyril.concolato@telecom-paristech.fr
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-admin@w3.org

The current text in "5. Mapping text track content into text track cues" is
completely ununderstandable. 

What does the following sentence mean?
"DASH text track data may be contained in files or encapsulated in MPEG media
container formats ISOBMFF and MPEG-2 TS."
There is no such thing as a "DASH text track". What does it mean that "data may
be contained in files"? What files are we talking about here: MPD? What data
are we talking about: media data?
What is the purpose of the first paragraph ? It has no normative statement.
What should UA or applications do with it?
Suggestion: remove that paragraph.

That other sentence does not make sense:
"DASH text track data is in a file in the WebVTT format if the file MIME type
is "text/vtt" and should be exposed as a VTTCue as defined in [WEBVTT]"
The first part is a tautology: data in a file is of WebVTT format if the MIME
is text/vtt. That's by definition of WebVTT. Does the sentence use the "if" in
the wrong place ? Do you want to say the following:
"If a DASH MPD references content identified by the MIME type "text/vtt", that
content shall be exposed as a TextTrack using VTTCue as defined in [WEBVTT]" 
The same is true for the next sentence for TTML.

Why are those statements about WebVTT or TTML in the DASH section anyway? It
should be applicable to any container/manifest format (e.g HLS, ...). 
Suggestion: Remove WebVTT and TTML specific content from the DASH section and
create separate sections.

The sentence about MP4 has the same problem plus others:
" "application/mp4" (ISOBMFF container with one track) " is wrong. MP4 files
advertised with a MIME "application/mp4" may have multiple tracks. RFC 4337
indicates (in guidelines not in normative statement) that it should not contain
audio or visual material. It may contain multiple MPEG-7 tracks or else.
Suggestion: Rephrase saying:
"If content is identified by a MIME type used in section ISOBMFF, the mapping
in that section applies".

Same problem with the sentence about MPEG-2 TS. Same suggestion.

I can make all those changes in a pull request if you want.

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Received on Monday, 29 September 2014 10:11:57 UTC