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[Bug 18602] New: Unclear requirements for WebM byte streams

From: <bugzilla@jessica.w3.org>
Date: Fri, 17 Aug 2012 13:31:15 +0000
To: public-html-media@w3.org
Message-ID: <bug-18602-5436@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=18602

           Summary: Unclear requirements for WebM byte streams
           Product: HTML WG
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Media Source Extensions
        AssignedTo: adrianba@microsoft.com
        ReportedBy: philipj@opera.com
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-media@w3.org


http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#webm

(One bug for a number of minor issues.)

"Exactly one Segment Information element must appear after the Segment header."
"Exactly one Tracks element must appear after the Segment Information element."

It's not clear if this is intended to mean "directly after" or not. Presumably
it's OK to have other elements in between.

"Meta Seek Information, Cues, Chapters, and various Global Elements may follow
the Segment header but the contents of these elements will be ignored.
Note: This enables the use case where the contents of a WebM file are simply
appended without any inspection or reformatting."

"various Global Elements" isn't very clear. Presumable any unknown element
should be ignored? "will be ignored" should be "should be ignored" or "must be
ignored" to be normative.

"If the most recent WebM initialization segment describes multiple tracks, then
blocks from all the tracks must be present and interleaved in time increasing
order."

This could be read as requiring that blocks for all tracks be included in all
segments, which may not be intentional. For text tracks there may simply be no
data for a particular segment, and for sufficiently small segments suboptimal
muxing could cause the requirement to fail.

Finally, for all of these requirements it must be defined what should happen if
they are violated, presumably causing a decoding error.

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Received on Friday, 17 August 2012 13:31:40 UTC

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