[Bug 17004] New: Define a timestamp offset mechanism

https://www.w3.org/Bugs/Public/show_bug.cgi?id=17004

           Summary: Define a timestamp offset mechanism
           Product: HTML WG
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Media Source Extensions
        AssignedTo: adrianba@microsoft.com
        ReportedBy: acolwell@chromium.org
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,
                    public-html@w3.org


The current spec text does not provide a mechanism to apply an offset to
timestamps in media segments. This feature is primarily for ad insertion and
mashups use cases. It would allow web applications to easily append content
into the middle of presentations without resorting to format parsing &
rewriting to adjust the timestamps.

Method signature suggestions:

void sourceTimestampMapping(in double presentationTimestamp, in double 
segmentTimestamp)

-- or --

void sourceTimestampOffset(in double timstampOffset)

The method would specify the timestamp mapping to use for future media segments
that get appended. If the UA is in the middle of parsing a media segment, it
must defer applying the new offset until the end of the current segment. The
mapping would be applied at append time before the data goes into the source
buffer. This allows the source buffer to solely deal with presentation
timestamps. 

This is just an initial outline for the feature. There are likely other
semantics that need to be nailed down as well.

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Received on Tuesday, 8 May 2012 21:07:38 UTC