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Bug 25998 - Move timestamp less than "presentation start time" checks after "append window" filtering
Summary: Move timestamp less than "presentation start time" checks after "append windo...
Status: RESOLVED FIXED
Alias: None
Product: HTML WG
Classification: Unclassified
Component: Media Source Extensions (show other bugs)
Version: unspecified
Hardware: PC All
: P2 normal
Target Milestone: CR
Assignee: Aaron Colwell
QA Contact: HTML WG Bugzilla archive list
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Reported: 2014-06-06 01:45 UTC by Aaron Colwell
Modified: 2014-06-13 20:12 UTC (History)
2 users (show)

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Description Aaron Colwell 2014-06-06 01:45:35 UTC
Step 7 of the coded frame processing algorithm should be moved after steps 8-10 so that it is possible to append the middle of a media segment at the beginning of presentation.

Say I have a media segment that spans the range [0, 10) and has a random access point at time 5. To insert the range [5-10) at time 0, I would need to set timestampOffset to -5 before appending. The current location of the check would cause a "decode" error because the coded frame for presentation time 0 would become -5. If the check is moved after the append window, the coded frames with negative timestamps are automatically filtered out and the "decode" error is avoided.

As I side note, I realized that the constraints for setting appendWindowStart actually enforces "presentation timestamp > 0" so I can technically drop the presentation timestamp part of the check in Step 7.
Comment 1 Aaron Colwell 2014-06-13 20:12:43 UTC
Change committed.
https://dvcs.w3.org/hg/html-media/rev/cb96bc1c87c3

Moved step after append window filtering steps and removed presentation timestamp from the step because that case is covered by the append window filtering steps.