[Bug 21375] Decoding dependencies

https://www.w3.org/Bugs/Public/show_bug.cgi?id=21375

Aaron Colwell <acolwell@chromium.org> changed:

           What    |Removed                     |Added
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                 CC|                            |acolwell@chromium.org

--- Comment #1 from Aaron Colwell <acolwell@chromium.org> ---
(In reply to comment #0)
> The spec currently requires in the coded frame processing algorithm that
> implementation detect dependencies between frames so that removal of a frame
> removes all dependent frames. 
> 
> This is a strong requirement on implementations which is impossible to
> fulfill (at least with current media formats) without decoding the frames
> (codec specific parsing). 

This is not entirely true. We are doing this in Chrome right now. While it is
true that the exact dependencies require parsing the coded frame, deleting
everything between the current frame and the last random access point achieves
this goal w/o codec specific knowledge. One can simply use the keyframe
indicators and differences between dts & pts in the bytestream to approximate
the dependencies. More consistant terminology could probably be used in the
various places that coded frames are removed, but supporting this is not
impossible.

> 
> The requirement should be removed. Applications should make sure that they
> append frames that don't depend on non appended frames or that overlapped
> frames are not needed by non-overlapped frames.
I disagree. The application doesn't likely have such intimate details of the
encoding especially since it may not have actually created all the content it
wants to insert into the presentation.

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Received on Friday, 22 March 2013 17:46:24 UTC