[Bug 21333] consequences of requirement in section 8 on initialisation segments

https://www.w3.org/Bugs/Public/show_bug.cgi?id=21333

--- Comment #10 from Michael Thornburgh <mthornbu@adobe.com> ---
(In reply to comment #8)> 
> Since MSE attempts to abstract away the network tier from HTML Media
> Elements, this suggestion seems equivalent to letting a data being
> progressively downloaded for a <source> element change format mid-download.
> I'm not aware of anyone building something like this. I don't think
> SourceBuffers should be required to support multiple formats.

if i gave a URL for a media file to a <video> element, and it was playable, the
least surprising thing to do would be to make a best effort to play it even if
the format changed partway through.  and note that some format changes are
allowed already (like video resolution or number of audio channels), but some
are not allowed (like codec, or number of tracks, or track IDs when there's
more than one track of a particular kind).

> If you have multiple SourceBuffers then you need to switch tracks, but you
> have this situation with HTML Media Elements already. It's not clear to me
> why the problem of track switching is specific to MSE. Isn't this actually a
> HTML5 issue that could be required of any media element including those
> performing progressive download over HTTP? As I suggested on the last call,
> this might be something solved outside the scope of MSE.

i agree that MSE isn't *necessarily* the place to solve the "seamless track
changes at exactly the right time" problem (although the existence of the
problem in the first place feels unnecessary to me).  however, seamless
playback is only part of the problem. i also enumerated issues from the
Javascript side, including SourceBuffer explosion and having to
manage/create/destroy multiple SourceBuffers in general, when all you want to
accomplish is to lay out some media in the timeline as naturally as possible
and have it play as smoothly as possible.

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Received on Tuesday, 26 March 2013 20:43:00 UTC