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Re: Clarification of addSourceBuffer() method

From: Cyril Concolato <cyril.concolato@telecom-paristech.fr>
Date: Mon, 20 Oct 2014 09:48:23 +0200
Message-ID: <5444BE47.5040106@telecom-paristech.fr>
To: public-html-media@w3.org
Le 20/10/2014 03:27, Silvia Pfeiffer a écrit :
> I'm just taking a look at the MSE spec (writing a book chapter about
> it, actually).
> I'm looking at MediaSource.addSourceBuffer() which to me seems to be
> the key method to add chunks of a media resource to a MediaSource
> object.
> I'm reading the following in the spec:
> ``
> addSourceBuffer
> Adds a new SourceBuffer to sourceBuffers.
> Implementations must support at least 1 MediaSource object with the
> following SourceBuffer configurations. MediaSource objects must
> support each of the configurations below, but they are only required
> to support one configuration at a time. Supporting multiple
> configurations at once or additional configurations is a quality of
> implementation issue.
> * A single SourceBuffer with 1 audio track and/or 1 video track.
> * Two SourceBuffers with one handling a single audio track and the
> other handling a single video track.
> ``
> It seems that a SourceBuffer can only have either an interleaved
> audio/video track, or just audio or just video. I'm a bit confused
> about that, because SourceBuffer clearly talks about multiple audio
> and video tracks, and also about text tracks.
In theory, a SourceBuffer may indeed correspond to many multiplexed 
streams (audio(s)+video(s)+text track(s)+metadata track(s)). The text 
you quoted indicates minimal implementation requirements. 
Implementations are free to support more than that.


> Is this text left-over from the early days of the specification? Does
> it actually mean that you can either provide tracks in an interleaved
> manner or as separate SourceBuffers? OR do you really mean what is
> written there? If the latter, how then do you get multiple tracks and
> in particular text tracks into MediaSource ?
> Thanks for any clarification you can provide!
> Cheers,
> Silvia.

Cyril Concolato
Multimedia Group / Telecom ParisTech
Received on Monday, 20 October 2014 07:48:45 UTC

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