W3C home > Mailing lists > Public > public-html-media@w3.org > October 2014

Re: Clarification of addSourceBuffer() method

From: Cyril Concolato <cyril.concolato@telecom-paristech.fr>
Date: Mon, 20 Oct 2014 12:10:57 +0200
Message-ID: <5444DFB1.3090003@telecom-paristech.fr>
To: public-html-media@w3.org
Le 20/10/2014 11:36, Silvia Pfeiffer a écrit :
> On Mon, Oct 20, 2014 at 6:48 PM, Cyril Concolato
> <cyril.concolato@telecom-paristech.fr> wrote:
>> 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.
> Ah thanks for clarifying.
> It's still quite confusing actually. In particular the point about
> returning two SourceBuffers where the return value of the method is
> merely a SourceBuffer object. Can you explain how that is going to
> work, too?
addSourceBuffer always returns a single SourceBuffer. The text above is 
meant to say that implementations should support either one call to 
addSourceBuffer for multiplexed a/v streams or two calls for separate 
audio and video streams and that it may throw a QUOTA_EXCEEDED_ERROR on 
the next calls.


Cyril Concolato
Multimedia Group / Telecom ParisTech
Received on Monday, 20 October 2014 10:11:21 UTC

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