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Re: Use-case for audio/video track mixing with ducking effect

From: Olivier Thereaux <olivier.thereaux@bbc.co.uk>
Date: Mon, 12 Mar 2012 15:42:58 +0000
Message-ID: <4F5E1982.1040506@bbc.co.uk>
To: public-audio@w3.org
CC: robert@ocallahan.org
Following this discussion, and a recent teleconference where we agreed 
it was a valuable use case, I have drafted text for UC15:

This should complete ACTION-35: Add use case for video sync, add 
requirement to work well with mediacontroller

Note that I haven't added a direct mention of MediaController in the use 
case prose itself, as it is an implementation detail and should probably 
not matter as far as usage scenarios are concerned? I have made a note 
of this in here, however:


Feedback on the use case text welcome.
I will be populating the related requirements for this use case shortly.



On 02/03/2012 13:45, Olivier Thereaux wrote:
> On 29/02/2012 23:41, Robert O'Callahan wrote:
>> The MediaStreams Processing document had a scenario which I think isn't
>> covered by the existing use-cases in the wiki: "Play video with
>> processing effects mixing in out-of-band audio tracks (in sync) (e.g.
>> mixing in an audio commentary with audio ducking)"
> Thanks for raising this, I believe you are right. We did go through the
> "heap" of all our sources of use cases and were due to review a few open
> questions, including this.
> See: http://www.w3.org/2011/audio/track/actions/28
> Chris wrote: “There was a requirement to "Seamlessly switch from one
> input stream to another (e.g. adaptive streaming)" which I think is out
> of scope for this group. ”
>> A very common example of this is DVD commentary tracks.
> Indeed, and not just commentary tracks. The BBC for instance is
> providing audio description for a number of its programmes, and the
> ability to start the audio description track in sync with the specific
> video timing, mix the two tracks and ideally duck the main audio track
> when the description track is "speaking" are realistic scenario.
>> A browser-oriented use-case could be: "User wants to play a video from a
>> Web site, with a third-party commentary track downloaded from another
>> site."
> Likewise for a number of multilingual content, where you could want to
> keep the original sound from an interview and have the dubbing track on
> top, with an appropriate amount of ducking.
> If I may deconstruct the issue here, could we say that this use case
> illustrates the need for:
> * Mixing sources
> * Ducking
> * Syncing sources/streams with other timed media and events
> Anything I forgot?
> I'd love to see demos of implementing this with the web audio API, and
> the approaches explained on the spec differences doc.
> Olivier

Olivier Thereaux
BBC Internet Research & Future Services

Received on Monday, 12 March 2012 15:43:46 UTC

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