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Re: Audio-ISSUE-12 (Joe Berkovitz): Loop start/stop points [Web Audio API]

From: Olivier Thereaux <olivier.thereaux@bbc.co.uk>
Date: Wed, 02 May 2012 14:16:21 +0100
Message-ID: <4FA133A5.30708@bbc.co.uk>
To: public-audio@w3.org
CC: Joseph Berkovitz <joe@noteflight.com>
Hi Joe,


On 30/04/2012 17:31, Audio Working Group Issue Tracker wrote:
> Audio-ISSUE-12 (Joe Berkovitz): Loop start/stop points [Web Audio API]
>
> http://www.w3.org/2011/audio/track/issues/12
>
> Raised by: Joe Berkovitz
> On product: Web Audio API
>
> Hi folks,
>
> At the F2F in January we discussed the need for a more powerful looping construct in AudioBufferSourceNode than simply "loop the whole sound", in order to support UC6 (wavetable synthesis) and other user cases.

Indeed. The current requirement text specifies:
“A subrange of a source can be played. It should be possible to start 
and stop playing a source of audio at any desired offset within the 
source. This would then allow the source to be used as an audio sprite”
http://www.w3.org/2011/audio/wiki/Use_Cases_and_Requirements#Playing_.2F_Looping__sources_of_audio


> I am proposing that there be separate loopStart and loopEnd properties of AudioBufferSourceNode that are sample-accurate.  If respectively set to 0 and the length of the sample, these will cause the entire sample to be looped.  If set to offsets M and N, these will cause the sample to be played by noteOn() and noteGrainOn() as if the sample consisted of contiguous subranges [0..M-1], [M..N], [M..N], ...

The properties should probably be optional, with 0 / full length as 
default if not specified.

Olivier



Received on Wednesday, 2 May 2012 13:16:50 GMT

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