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Re: Audio-ISSUE-33 (numberOfChannels): AudioDestinationNode.numberOfChannels [Web Audio API]

From: Philip Jägenstedt <philipj@opera.com>
Date: Fri, 25 May 2012 14:36:40 +0200
To: public-audio@w3.org
Message-ID: <op.weu6ne10sr6mfa@kirk>
On Thu, 24 May 2012 17:25:26 +0200, olivier Thereaux  
<olivier.thereaux@bbc.co.uk> wrote:

>
> On 15 May 2012, at 15:16, Audio Working Group Issue Tracker wrote:
>
>> Audio-ISSUE-33 (numberOfChannels):  
>> AudioDestinationNode.numberOfChannels [Web Audio API]
>>
>> http://www.w3.org/2011/audio/track/issues/33
>>
>> Raised by: Philip Jägenstedt
>> On product: Web Audio API
>>
>> It's not defined what numberOfChannels means, is it a constant value  
>> that depends on the underlying hardware or the maximum number of  
>> channels of all the inputs?
>>
>> More importantly, what is the use case for exposing this information?
>
> This issue is now Pending Review, per  
> https://dvcs.w3.org/hg/audio/rev/90e55985e260

As Marcus pointed out in  
<http://lists.w3.org/Archives/Public/public-audio/2012AprJun/0355.html>,  
maxNumberOfChannels doesn't seem to really work and an array of values  
would make more sense.

We don't think that setting numberOfChannels to a configuration that isn't  
supported should throw an exception, since that's likely to result in  
unhandled exceptions when authors have only tested with one speaker  
configuration. For example, it's to be expected that authors will set  
numberOfChannels to 2 without checking maxNumberOfChannels, which will  
fail on smartphones with a single speaker. Instead, we think that the  
requested number of channels should be used and mixing should be applied  
if the hardware doesn't support it.

Note also the typo in "If this value is 0, then this indicates that  
<code>maxNumberOfChannels</code>" which should be numberOfChannels.

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Friday, 25 May 2012 12:37:23 GMT

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