Re: ScriptProcessorNode.channelCountMode should be explicit by default

On Sat, May 4, 2013 at 10:12 AM, Chris Rogers <crogers@google.com> wrote:

> On Tue, Apr 30, 2013 at 5:37 PM, Robert O'Callahan <robert@ocallahan.org>wrote:
>
>> Oops, I was right the first time and sloppy in what I just wrote. Rather
>> than make the channel count default to the UA's guess of the speaker
>> configuration, I think we can have the best of both worlds by making the
>> DestinationNode channelCountMode default to "max" and ensure the UA
>> downmixes that to the user's speaker configuration as necessary. That way,
>> Web Audio behavior as observed by Web applications does not default to
>> depending on the user's speaker configuration. But on the other hand, a Web
>> Audio application can produce surround sound just by sending 6 channels to
>> the DestinationNode, without having to do anything else. This will be
>> particularly helpful when the UA's speaker configuration changes
>> dynamically.
>>
>
> I see.  That might be possible, but we'd have to be very careful to think
> about all the possibilities.  Sometimes audio hardware has more than two
> channels, but is not necessarily connected to a multi-channel speaker
> system.  For example, my system at home is a multi-channel device, but I
> often only have the first two channels connected to a stereo playback
> system.  I'd like to preserve the current behavior for those kind of cases.
>

It has to be the UA's responsibility to determine what your speaker
configuration is and mix multichannel audio for that configuration
correctly. The UA has to be able to do this anyway to play multichannel
resources through an HTML media element. And of course a Web application
can't do it. (I suppose a Web application could ask the user, but it seems
obviously bad to have Web apps all independently asking for this
information.)

The UA is going to have to do this using some combination of OS features,
guesswork, and UI. How that works is out of scope for this spec. If the UA
can't determine the speaker setup with sufficient confidence, it may be
reasonable to default to a stereo configuration (which is what I think
you're suggesting), but that should be a UA-specfic policy.

Rob
-- 
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