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Re: Multi-channel hardware support available for testing in Chrome Canary

From: Jory <me@jory.org>
Date: Fri, 15 Mar 2013 10:47:14 -0700
Message-Id: <CD0E2BD4-4A99-4562-ADA7-BF1973FF4A15@jory.org>
To: "public-audio-dev@w3.org" <public-audio-dev@w3.org>
I spent a lot of time reading through that part of the spec lat night, but to no avail. I didn't try the ChannelMergerNode, so I'll give that a shot.

Something that was completely unclear to me was what output.L, output.R, output.C, etc referred to. Where is output coming from? I didn't see anything like that in any of the examples elsewhere, nor could I found anything that subdivided channels inside the Inspector in Canary.

Also, should multichannel audio files play? If so, what formats?

Jory

me@jory.org
http://studio.jory.org

On Mar 15, 2013, at 10:34, Chris Rogers <crogers@google.com> wrote:

> 
> 
> 
> On Thu, Mar 14, 2013 at 11:11 PM, Jory <me@jory.org> wrote:
>> On Thu, 14 Mar 2013 15:53:50 -0700, Chris Rogers wrote:
>> > For those interested in multi-channel output in the Web Audio API, here's
>> > your chance to try out an early build.  This could be of interest for
>> > digital DJ type applications, or rendering to multi-channel speaker
>> > installations...
>> >
>> > Please note this is an early build and little testing has yet been made.
>> >  So far I've tested on several devices on OSX.  I'm interested in your
>> > feedback!
>> >
>> > The .maxChannelCount attribute is now exposed to show the actual number of
>> > hardware channels:
>> >
>> https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#AudioDestinationNode
>> >
>> > The .channelCount attribute should now be settable on the
>> > AudioDestinationNode to values up to .maxChannelCount
>> >
>> > Cheers,
>> > Chris
>> 
>> Well, I've spent a couple hours playing around, since multichannel
>> audio certainly interests me, both for games and music. I've had very
>> little success, though.
>> 
>> I'm finding it very difficult to get any audio to play out anything but
>> the Left and Right channels. The only success I've had was forcing a
>> down-mix to 1 channel, where sound finally came out my Center channel.
>> So clearly the system functions in some manner. I've tried setting up a
>> 3D panner and hard-coding positional panning, but sound never leaves my
>> Lft-Rht channels.
> 
> Hi Jory, I believe Chris Wilson will be writing an article with more details and complete sample code.  In the meantime, you can look at some of the partial example code here:
> https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#UpMix
> 
> Just to add a little more detail, with the "digital DJ" example you'd want to use a ChannelMergerNode to combine two separate stereo mixes.  The first one would be connected to input 0 of the merger and the 2nd to input 1.  Then the merger would be connected to the destination as configured in the partial example code.
> 
> The ChannelMergerNode turns out to be really important for these types of applications.  In another example, if your hardware supported 8 channels of output, you could configure it as 8-channel discrete, then create a merger and connect eight independent mono AudioNodes to inputs 0 - 7 of the merger.  Then you could hookup eight speakers and place them anywhere in the room you like.  And the mono sources could be whatever you want - maybe 8 de-correlated channels of white noise...
> 
> Hope that helps.
> 
>  
>> 
>> I also tried playing back a 6-channel interleaved WAV file, but while
>> the file appears to "play", sound doesn't come from any speaker, no
>> matter how I try to configure the channelCount.
>> 
>> I'm beginning to wonder if 6-channel source files are playable at this
>> time or if that's unsupported. (Everything seems to have choked when I
>> supplied a 6-channel AAC file, but I'm not even 100% the file I
>> supplied was even playable, since getting multi-channel AAC output is
>> kinda challenging with today's tools.) Also, a bit of sample code would
>> do my morale wonders right about now. :-)
>> 
>> Thanks!
>> 
>> Jory
>> 
>> me@jory.org
>> http://studio.jory.org
> 
Received on Friday, 15 March 2013 17:47:51 GMT

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