Re: Multiple Output Music Device
Re: Multiple Output Music Device
- Subject: Re: Multiple Output Music Device
- From: Art Gillespie <email@hidden>
- Date: Fri, 17 Oct 2003 08:12:10 -0400
Thanks for the info, Bill.
This is a bit tricky as the num channels property is only really
generally used to describe a common channel capability across all
busses/elements.
Right. Completely misunderstood this property, I guess. So, to
clarify: A four-stereo-bus output synth would return { 0, 2 } in
response to kAudioUnitProperty_SupportedNumChannels. Or, to use my
somewhat contrived example of the 2+2+1+1 four-bus configuration, the
AudioUnit shouldn't respond to kAudioUnitProperty_SupportedNumChannels,
but handle the negotiation completely with
kAudioUnitProperty_StreamFormat?
This is definitely wrong, as not a single bus can be set to 6
channels. Part of the motivation of having this property was to
describe alternate settings of channelisations (Which this is not
really a case of). Can I ask this - why are you providing 2 stereo
pairs and 2 mono outputs?
It was a hypothetical, I chose that configuration in my example simply
because it's non-uniform between busses. However, I wasn't thinking in
terms of surround or speakers, but rather auxiliary outputs for say, a
sample-playback device.
In that case this really should be a single six channel output. We've
defined (and discussed previously) the AudioChannelLayout structure
that provides meta data about the channel ordering where a stream
description only describes the number of channels. This is also
described in the Panther SDK.
Right, saw that, but it seemed more geared towards multi-channel
panners and describing multi-channel file layouts. If I understand the
AU semantics correctly, busses are more appropriate for auxiliary
outputs on a sampler... or does the new AudioChannelLayout descriptor
suit this application better? Should we be piling all our channels
into a single bus and giving them meaning via AudioChannelLayout?
Best,
Art
>>0xBA
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