Re: Implementing AudioChannelLayout property
Re: Implementing AudioChannelLayout property
- Subject: Re: Implementing AudioChannelLayout property
- From: William Stewart <email@hidden>
- Date: Mon, 17 Oct 2005 10:19:20 -0700
On 16/10/2005, at 10:51 PM, Pavol Markovic wrote:
Hello,
I'd like to add AudioChannelLayout support in our AU instrument. It
supports 5.1 which is corresponding to
kAudioChannelLayoutTag_AudioUnit_5_1.
I went though framework headers and AUBase source code and I'd like
to verify my step.
First as channel layout is per element, one has to subclass
AUOutputElement with own class implementing:
GetChannelLayoutTags
GetAudioChannelLayout
Yes - these are required of course
SetAudioChannelLayout (this one is questionable if propery is
readonly).
also override AUBase's CreateElement() method and return subclassed
elements here.
Are these steps correct?
yes
I have one more question: because layout tags are related to number
of channels, is audiounit's responsibility to change layout tag
everytime the number of channels is changed?
(To override element's SetStreamFormat and check for channel count
in description - and set kAudioChannelLayoutTag_Stereo for 2
channels and kAudioChannelLayoutTag_AudioUnit_5_1 for 6 channels?)
Its typically been done as a read/write property - so the host would
write the layout when it changes the format. The host's
responsibility is to set the format first, then the layout should
just follow it. If this is read only, then you should manange that
(so the layout will always follow the format).
Also I don't see 5.1 (also 6.1 and 7.1) tag checking included in
auval.
They aren't listed... As the LFE channel is really an effect channel
in itself (Low Freq Effects), we didn't expect that many AUs would
actually include this in their processing - in many cases its not
appropriate.
Bill
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