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Re: I/O support issue
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Re: I/O support issue


  • Subject: Re: I/O support issue
  • From: Howard Moon <email@hidden>
  • Date: Thu, 30 Sep 2004 14:13:25 -0700

On Sep 30, 2004, at 1:45 PM, Marc Poirier wrote:

On Sep 30, 2004, at 4:24 PM, Howard Moon wrote:

Hi,

I'm trying to get a audio unit to support mono only, but I'm having trouble doing so. I must be missing something somewhere. I'm returning just the single pair {1,1} for the kAudioUnitProperty_SupportedNumChannels property, but that doesn't seem to be sufficient. My audio unit still shows up on Stereo tracks (or as a mono-to-stereo plug-in in Logic), although it won't load because I check the stream format and report it as invalid if I get a stereo in or out stream.

How do I tell the host (specifically Logic or Digital Performer) that my AU only supports mono, in such a way that it doesn't appear on their menus for stereo tracks?

You didn't post your code so there's no way to comment on what you're doing, but here is sample code that will work:

UInt32 HowardPlug::SupportedNumChannels(const AUChannelInfo ** outChannelInfo)
{
static AUChannelInfo plugChannelInfo = {1, 1};
if (outChannelInfo != NULL)
*outChannelInfo = &plugChannelInfo;

return 1;
}

That looks just about like mine:

<x-tad-smaller>UInt32 MyPlugin::SupportedNumChannels(const AUChannelInfo** ppArray)
{
static const AUChannelInfo asChannelInfo[] =
{1,1}; // for stereo: {{1,1},{1,2},{2,2}};
if (ppArray)
*ppArray=asChannelInfo;
return 1; // for stereo: 3;
}
</x-tad-smaller>

But it still shows up in the menu of a stereo track in DP4, and in the mono->stereo menu in Logic. There must be something else involved somewhere...?

-Howard


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References: 
 >I/O support issue (From: Howard Moon <email@hidden>)
 >Re: I/O support issue (From: Marc Poirier <email@hidden>)

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