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Re: How to deal with kAudioFormatMIDIStream format?
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Re: How to deal with kAudioFormatMIDIStream format?


  • Subject: Re: How to deal with kAudioFormatMIDIStream format?
  • From: William Stewart <email@hidden>
  • Date: Tue, 1 Mar 2005 10:45:55 -0800

We've had some further thoughts about this since those emails (and though this is pre-empting a planned future discussion, I can give you some details about those).

Basically, we believe both for hosts with existing AU and hosting logic, as well as the SDK classes, that to mix in MIDI into the current Input and Output scope would be too confusing.

So, what we will do is the following:
(1) Input and Output scope will be taken to mean audio data input and output scopes respectively. This ensures that existing AU"s will continue to work as they do today, and existing host logic will also remain unchanged


(2) We'll introduce a new MIDIInput and MIDIOutput pair of scopes. The elements on these two scopes will contain the data format as we previously described -= an ASBD with the 'midi' format type

Then, if a host wants to provide support for MIDI Data parsing, it can look for AU's that contain elements in these new scopes (as of course this type of data would require a distinct data path from the existing audio data).

There are actually still some details that we want to thrash out (and an example implementation); I thought it would be worthwhile regardless of that to describe the general thrust of our thinking.

Bill

On 01/03/2005, at 9:13 AM, Pavol Markovic wrote:

Hello,
I'd like to output MIDI data from AudioUnit to host or external device using standard "plug-in way" without creating virtual destinations or managing list of MIDI output destinations.


How can one deal with kAudioFormatMIDIStream format. I've found an older Pre-Panther discussion on this topic - http://lists.apple.com/archives/coreaudio-api/2003/Sep/msg00223.html - but I'd like to find out more information. There is no mention on this in AU Documentation, only definition in CoreAudio/CoreAudioTypes.h header.

So my initial thoughts are that I:
1. create on one more output bus (audio outputs buses + 1) and set kAudioFormatMIDIStream = 'midi' as format for it in constructor
2. set bus count read only
3. feed the output with MIDI data in Render call


Now, which hosts do currently support this?

I'm also curious in (kAudioFormatTimeCode = 'time'), how is this supported and what is it's exact purpose.

Thanks in advance,
Pavol Markovic

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References: 
 >How to deal with kAudioFormatMIDIStream format? (From: Pavol Markovic <email@hidden>)

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