Re: How to deal with kAudioFormatMIDIStream format?
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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