Re: Can Audio Units be MIDI processors?
Re: Can Audio Units be MIDI processors?
- Subject: Re: Can Audio Units be MIDI processors?
- From: William Stewart <email@hidden>
- Date: Tue, 13 Mar 2007 12:14:44 -0700
- Delivered-to: email@hidden
- Delivered-to: email@hidden
We've just added an AU property for this for Leopard - here's a
preview of how this looks:
@constant kAudioUnitProperty_MIDIOutputCallback
Scope: Global
Value Type: AUMIDIOutputCallbackStruct
Access: write
The host sets this property on the audio unit with the callback
(and its user data) set
appropriately.
Operational Parameters:
In the render call, just as is the expected usage of the
AUHostCallbacks, the audio unit can
call the provided callback to provide MIDI data to the host
that it will associate with the
current AudioUnitRender call in process.
The audio unit in the callback provides:
- the user data provided by the host when the callback was
established
- the AudioTimeStamp that was provided to the audio unit for
this particular call of
AudioUnitRender
- the output number to associate this MIDI data with
- a MIDI Packet List containing MIDI data. The time stamp
values contained within the
MIDIPackets in this list are **sample offsets*** from the
AudioTimeStamp provided.
This allows MIDI data to be time-stamped with a sample offset
that is directly associated
with the audio data it is generating in the current call to
the AudioUnitRender function
There is no implied or expected association between the number
(or position) of an audio unit's
audio or MIDI outputs.
/*
@typedef AUMIDIOutputCallback
@abstract A callback used by an audio unit to provide MIDI data to
a host application
*/
typedef OSStatus
(*AUMIDIOutputCallback)(void * userData,
const AudioTimeStamp * timeStamp,
UInt32 midiOutNum,
const struct MIDIPacketList * pktlist);
/*!
@struct AUMIDIOutputCallbackStruct
@abstract Set by host application to provide the callback and user
data for an audio
unit that provides MIDI output
*/
typedef struct AUMIDIOutputCallbackStruct {
AUMIDIOutputCallback midiOutputCallback;
void* userData;
} AUMIDIOutputCallbackStruct;
On 01/03/2007, at 3:21 PM, Stephen Kay wrote:
Hi, I came late to the game, sorry if this is a stupid question,
I've been
looking at the docs a little and it's not clear to me...
I'd like to know if an AU can be written that takes MIDI In, and
spits more
MIDI out in real-time, like an arpeggiator, with the idea that the
plug-in
produces no Audio of its own, but simply generates MIDI to be
routed to
other plug-ins.
If so, any pointers to some relevant example source or
documentation would
be truly helpful.
Thanks!
- Stephen
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Stephen Kay
Karma-Lab :: developers of KARMA
http://www.karma-lab.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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