[seq24-users] seq24 & OSX

[c h. <cal...@ho...>]

I made a bit of a foray into this a few months ago, but got caught up with 
other things.  Here's what I found.

The CoreMidi/AudioToolbox classes of most immmediate interest are 
MIDIEndpointRef, MusicSequence, MusicTrack, MIDINoteMessage, and MusicPlayer 
(anyone interested should have a look at <AudioToolbox/AudioToolbox.h> and 
<CoreMIDI/MIDIServices.h>).  A Music Player is used to control the playing 
of a MusicSequence and is associated with at most one Music Sequence (which 
can also only be associated with one MusicPlayer).  MusicSequences are 
associated with a single MIDIEndpointRef (midi device), and contain 
MusicTracks, which in turn contain events such as MIDINoteMessages.  In a 
departure from the Seq24 model, midi channel information is associated with 
events rather than tracks.  The analogy between master/midibus and 
MIDIEndPointRef is also not perfect.  Not having programmed with alsa, I'm 
not sure what an Alsa sequencer client's responsibilities are.  I thought it 
might be more or less equivalent to a MusicPlayer.

Therefore, I thought the following Seq24/Alsa:CoreMidi correspondences might 
provide a starting point:

event -> MIDINoteMessage
sequence -> MusicTrack
perform -> MusicSequence
mastermidibus/midibus (?) -> MIDIEndPointRef
snd_seq_t* -> MusicPlayer

Initially I managed to eliminate all the Alsa dependencies (compiled and ran 
but didn't do much).  Then, as a quick hack, I thought I'd make Seq24 
objects wrapper for the corresponding CoreMidi objects.  A few other things 
had to be shifted around to account for the discrepancies between the two 
models.  I've managed to send some midi to my synth, but haven't been too 
thorough, and really all I have are some rudimentary tinkerings.  I'd be 
interested in helping to port Seq24 as time permits.

Cheers,
Callum.

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