Apple

(Though I have to say that it feels weird to duplicate all of my note events with user events...)

Thanks again.

On 2012-02-28, at 7:58 AM, David Hicks wrote:

Hi James,
The first thing to note is that there arent too many of us MIDI guys on the CoreAudio list. And, not totally coincidentally, Apple isnt putting much effort into this end of their technology.

When I did my first OS X app, I didnt know about MusicSequence, and created my own Note and Track classes. It appears that Apple forces separate tracks from channels in loading SMFs, and my own data includes many multi-channel tracks, and so this would have bugged me. Though now I see MusicTrackMerge...

But Im working on a new app and am thinking about using the technique I mentioned. Since I have to analyze my tracks specifically to get Duration into my Note instances anyway, I think it wouldnt cost much to create a method that returns an array of all Notes, with durations, and another that adds UserEvents (and replaces NoteOn and NoteOff events with extendedNoteEvents??) to a track.

And, if I put the UserEvents in ahead of the (extendedNote) events, I could consult UI-generated changes (velocity, pitch) and change the note events (especially extendedNoteEvents, with duration!) on the fly, in the track, by using MusicTrackClear and AddNewExtendedNoteEvent. Id be jammin!

Well, good luck!
David

From: coreaudio-api-bounces+d.hicks=email@hidden [mailto:coreaudio-api-bounces+d.hicks=email@hidden] On Behalf Of James Maxwell
Sent: Tuesday, February 28, 2012 10:12 AM
To: email@hidden
Subject: Re: Grabbing MusicPlayer events during playback

Hi David,

Thanks for the tip. I had thought of using the user event/SequenceCallback system, but was kind of hoping somebody out there had some alternative magic! It just seems like a very fussy way to go about something that should be quite simple; i.e., adding events that are already all in the sequence, and are thus entirely redundant. I can see that this probably isn't a common request, but I know there have been plenty of posts here in the past by people wanting to "track" events during playback, which is basically what I'm trying to do. I wish Apple would add a simpler way...

I was wondering whether there might be a way to use the MusicEventIterator. For example, starting the iterator when MusicPlayer is started, then using MusicEventIteratorNextEvent to grab the coming event. I'd just store it until MusicPlayerGetTime (which I'd have to poll) returns a value greater than the event's time. It wouldn't be perfect, since the timing would depend on the poll rate, but the function I'm writing doesn't actually need perfect timing, it just needs to know what it's playing at any given time, so it can "think ahead", so to speak.

I'll look into both options, but if anybody has any other tricks they've used, I'd love to hear them.

Thanks again.

J.

On 2012-02-28, at 6:47 AM, David Hicks wrote:

James,

I havent done this, but it looks like it would work. If youre willing to fiddle with the events in your tracks, you could do this by adding UserEvents to a MusicSequences MusicTracks (at the same timestamps as your NoteOn events). If you analyze the track before playback and know the durations, you could add the duration info to these UserEvents. Then, with a SequenceCallback registered, you will get alerted at every UserEvent with your duration Info. See MusicSequence & MusicTrack references.

David

MusicSequenceSetUserCallback
Registers a user callback function with a music sequence.

OSStatus MusicSequenceSetUserCallback (

    MusicSequence              inSequence,

    MusicSequenceUserCallback inCallback,

    void                       *inClientData

);

Parameters
inSequence

The music sequence that you want to add a user callback function to.
inCallback

A reference to your callback function. Use NULL to remove a registered callback function.
inClientData

Your data that the music sequence provides back to your callback function when it is invoked.

Return Value
A result code.

Discussion
The music sequence invokes your callback for each user event added to any music track owned by the sequence. If there is a callback registered, then UserEvents will be chased when MusicPlayerSetTime is called. In that case the inStartSliceBeat and inEndSliceBeat will both be the same value and will be the beat that the player is chasing to.

MusicTrackNewUserEvent
Adds an event of type MusicEventUserData to a music track.

OSStatus MusicTrackNewUserEvent (

    MusicTrack                inTrack,

    MusicTimeStamp            inTimeStamp,

    const MusicEventUserData *inUserData

);

From: coreaudio-api-bounces+d.hicks=email@hidden [mailto:coreaudio-api-bounces+d.hicks=email@hidden] On Behalf Of James Maxwell
Sent: Monday, February 27, 2012 10:01 PM
To: email@hidden
Subject: Grabbing MusicPlayer events during playback

Hello All,

I'm wondering if there's a good way to grab MusicPlayer events within an application, during playback, **without** using a MIDI endpoint? I have a system that has to "listen" to its own playback, but I don't want to use the actual MIDI endpoint, in order to avoid feedback loops. Also, it would be great to be able to get the duration info, which I wouldn't normally have in "live" playback (i.e., I don't know when a note will end), but would have directly from the sequence/track. Any way to do this?

thanks,

J.

------------------------------------------------------

James B. Maxwell

Composer/Researcher/PhD Candidate

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James B. Maxwell

Composer/Researcher/PhD Candidate

------------------------------------------------------

James B. Maxwell

Composer/Researcher/PhD Candidate