MIDINoteMessage 何时在 MusicTrack 中播放？ iOS

Question

我正在创建使用

成功播放的 MIDI 音符的 MusicTrack

MusicPlayerStart(sequencePlayer)

但我想知道它们什么时候播放，所以我可以为每个播放的 MIDI 音符更新 UI。

// Creating MIDI Track
MusicTrack track;
UInt32 trackIndex = 0;
musicTrackAtIndex(trackIndex, &track);

//Adding Tempo
addTempoEvent(0.0, 120);

// Adding MIDI notes
const int channel = 0;
MIDINoteMessage note;
note.channel = channel;
note.velocity = 100.0;
note.duration = 0.3;
note.releaseVelocity = 0;

note.note = 68;
addMIDINoteToTrack(track, note, 1);

note.note = 78;
addMIDINoteToTrack(track, note, 2);

note.note = 88;
addMIDINoteToTrack(track, note, 3);

note.note = 98;
addMIDINoteToTrack(track, note, 4);

MusicTimeStamp trackEnd = 4;
addEndOfTrackAtTime(trackEnd);

setLoopTrack(true); 

playSequence();

EDIT

更详细地展示了我是如何构建 MIDI 轨道的。

-(void) playing4NotesInLoop {

MusicTrack musicTrack;
MusicSequence musicSequence;
MusicPlayer musicPlayer;

const int loop_length = 4;

NewMusicSequence(&musicSequence);

// Create a client
MIDIClientRef virtualMidi;
MIDIClientCreate(CFSTR("Virtual Client"),
                          MyMIDINotifyProc,
                          NULL,
                          &virtualMidi);


// Create an endpoint
MIDIEndpointRef virtualEndpoint;
MIDIDestinationCreate(virtualMidi, @"Virtual Destination", MyMIDIReadProc, self.samplerUnit, &virtualEndpoint);


MusicSequenceNewTrack(musicSequence, &musicTrack);

MIDINoteMessage aMessage;
aMessage.channel = 1;

aMessage.duration = 0.5f;
aMessage.velocity = 100;

for(int i=0; i<4; ++i)
{
    if (i==0) {
        aMessage.note = 30;
    }else {
        aMessage.note = 60;
    }

    MusicTrackNewMIDINoteEvent(musicTrack, i, &aMessage);
}

MusicTrackLoopInfo loop_info;
loop_info.loopDuration = loop_length;
loop_info.numberOfLoops = 0;

MusicTrackSetProperty(musicTrack, kSequenceTrackProperty_LoopInfo, &loop_info, sizeof(MusicTrackLoopInfo));

MusicTimeStamp track_length;
track_length = loop_length;

MusicTrackSetProperty(musicTrack, kSequenceTrackProperty_TrackLength, &track_length, sizeof(MusicTimeStamp));

MusicSequenceSetMIDIEndpoint(musicSequence, virtualEndpoint);

NewMusicPlayer(&musicPlayer);
MusicPlayerSetSequence(musicPlayer, musicSequence);

MusicPlayerStart(musicPlayer);

}

使用这段代码，我成功地播放了一个 4 个音符的循环，一个 MusicSequenceSetMIDIEndpoint(musicSequence, virtualEndpoint) 已经设置好指定读取过程。我使用了相同的代码，但加载了一个 MIDI 文件并为每个音符成功调用了读取过程。

Answer 1

您使用 MIDIDestinationCreate 创建一个虚拟端点，然后调用 MusicSequenceSetMIDIEndpoint 将您的序列连接到它。您指定的读取过程将在每个事件上调用。

MIDINoteMessage 何时在 MusicTrack 中播放？ iOS

When is a MIDINoteMessage played in a MusicTrack? iOS

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