IOS MusicSequence & MusicPlayer 外部 MIDI 时钟同步

Question

我正在使用 MusicPlayer 在 MusicSequence 中播放音符：

NewMusicSequence(&sequence);
MusicSequenceFileLoad(sequence, (__bridge CFURLRef) midiFileURL, 0, 0);

// Set the endpoint of the sequence to be our virtual endpoint
MusicSequenceSetMIDIEndpoint(sequence, virtualEndpoint);

// Create a new music player
MusicPlayer  p;

// Initialise the music player
NewMusicPlayer(&p); 


// Load the sequence into the music player
MusicPlayerSetSequence(self.player, sequence);
// Called to do some MusicPlayer setup. This just
// reduces latency when MusicPlayerStart is called
MusicPlayerPreroll(self.player);

-(void)play {
   MusicPlayerStart(self.player);
}

它工作得很好，我会说很好，但我不想使用内部时钟。

如何使用外部 MIDI 时钟？
或者也许我可以用时钟移动播放光标。

Answer 1

你可以使用 MusicSequenceSetMIDIEndpoint(sequence,endpointRef);

然后创建一个MIDI时钟

 CAClockRef mtcClockRef;
    OSStatus err;
      err = CAClockNew(0, &mtcClockRef);
            if (err != noErr) {
                NSLog(@"\t\terror %ld at CAClockNew()", err);
            }
            else {
                CAClockTimebase timebase = kCAClockTimebase_HostTime;
                UInt32 size = 0;
                size = sizeof(timebase);
                err = CAClockSetProperty(mtcClockRef, kCAClockProperty_InternalTimebase, size, &timebase);
                if (err)
                    NSLog(@"Error setting clock timebase");

设置同步模式

UInt32 tSyncMode = kCAClockSyncMode_MIDIClockTransport;
                size = sizeof(tSyncMode);
                err = CAClockSetProperty(mtcClockRef, kCAClockProperty_SyncMode, size, &tSyncMode);

然后将时钟设置为使用 midi 端点

 err = CAClockSetProperty(mtcClockRef, kCAClockProperty_SyncSource, sizeof(endpointRef), endpointRef);

这里有一些参考代码 VVMIDINode -> https://github.com/mrRay/vvopensource/blob/master/VVMIDI/FrameworkSrc/VVMIDINode.h