使用CoreMidi的MIDI文件的速度

我想知道如何使用CoreMidi框架找到midi文件的节奏。据我所知 MusicSequence 类用于打开midi文件。它包含许多曲目,包括类型为的节奏曲目 MusicTrack 在检查MusicTrack类时,似乎没有任何参数或方法可以实际获得节奏。我从中得到以下代码 site …这是代码:

-(void) openMidiFile {
    MusicSequence sequence;
    NewMusicSequence(&sequence);

    NSURL *midiFileURL = [[NSBundle mainBundle] URLForResource:@"bach-invention-01" withExtension:@"mid"];

    MusicSequenceFileLoad(sequence, (__bridge CFURLRef)midiFileURL, 0,
                      kMusicSequenceLoadSMF_ChannelsToTracks); //needs to change later

    MusicTrack tempoTrack;
    MusicSequenceGetTempoTrack(sequence, &tempoTrack);

    MusicEventIterator iterator;
    NewMusicEventIterator(tempoTrack, &iterator);

    Boolean hasNext = YES;
    MusicTimeStamp timestamp = 0;
    MusicEventType eventType = 0;
    const void *eventData = NULL;
    UInt32 eventDataSize = 0;

    // Run the loop
    MusicEventIteratorHasCurrentEvent(iterator, &hasNext);
    while (hasNext) {
        MusicEventIteratorGetEventInfo(iterator,
                                   &timestamp,
                                   &eventType,
                                   &eventData,
                                   &eventDataSize);

        // Process each event here
        printf("Event found! type: %d\n", eventType); //tempo occurs when eventType is 3
        printf("Event data: %d\n", (int)eventData); //data for tempo?

        MusicEventIteratorNextEvent(iterator);
        MusicEventIteratorHasCurrentEvent(iterator, &hasNext);
    }
}