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How to change MIDI TEMPO on the fly? [CoreMIDI] iOS

I have a MusicTrack with MIDI Notes set to MusicSequence playing with MusicPlayer. The problem occurs when I tried to adjust the tempo using

MusicTrackNewExtendedTempoEvent (musicTrack, 0.0, newBPM);

Apparently this should change the TempoEvent in the MusicTrack that's playing, but it isn't. Any idea why this might be happening?

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1 answer


First you need to remove all tempo events from the tempo track.



static void removeTempoEvents(MusicTrack tempoTrack){
    MusicEventIterator tempIter;
    NewMusicEventIterator(tempoTrack, &tempIter);
    Boolean hasEvent;
    MusicEventIteratorHasCurrentEvent(tempIter, &hasEvent);
    while (hasEvent) {
        MusicTimeStamp stamp;
        MusicEventType type;
        const void *data = NULL;
        UInt32 sizeData;

        MusicEventIteratorGetEventInfo(tempIter, &stamp, &type, &data, &sizeData);
        if (type == kMusicEventType_ExtendedTempo){
            MusicEventIteratorDeleteEvent(tempIter);
            MusicEventIteratorHasCurrentEvent(tempIter, &hasEvent);
        }
        else{
            MusicEventIteratorNextEvent(tempIter);
            MusicEventIteratorHasCurrentEvent(tempIter, &hasEvent);
        }
    }
    DisposeMusicEventIterator(tempIter);
}
static void setTempo(MusicSequence sequence,Float64 tempo){
    MusicTrack tempoTrack;
    MusicSequenceGetTempoTrack(sequence ,&tempoTrack);
    removeTempoEvents(tempoTrack);
    MusicTrackNewExtendedTempoEvent(tempoTrack,0, tempo);
}
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