xcode - MIDIThruConnection创建xcode

Question

我用 coreMIDI 和 Xcode 对“MIDIThruConnectionCreate”进行了尝试，但它不起作用。MIDI In 和 MIDI Out 工作正常，但 MIDI Thru 不工作。感谢您的帮助。

- (void) midiThru
{
    MIDIThruConnectionParams params;
    CFDataRef dataRef;

    #if __LP64__
        typedef MIDIObjectRef MIDIThruConnectionRef;
    #else
        typedef struct OpaqueMIDIThruConnection * MIDIThruConnectionRef;
    #endif

    MIDIThruConnectionRef thru;

    MIDIThruConnectionParamsInitialize(&params);
    params.numSources = 1;
    params.sources[0].endpointRef = sourceMIDI;
    params.numDestinations = 1;
    params.destinations[0].endpointRef = destMIDI;
    dataRef = CFDataCreate(NULL, (unsigned char*) &params,
                                 sizeof(MIDIThruConnectionParams));
    s = MIDIThruConnectionCreate(NULL, dataRef, &thru);

    CFRelease(dataRef);
}