在C 项目中使用(OSX）Core MIDI

大多数Coremidi API都是旧的。

（Apple文档在" Swift"answers" Objective-C"之间有一种语言，但不要从字面上看" Objective-C"。这确实是指" C家族，C或Objective-C"。切换Swift向您显示了相同的API，但以Swift可见的翻译形式。）

具体来说，请参见Coremidi/Midiservices.H。

实际上是C 的最古老，最简单的Coremidi样品代码" echo.cpp"。它读取所有来源的MIDI输入，并将该MIDI数据发送到第一个可用目的地（在频道1上）。这很粗糙，但是您必须从某个地方开始。

编译：

clang Echo.cpp -framework CoreMIDI -framework CoreFoundation -o Echo

代码：

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#include <CoreMIDI/MIDIServices.h>
#include <CoreFoundation/CFRunLoop.h>
#include <stdio.h>
// ___________________________________________________________________________________________
// test program to echo MIDI In to Out
// ___________________________________________________________________________________________
MIDIPortRef     gOutPort = NULL;
MIDIEndpointRef gDest = NULL;
int             gChannel = 0;
static void MyReadProc(const MIDIPacketList *pktlist, void *refCon, void *connRefCon)
{
    if (gOutPort != NULL && gDest != NULL) {
        MIDIPacket *packet = (MIDIPacket *)pktlist->packet; // remove const (!)
        for (unsigned int j = 0; j < pktlist->numPackets; ++j) {
            for (int i = 0; i < packet->length; ++i) {
//              printf("%02X ", packet->data[i]);
                // rechannelize status bytes
                if (packet->data[i] >= 0x80 && packet->data[i] < 0xF0)
                    packet->data[i] = (packet->data[i] & 0xF0) | gChannel;
            }
//          printf("n");
            packet = MIDIPacketNext(packet);
        }
        MIDISend(gOutPort, gDest, pktlist);
    }
}
int     main(int argc, char *argv[])
{
    if (argc >= 2) {
        // first argument, if present, is the MIDI channel number to echo to (1-16)
        sscanf(argv[1], "%d", &gChannel);
        if (gChannel < 1) gChannel = 1;
        else if (gChannel > 16) gChannel = 16;
        --gChannel; // convert to 0-15
    }
    // create client and ports
    MIDIClientRef client = NULL;
    MIDIClientCreate(CFSTR("MIDI Echo"), NULL, NULL, &client);
    MIDIPortRef inPort = NULL;
    MIDIInputPortCreate(client, CFSTR("Input port"), MyReadProc, NULL, &inPort);
    MIDIOutputPortCreate(client, CFSTR("Output port"), &gOutPort);
    // enumerate devices (not really related to purpose of the echo program
    // but shows how to get information about devices)
    int i, n;
    CFStringRef pname, pmanuf, pmodel;
    char name[64], manuf[64], model[64];
    n = MIDIGetNumberOfDevices();
    for (i = 0; i < n; ++i) {
        MIDIDeviceRef dev = MIDIGetDevice(i);
        MIDIObjectGetStringProperty(dev, kMIDIPropertyName, &pname);
        MIDIObjectGetStringProperty(dev, kMIDIPropertyManufacturer, &pmanuf);
        MIDIObjectGetStringProperty(dev, kMIDIPropertyModel, &pmodel);
        CFStringGetCString(pname, name, sizeof(name), 0);
        CFStringGetCString(pmanuf, manuf, sizeof(manuf), 0);
        CFStringGetCString(pmodel, model, sizeof(model), 0);
        CFRelease(pname);
        CFRelease(pmanuf);
        CFRelease(pmodel);
        printf("name=%s, manuf=%s, model=%sn", name, manuf, model);
    }
    // open connections from all sources
    n = MIDIGetNumberOfSources();
    printf("%d sourcesn", n);
    for (i = 0; i < n; ++i) {
        MIDIEndpointRef src = MIDIGetSource(i);
        MIDIPortConnectSource(inPort, src, NULL);
    }
    // find the first destination
    n = MIDIGetNumberOfDestinations();
    if (n > 0)
        gDest = MIDIGetDestination(0);
    if (gDest != NULL) {
        MIDIObjectGetStringProperty(gDest, kMIDIPropertyName, &pname);
        CFStringGetCString(pname, name, sizeof(name), 0);
        CFRelease(pname);
        printf("Echoing to channel %d of %sn", gChannel + 1, name);
    } else {
        printf("No MIDI destinations presentn");
    }
    CFRunLoopRun();
    // run until aborted with control-C
    return 0;
}