在 C++ 项目中使用 (OSX) 核心 MIDI

Question

这是 Core Midi 的 (Objective C) 文档：https://developer.apple.com/documentation/coremidi

我如何才能了解在 C++ 项目中使用它的期望？

（我想还有一个更基本的问题：Can I use Core MIDI in a C++ project? - 但我已经看到其他 Whosebug 问题，答案似乎是 "yes" [然后，那些是几年前的...])

我需要做什么才能完成此设置 - 到可以开始使用 API 的地步？文档并没有说明使用了什么框架，需要什么头文件等等...

那么，开始的步骤是什么？

理想情况下，我希望能够从一个简单的 makefile 进行编译。

Answer 1

大部分 CoreMIDI API 是普通的旧 C。您可以轻松地从 C++ 代码调用它，而无需执行任何特殊操作。

（Apple 文档在 "Swift" 和 "Objective-C" 之间切换语言，但不要按字面意思理解 "Objective-C"。它的真正意思是 "C family, either C or Objective-C"。将其切换为Swift 向您显示相同的 API，但以 Swift 可见的翻译形式显示。）

具体见CoreMIDI/MIDIServices.h。

最古老和最简单的 CoreMIDI 示例代码 "Echo.cpp" 实际上是 C++。它从所有源读取 MIDI 输入并将该 MIDI 数据发送到第一个可用目的地（在通道 1 上）。这很粗糙，但你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=%s\n", name, manuf, model);
    }

    // open connections from all sources
    n = MIDIGetNumberOfSources();
    printf("%d sources\n", 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 %s\n", gChannel + 1, name);
    } else {
        printf("No MIDI destinations present\n");
    }

    CFRunLoopRun();
    // run until aborted with control-C

    return 0;
}

在 C++ 项目中使用 (OSX) 核心 MIDI

Using (OSX) Core MIDI in a c++ project

c++

objective-c

macos

coremidi