Question

这是一个发送MIDI数据的极其简单的CoreMIDI OS X应用程序。问题是它不起作用。编译好，并运行。它报告没有错误，并且不会崩溃。创建的源在MIDI监视器中可见。但是，没有MIDI数据出现。

有人能让我知道我在这里做错了吗？

#include <CoreMIDI/CoreMIDI.h>

int main(int argc, char *args[])
{
    MIDIClientRef   theMidiClient;
    MIDIEndpointRef midiOut;
    MIDIPortRef     outPort;
    char pktBuffer[1024];
    MIDIPacketList* pktList = (MIDIPacketList*) pktBuffer;
    MIDIPacket     *pkt;
    Byte            midiDataToSend[] = {0x91, 0x3c, 0x40};
    int             i;

    MIDIClientCreate(CFSTR("Magical MIDI"), NULL, NULL,
                     &theMidiClient);
    MIDISourceCreate(theMidiClient, CFSTR("Magical MIDI Source"),
                     &midiOut);
    MIDIOutputPortCreate(theMidiClient, CFSTR("Magical MIDI Out Port"),
                         &outPort);

    pkt = MIDIPacketListInit(pktList);
    pkt = MIDIPacketListAdd(pktList, 1024, pkt, 0, 3, midiDataToSend);

    for (i = 0; i < 100; i++) {
        if (pkt == NULL || MIDISend(outPort, midiOut, pktList)) {
            printf("failed to send the midi.\n");
        } else {
            printf("sent!\n");
        }
        sleep(1);
    }

return 0;
}

Answer 1

您正在调用MIDISourceCreate来创建虚拟MIDI源。

这意味着您的来源将出现在其他应用中。 MIDI设置用户界面，这些应用程序可以选择是否收听您的来源。您的MIDI不会被发送到任何物理MIDI端口，除非其他应用程序碰巧将其传送到那里。这也意味着你的应用程序无法选择发送的MIDI所在的位置。我假设你想要的是什么。

The documentation for MIDISourceCreate说：

创建虚拟源后，使用MIDIReceived将虚拟源中的MIDI消息传输到连接到虚拟源的任何客户端。

所以，做两件事：

删除创建输出端口的代码。你不需要它。
将MIDISend(outPort, midiOut, pktList)更改为：MIDIReceived(midiOut, pktlist)。

这应该可以解决你的问题。

那么输出端口有什么用呢？如果您想将MIDI数据导向特定目的地（可能是物理MIDI端口），则不会创建虚拟MIDI源。代替：

调用MIDIOutputPortCreate()制作输出端口
使用MIDIGetNumberOfDestinations()和MIDIGetDestination()获取目的地列表，找到您感兴趣的目的地。
要将MIDI发送到一个目的地，请拨打MIDISend(outputPort, destination, packetList)。

Answer 2

我只是留在这里供我自己参考。这是一个完整的例子100％基于你的，但包括另一方（接收），我的坏C代码和接受的答案的更正（当然）。

#import "AppDelegate.h"

@implementation AppDelegate

@synthesize window = _window;

#define NSLogError(c,str) do{if (c) NSLog(@"Error (%@): %u:%@", str, (unsigned int)c,[NSError errorWithDomain:NSMachErrorDomain code:c userInfo:nil]); }while(false)

static void spit(Byte* values, int length, BOOL useHex) {
    NSMutableString *thing = [@"" mutableCopy];
    for (int i=0; i<length; i++) {
        if (useHex)
            [thing appendFormat:@"0x%X ", values[i]];
        else
            [thing appendFormat:@"%d ", values[i]];
    }
    NSLog(@"Length=%d %@", length, thing);
}

- (void) startSending {
    MIDIEndpointRef midiOut;
    char pktBuffer[1024];
    MIDIPacketList* pktList = (MIDIPacketList*) pktBuffer;
    MIDIPacket     *pkt;
    Byte            midiDataToSend[] = {0x91, 0x3c, 0x40};
    int             i;

    MIDISourceCreate(theMidiClient, CFSTR("Magical MIDI Source"),
                     &midiOut);
    pkt = MIDIPacketListInit(pktList);
    pkt = MIDIPacketListAdd(pktList, 1024, pkt, 0, 3, midiDataToSend);

    for (i = 0; i < 100; i++) {
        if (pkt == NULL || MIDIReceived(midiOut, pktList)) {
            printf("failed to send the midi.\n");
        } else {
            printf("sent!\n");
        }
        sleep(1);
    }
}

void ReadProc(const MIDIPacketList *packetList, void *readProcRefCon, void *srcConnRefCon)
{
    const MIDIPacket *packet = &packetList->packet[0];

    for (int i = 0; i < packetList->numPackets; i++)
    {

        NSData *data = [NSData dataWithBytes:packet->data length:packet->length];
        spit((Byte*)data.bytes, data.length, YES);

        packet = MIDIPacketNext(packet);
    }
}

- (void) setupReceiver {
    OSStatus s;
    MIDIEndpointRef virtualInTemp;
    NSString *inName = [NSString stringWithFormat:@"Magical MIDI Destination"];
    s = MIDIDestinationCreate(theMidiClient, (__bridge CFStringRef)inName, ReadProc,  (__bridge void *)self, &virtualInTemp);
    NSLogError(s, @"Create virtual MIDI in");
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    MIDIClientCreate(CFSTR("Magical MIDI"), NULL, NULL,
                     &theMidiClient);
    [self setupReceiver];
    [self startSending];

}

@end

Answer 3

其他人正在跳过的一些细节：time 的MIDIPacketListAdd参数对某些音乐应用非常重要。

以下是如何检索它的示例：

#import <mach/mach_time.h>
MIDITimeStamp midiTime = mach_absolute_time();

来源：Apple Documentation

然后，应用于其他示例：

pktBuffer[1024];
MIDIPacketList *pktList = (MIDIPacketList*)pktBuffer;
MIDIPacket *pktPtr = MIDIPacketListInit(pktList);
MIDITimeStamp midiTime = mach_absolute_time();
Byte midiDataToSend[] = {0x91, 0x3c, 0x40};
pktPtr = MIDIPacketListAdd(pktList, sizeof(pktList), pktPtr, midiTime, midiDataToSend, sizeof(midiDataToSend));

Answer 4

请考虑您自己的Midi客户端创建应用程序可能崩溃，或者发送midi的主机也可能崩溃。您可以通过检查客户端/目标是否已经存在来解决此问题，然后通过处理单例分配来完成。当您的Midi客户端存在但无法正常工作时，这是因为您需要告诉CoreMidi您的服装制造的客户端能够处理什么，以及当发送主机的主机使用大量时间戳（又称为ableton和其他时间戳）时，它会有什么样的延迟。

在您的.h文件中

#import <CoreMIDI/CoreMIDI.h>
#import <CoreAudio/HostTime.h>

@interface YourVirtualMidiHandlerObject : NSObject 

@property (assign, nonatomic) MIDIClientRef midi_client;
@property (nonatomic) MIDIEndpointRef outSrc;
@property (nonatomic) MIDIEndpointRef inSrc;
- (id)initWithVirtualSourceName:(NSString *)clientName;

@end

在您的.m文件中

@interface YourVirtualMidiHandlerObject () {
   MIDITimeStamp midiTime;
   MIDIPacketList pktList;
}
@end

您将通过以下方式准备启动虚拟客户端也在您的.m文件中

@implementation YourVirtualMidiHandlerObject 

// this you can call in dealloc or manually 
// else where when you stop working with your virtual client
-(void)teardown {
    MIDIEndpointDispose(_inSrc);
    MIDIEndpointDispose(_outSrc);
    MIDIClientDispose(_midi_client);
}

- (id)initWithVirtualSourceName:(NSString *)clientName { 
    if (self = [super init]) {
        OSStatus status = MIDIClientCreate((__bridge CFStringRef)clientName, (MIDINotifyProc)MidiNotifyProc, (__bridge void *)(self), &_midi_client);

        BOOL isSourceLoaded = NO;
        BOOL isDestinationLoaded = NO;

        ItemCount sourceCount = MIDIGetNumberOfSources();
        for (ItemCount i = 0; i < sourceCount; ++i) {
            _outSrc = MIDIGetSource(i);
            if ( _outSrc != 0 ) {
                if ([[self getMidiDisplayName:_outSrc] isEqualToString:clientName] && !isSourceLoaded) {
                    isSourceLoaded = YES; 
                    break; //stop looping thru sources if it is existing
                }
            }
        }

        ItemCount destinationCount = MIDIGetNumberOfDestinations();
        for (ItemCount i = 0; i < destinationCount; ++i) {
            _inSrc = MIDIGetDestination(i);
            if (_inSrc != 0) {
                if ([[self getMidiDisplayName:_inSrc] isEqualToString:clientName] && !isDestinationLoaded) {
                    isDestinationLoaded = YES;
                    break; //stop looping thru destinations if it is existing
                }
            }
        }

        if(!isSourceLoaded) {
            //your costume source needs to tell CoreMidi what it is handling
            MIDISourceCreate(_midi_client, (__bridge CFStringRef)clientName, &_outSrc);
            MIDIObjectSetIntegerProperty(_outSrc, kMIDIPropertyMaxTransmitChannels, 16);
            MIDIObjectSetIntegerProperty(_outSrc, kMIDIPropertyTransmitsProgramChanges, 1);
            MIDIObjectSetIntegerProperty(_outSrc, kMIDIPropertyTransmitsNotes, 1);
            // MIDIObjectSetIntegerProperty(_outSrc, kMIDIPropertyTransmitsClock, 1);
            isSourceLoaded = YES;
        }

        if(!isDestinationLoaded) {
            //your costume destination needs to tell CoreMidi what it is handling
            MIDIDestinationCreate(_midi_client, (__bridge CFStringRef)clientName, midiRead, (__bridge void *)(self), &_inSrc);
            MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyAdvanceScheduleTimeMuSec, 1); // consider more 14ms in some cases
            MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyReceivesClock, 1);
            MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyReceivesNotes, 1);
            MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyReceivesProgramChanges, 1);
            MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyMaxReceiveChannels, 16);
            // MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyReceivesMTC, 1);
            // MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyReceivesBankSelectMSB, 1);
            // MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertyReceivesBankSelectLSB, 1);
            // MIDIObjectSetIntegerProperty(_inSrc, kMIDIPropertySupportsMMC, 1);
            isDestinationLoaded = YES;
        }

        if (!isDestinationLoaded || !isSourceLoaded) {
            if (status != noErr ) {
                NSLog(@"Failed creation of virtual Midi client \"%@\", so disposing the client!",clientName);
                MIDIClientDispose(_midi_client);
            }
        }
    }
    return self;
}

// Returns the display name of a given MIDIObjectRef as an NSString
-(NSString *)getMidiDisplayName:(MIDIObjectRef)obj {
    CFStringRef name = nil;
    if (noErr != MIDIObjectGetStringProperty(obj, kMIDIPropertyDisplayName, &name)) return nil;
    return (__bridge NSString *)name;
}

对于那些尝试读取速度（MIDI传输）并在创建过程中为虚拟目标设置属性的人来说... 别忘了时间戳是随数据包一起发送的，但是数据包可以包含几个相同类型的命令，甚至几个时钟命令。构建时钟计数器以查找bpm速度时，您必须在计算之前至少考虑对其中的12个进行计数。当您只使用其中的3个时，实际上是在测量自己的缓冲区读取处理延迟，而不是实际的时间戳。如果midi发件人无法使用...正确设置时间戳，则您的阅读过程（回调）将处理时间戳。

void midiRead(const MIDIPacketList * pktlist, void * readProcRefCon, void * srcConnRefCon) {

    const MIDIPacket *pkt = pktlist->packet;

    for ( int index = 0; index < pktlist->numPackets; index++, pkt = MIDIPacketNext(pkt) ) {
        MIDITimeStamp timestamp = pkt->timeStamp;
        if ( !timestamp ) timestamp = mach_absolute_time();
        if ( pkt->length == 0 ) continue;

        const Byte *p = &pkt->data[0];
        Byte functionalDataGroup = *p & 0xF0;

        // Analyse the buffered bytes in functional groups is faster
        // like 0xF will tell it is clock/transport midi stuff
        // go in detail after this will shorten the processing
        // and it is easier to read in code
        switch (functionalDataGroup) {
            case 0xF : {
                   // in here read the exact Clock command
                   // 0xF8 = clock
               }
               break;
            case ... : {
                   // do other nice grouped stuff here, like reading notes
               }
               break;
            default  : break;
        }
    }
}

不要忘记客户端需要一个用于处理内部通知的回调。

void MidiNotifyProc(const MIDINotification* message, void* refCon) {

    // when creation of virtual client fails we despose the whole client
    // meaning unless you need it you can ignore added/removed notifications
    if (message->messageID != kMIDIMsgObjectAdded &&
        message->messageID != kMIDIMsgObjectRemoved) return;

    // reactions to other midi notications you gonna trigger here..
}

然后您可以发送带有...的midi

-(void)sendMIDICC:(uint8_t)cc Value:(uint8_t)v ChZeroToFifteen:(uint8_t)ch {


    MIDIPacket *packet = MIDIPacketListInit(&pktList);
    midiTime = packet->timeStamp;

    unsigned char ctrl[3] = { 0xB0 + ch, cc, v };
    while (1) {
        packet = MIDIPacketListAdd(&pktList, sizeof(pktList), packet, midiTime, sizeof(ctrl), ctrl);
        if (packet != NULL) break;
        // create an extra packet to fill when it failed before
        packet = MIDIPacketListInit(&pktList);
    }

    // OSStatus check = // you dont need it if you don't check failing
    MIDIReceived(_outSrc, &pktList);
}

为什么这个简单的CoreMIDI程序不能产生MIDI输出？

4 个答案: