ios - 获取使用 Logic 生成的 midi 序列 (MusicSequence) 标记

Question

我正在开发一款应用程序，该应用程序使用音频单元播放 MIDI 序列 (.mid)。 midi 文件是使用 Logic 创建的，它提供了在时间轴上添加标记的可能性。

在代码中，我使用 MusicSequence MusicPlayer 读取文件，使用 MIDIClientCreate MIDIDestinationCreate 解析 MIDI 数据包。

主要方法

    OSStatus result = noErr;


// Initialise the music sequence
NewMusicSequence(&_s);

// Get a string to the path of the MIDI file which
// should be located in the Resources folder
NSString *midiFilePath = [[NSBundle mainBundle]
                          pathForResource:@"mymidifile"
                          ofType:@"mid"];

// Create a new URL which points to the MIDI file
NSURL * midiFileURL = [NSURL fileURLWithPath:midiFilePath];

// Load the file
MusicSequenceFileLoad(_s, (__bridge CFURLRef) midiFileURL, 0, 0);



// Initialise the music player
NewMusicPlayer(&_p);


// Load the sound from EXS file
[self loadFromEXS:@"Grand Piano" withSampler:_samplerUnit];

//Load Click
[self loadFromSoundFont:@"hit set" withSampler:_samplerUnit2];


//Assign channel to tracks
MusicTrack track = NULL;
MusicTrack track2 = NULL;
MusicSequenceGetIndTrack(_s, 1, &track);
MusicSequenceGetIndTrack(_s, 2, &track2);

//Assign tracks to audio units
MusicTrackSetDestNode(track, _samplerNode);
MusicTrackSetDestNode(track2, _samplerNode2);


// Create a client
result = MIDIClientCreate(CFSTR("Virtual Client"),MyMIDINotifyProc,(__bridge void *)(self),&_virtualMidi);
NSAssert( result == noErr, @"MIDIClientCreate failed. Error code: %d '%.4s'", (int) result, (const char *)&result);


// Create an endpoint
result = MIDIDestinationCreate(_virtualMidi, (CFStringRef)@"Virtual Destination", MyMIDIReadProc, (__bridge void *)(self), &_virtualEndPoint);

NSAssert( result == noErr, @"MIDIDestinationCreate failed. Error code: %d '%.4s'", (int) result, (const char *)&result);


// ************* Set the endpoint of the sequence to be our virtual endpoint
MusicSequenceSetMIDIEndpoint(_s, _virtualEndPoint);




// Load the sequence into the music player
MusicPlayerSetSequence(_p, _s);
// Called to do some MusicPlayer setup. This just
// reduces latency when MusicPlayerStart is called
MusicPlayerPreroll(_p);
// Starts the music playing
MusicPlayerStart(_p);

还有我的 readProc 函数

void MyMIDIReadProc(const MIDIPacketList *pktlist,
                AudioProcessor *refCon,
                void *connRefCon) {


AudioUnit *player = nil;

MIDIPacket *packet = (MIDIPacket *)pktlist->packet;
NSString *messageType;

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


    Byte midiStatus = packet->data[0];
    Byte midiCommand = midiStatus >> 4;// mask off all but top 4 bits
    Byte note = packet->data[1] & 0x7F;
    Byte velocity = packet->data[2] & 0x7F;

    // find the channel by masking off all but the low 4 bits
    NSInteger midiChannel = midiStatus & 0x0F;


    switch (midiStatus & 0xF0) {
        case 0x80:
            messageType = @"Note Off";
            break;

        case 0x90:
            messageType = @"Note On";
            break;

        case 0xA0:
            messageType = @"Aftertouch";
            break;

        case 0xB0:
            messageType = @"Control change";
            break;

        case 0xC0:
            messageType = @"Program Change";
            break;

        case 0xD0:
            messageType = @"Channel Pressure";
            break;

        case 0xE0:
            messageType = @"Pitch Wheel";
            break;

        default:
            messageType = @"Unk";
            break;
    }
    NSLog(@"%@",messageType);
    int noteNumber = ((int) note) % 12;
    NSString *noteType;
    switch (noteNumber) {
        case 0:
            noteType = @"C";
            break;
        case 1:
            noteType = @"C#/Db";
            break;
        case 2:
            noteType = @"D";
            break;
        case 3:
            noteType = @"D#/Eb";
            break;
        case 4:
            noteType = @"E";
            break;
        case 5:
            noteType = @"F";
            break;
        case 6:
            noteType = @"F#/Gb";
            break;
        case 7:
            noteType = @"G";
            break;
        case 8:
            noteType = @"G#/Ab";
            break;
        case 9:
            noteType = @"A";
            break;
        case 10:
            noteType = @"A#/Bb";
            break;
        case 11:
            noteType = @"B";
            break;
        default:
            break;
    }




    if( velocity == 0 ){

        UInt32 noteOff =    kMIDIMessage_NoteOff << 4 | 0;
        if( midiChannel == 0 ){
            MusicDeviceMIDIEvent (refCon.samplerUnit, noteOff, note, 0, 0);
        }else if( midiChannel == 1 ){
            MusicDeviceMIDIEvent (refCon.samplerUnit2, noteOff, note, 0, 0);
        }

    }else{

        if( midiChannel == 0 ){
            MusicDeviceMIDIEvent (refCon.samplerUnit, midiStatus, note, velocity, 0);
        }else if( midiChannel == 1 ){
            MusicDeviceMIDIEvent (refCon.samplerUnit2, midiStatus, note, velocity, 0);
        }

    }

    packet = MIDIPacketNext(packet);
}

通过我的 readProc 函数，我可以看到所有的 MIDI 消息，但看不到标记...

如果我在 Logic 中重新打开 midi 文件，标记在文件中，但是在哪里...我如何在代码中获取它？

Answer 1

标记作为标记元事件包含在 MIDI 文件中。所以你需要扩展你的解析来支持元事件。元事件的状态为 0xFF。对于标记，下一个字节是 0x06，然后是长度和字符数。