ios - 如何知道 midi 回调中的循环结束

Question

我有一个 midi 文件循环(带有 MusicPlayer )并遵循回调过程

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

AudioUnit *player = (AudioUnit*) refCon;

const MIDIPacket *packet = &pktlist->packet[0];

for (int i=0; i < pktlist->numPackets; i++) {
    Byte midiStatus = packet->data[0];
    Byte midiCommand = midiStatus >> 4;

    NSMutableString *hex = [NSMutableString stringWithCapacity:10];
    for (int i=0; i < 10; i++) {
        [hex appendFormat:@"%02x ", packet->data[i]];

    }
    NSLog(hex);

    if (midiCommand == 0x09) {
        Byte note = packet->data[1] & 0x7F;
        Byte velocity = packet->data[2] & 0x7F;
        OSStatus result = noErr;
        result = MusicDeviceMIDIEvent (player, midiStatus, note, velocity, 0);

    }
    packet = MIDIPacketNext(packet);
}
}

NSLog(hex)只会显示以 90(注意)、b0( Controller )、e0(弯音)或 c0(程序更改)开头的数据包。那么回调函数是否根本没有得到轨道结束标记 - FF 2F 00 - 或者我在这里遗漏了什么？我想在每次循环重新开始时得到通知。

这就是我注册回调的方式:

MIDIClientRef virtualMidi;
result = MIDIClientCreate(CFSTR("Virtual Client"),
                          MyMIDINotifyProc,
                          NULL,
                          &virtualMidi);

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

// Create an endpoint
MIDIEndpointRef virtualEndpoint;
result = MIDIDestinationCreate(virtualMidi, @"Virtual Destination", MyMIDIReadProc, self.samplerUnit, &virtualEndpoint);

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

MusicSequenceSetMIDIEndpoint(s, virtualEndpoint);

Answer 1

End Of Track Marker 是一个永远不会发送到 MIDI 设备的 Midi 元消息；它只存在于 MIDI 文件中。

更新:

您可以使用用户事件在轨道循环播放时获得通知。

为用户事件添加回调:

static void sequenceUserCallback(void *inClientData,
                                 MusicSequence             inSequence,
                                 MusicTrack                inTrack,
                                 MusicTimeStamp            inEventTime,
                                 const MusicEventUserData *inEventData,
                                 MusicTimeStamp            inStartSliceBeat,
                                 MusicTimeStamp            inEndSliceBeat)
{
  NSLog(@"track was looped");
}

并创建一个这样的用户事件:

static MusicEventUserData userData = {1, 0x01 /* anything you want*/ };

MusicTrack musicTrack;
MusicSequenceGetIndTrack(sequence, 0 /* your track index of interest */, &musicTrack);

/* timestamp 0 should be fine if you always loop from the beginning;
   alternatively add the event at end of track */
MusicTrackNewUserEvent(musicTrack, 0 /* timestamp */ , &userData);