bool MidiParser::parseTrack(MidiEventList &midiEventList) {
char header[8];
forever {
if (!readFile(header, 8)) return false;
if (memcmp(header, trackID, 4) == 0) {
break;
} else {
qDebug() << "MidiParser: Wrong MIDI track signature, skipping unknown data chunk";
quint32 dataLen = qFromBigEndian<quint32>((uchar *)&header[4]);
if (file.seek(file.pos() + dataLen)) {
qDebug() << "MidiParser: Error in data chunk";
return false;
}
}
}
quint32 trackLen = qFromBigEndian<quint32>((uchar *)&header[4]);
char *trackData = new char[trackLen];
if (!readFile(trackData, trackLen)) {
delete trackData;
return false;
}
// Reserve memory for MIDI events, approx. 3 bytes per event
midiEventList.reserve(trackLen / 3);
qDebug() << "MidiParser: Memory reservation" << trackLen / 3;
// Parsing actual MIDI events
unsigned int runningStatus = 0;
uchar *data = (uchar *)trackData;
uchar sysexBuffer[MAX_SYSEX_LENGTH];
while(data < (uchar *)trackData + trackLen) {
SynthTimestamp time = parseVarLenInt(data);
quint32 message = 0;
if (*data & 0x80) {
// It's normal status byte
if ((*data & 0xF0) == 0xF0) {
// It's a special event
if (*data == 0xF0) {
// It's a sysex event
sysexBuffer[0] = *(data++);
quint32 sysexLength = parseVarLenInt(data);
if (MAX_SYSEX_LENGTH <= sysexLength) {
qDebug() << "MidiParser: too long sysex encountered:" << sysexLength;
data += sysexLength;
continue;
}
memcpy(&sysexBuffer[1], data, sysexLength);
data += sysexLength;
midiEventList.newMidiEvent().assignSysex(time, sysexBuffer, sysexLength + 1);
continue;
} else if (*data == 0xF7) {
qDebug() << "MidiParser: Fragmented sysex, unsupported";
data++;
quint32 len = parseVarLenInt(data);
data += len;
} else if (*(data++) == 0xFF) {
uint metaType = *(data++);
quint32 len = parseVarLenInt(data);
if (metaType == 0x2F) {
qDebug() << "MidiParser: End-of-track Meta-event";
runningStatus = 0x2F;
break;
} else if (metaType == 0x51) {
uint newTempo = qFromBigEndian<quint32>(data) >> 8;
midiEventList.newMidiEvent().assignSetTempoMessage(time, newTempo);
qDebug() << "MidiParser: Meta-event: Set tempo:" << newTempo;
data += len;
continue;
} else {
qDebug() << "MidiParser: Meta-event code" << metaType << "unsupported";
}
data += len;
} else {
qDebug() << "MidiParser: Unsupported event" << *(data++);
}
if (time > 0) {
// The event is unsupported. Nevertheless, assign a special marker event to retain timing information
qDebug() << "MidiParser: Adding sync event for" << time << "divisions";
midiEventList.newMidiEvent().assignSyncMessage(time);
}
continue;
} else if ((*data & 0xE0) == 0xC0) {
// It's a short message with one data byte
message = qFromLittleEndian<quint16>(data);
data += 2;
} else {
// It's a short message with two data bytes
message = qFromLittleEndian<quint32>(data) & 0xFFFFFF;
data += 3;
}
runningStatus = message & 0xFF;
} else {
// Handle running status
if ((runningStatus & 0x80) == 0) {
qDebug() << "MidiParser: First MIDI event must has status byte";
data++;
continue;
}
if ((runningStatus & 0xE0) == 0xC0) {
// It's a short message with one data byte
message = runningStatus | ((quint32)*data << 8);
data++;
} else {
// It's a short message with two data bytes
message = runningStatus | ((quint32)qFromLittleEndian<quint16>(data) << 8);
data += 2;
}
}
midiEventList.newMidiEvent().assignShortMessage(time, message);
}
if (runningStatus != 0x2F) {
qDebug() << "MidiParser: End-of-track Meta-event isn't the last event, file is probably corrupted.";
}
delete trackData;
qDebug() << "MidiParser: Parsed" << midiEventList.count() << "MIDI events";
return true;
}
