/** Parse the given Midi file, and return an instance of this MidiFile
* class. After reading the midi file, this object will contain:
* - The raw list of midi events
* - The Time Signature of the song
* - All the tracks in the song which contain notes.
* - The number, starttime, and duration of each note.
*/
public void parse(MidiFileReader file, string filename)
{
string id;
int len;
this.filename = filename;
tracks = new List<MidiTrack>();
trackPerChannel = false;
id = file.ReadAscii(4);
if (id != "MThd") {
throw new MidiFileException("Doesn't start with MThd", 0);
}
len = file.ReadInt();
if (len != 6) {
throw new MidiFileException("Bad MThd header", 4);
}
trackmode = file.ReadShort();
int num_tracks = file.ReadShort();
quarternote = file.ReadShort();
events = new List<MidiEvent>[num_tracks];
for (int tracknum = 0; tracknum < num_tracks; tracknum++) {
events[tracknum] = ReadTrack(file);
MidiTrack track = new MidiTrack(events[tracknum], tracknum);
if (track.Notes.Count > 0) {
tracks.Add(track);
}
}
/* Get the length of the song in pulses */
foreach (MidiTrack track in tracks) {
MidiNote last = track.Notes[track.Notes.Count-1];
if (this.totalpulses < last.StartTime + last.Duration) {
this.totalpulses = last.StartTime + last.Duration;
}
}
/* If we only have one track with multiple channels, then treat
* each channel as a separate track.
*/
if (tracks.Count == 1 && HasMultipleChannels(tracks[0])) {
tracks = SplitChannels(tracks[0], events[tracks[0].Number]);
trackPerChannel = true;
}
CheckStartTimes(tracks);
/* Determine the time signature */
int tempo = 0;
int numer = 0;
int denom = 0;
foreach (List<MidiEvent> list in events) {
foreach (MidiEvent mevent in list) {
if (mevent.Metaevent == MetaEventTempo && tempo == 0) {
tempo = mevent.Tempo;
}
if (mevent.Metaevent == MetaEventTimeSignature && numer == 0) {
numer = mevent.Numerator;
denom = mevent.Denominator;
}
}
}
if (tempo == 0) {
tempo = 500000; /* 500,000 microseconds = 0.05 sec */
}
if (numer == 0) {
numer = 4; denom = 4;
}
timesig = new TimeSignature(numer, denom, quarternote, tempo);
}
/** Parse a single Midi track into a list of MidiEvents.
* Entering this function, the file offset should be at the start of
* the MTrk header. Upon exiting, the file offset should be at the
* start of the next MTrk header.
*/
private List<MidiEvent> ReadTrack(MidiFileReader file)
{
List<MidiEvent> result = new List<MidiEvent>(20);
int starttime = 0;
string id = file.ReadAscii(4);
if (id != "MTrk") {
throw new MidiFileException("Bad MTrk header", file.GetOffset() - 4);
}
int tracklen = file.ReadInt();
int trackend = tracklen + file.GetOffset();
int eventflag = 0;
while (file.GetOffset() < trackend) {
// If the midi file is truncated here, we can still recover.
// Just return what we've parsed so far.
int startoffset, deltatime;
byte peekevent;
try {
startoffset = file.GetOffset();
deltatime = file.ReadVarlen();
starttime += deltatime;
peekevent = file.Peek();
}
catch (MidiFileException e) {
return result;
}
MidiEvent mevent = new MidiEvent();
result.Add(mevent);
mevent.DeltaTime = deltatime;
mevent.StartTime = starttime;
if (peekevent >= EventNoteOff) {
mevent.HasEventflag = true;
eventflag = file.ReadByte();
}
// Console.WriteLine("offset {0}: event {1} {2} start {3} delta {4}",
// startoffset, eventflag, EventName(eventflag),
// starttime, mevent.DeltaTime);
if (eventflag >= EventNoteOn && eventflag < EventNoteOn + 16) {
mevent.EventFlag = EventNoteOn;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventNoteOn);
mevent.Notenumber = file.ReadByte();
mevent.Velocity = file.ReadByte();
}
else if (eventflag >= EventNoteOff && eventflag < EventNoteOff + 16) {
mevent.EventFlag = EventNoteOff;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventNoteOff);
mevent.Notenumber = file.ReadByte();
mevent.Velocity = file.ReadByte();
}
else if (eventflag >= EventKeyPressure &&
eventflag < EventKeyPressure + 16) {
mevent.EventFlag = EventKeyPressure;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventKeyPressure);
mevent.Notenumber = file.ReadByte();
mevent.KeyPressure = file.ReadByte();
}
else if (eventflag >= EventControlChange &&
eventflag < EventControlChange + 16) {
mevent.EventFlag = EventControlChange;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventControlChange);
mevent.ControlNum = file.ReadByte();
mevent.ControlValue = file.ReadByte();
}
else if (eventflag >= EventProgramChange &&
eventflag < EventProgramChange + 16) {
mevent.EventFlag = EventProgramChange;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventProgramChange);
mevent.Instrument = file.ReadByte();
}
else if (eventflag >= EventChannelPressure &&
eventflag < EventChannelPressure + 16) {
mevent.EventFlag = EventChannelPressure;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventChannelPressure);
mevent.ChanPressure = file.ReadByte();
}
else if (eventflag >= EventPitchBend &&
eventflag < EventPitchBend + 16) {
mevent.EventFlag = EventPitchBend;
mevent.Type = MessageType.Channel;
mevent.Channel = (byte)(eventflag - EventPitchBend);
mevent.PitchBend = file.ReadShort();
}
else if (eventflag == SysexEvent1) {
mevent.EventFlag = SysexEvent1;
mevent.Type = MessageType.SystemExclusive;
mevent.Metalength = file.ReadVarlen();
mevent.Value = file.ReadBytes(mevent.Metalength);
}
else if (eventflag == SysexEvent2) {
mevent.EventFlag = SysexEvent2;
mevent.Type = MessageType.SystemExclusive;
mevent.Metalength = file.ReadVarlen();
mevent.Value = file.ReadBytes(mevent.Metalength);
}
else if (eventflag == MetaEvent) {
mevent.EventFlag = MetaEvent;
mevent.Type = MessageType.Meta;
mevent.Metaevent = file.ReadByte();
mevent.Metalength = file.ReadVarlen();
mevent.Value = file.ReadBytes(mevent.Metalength);
if (mevent.Metaevent == MetaEventTimeSignature) {
if (mevent.Metalength < 2) {
// throw new MidiFileException(
// "Meta Event Time Signature len == " + mevent.Metalength +
// " != 4", file.GetOffset());
mevent.Numerator = (byte)0;
mevent.Denominator = (byte)4;
}
else if (mevent.Metalength >= 2 && mevent.Metalength < 4) {
mevent.Numerator = (byte)mevent.Value[0];
mevent.Denominator = (byte)System.Math.Pow(2, mevent.Value[1]);
}
else {
mevent.Numerator = (byte)mevent.Value[0];
mevent.Denominator = (byte)System.Math.Pow(2, mevent.Value[1]);
}
}
else if (mevent.Metaevent == MetaEventTempo) {
if (mevent.Metalength != 3) {
throw new MidiFileException(
"Meta Event Tempo len == " + mevent.Metalength +
" != 3", file.GetOffset());
}
mevent.Tempo = ( (mevent.Value[0] << 16) | (mevent.Value[1] << 8) | mevent.Value[2]);
}
else if (mevent.Metaevent == MetaEventEndOfTrack) {
/* break; */
}
}
else {
throw new MidiFileException("Unknown event " + mevent.EventFlag,
file.GetOffset()-1);
}
}
return result;
}