package cas.cs4tb3.mellowd;
import javax.sound.midi.*;The TimingEnvironment class handles timing information for a sequence. It allows for
conversion from a classical timing definition of a beat to a MIDI tick count. It is
also responsible for modifying the time signature and tempo of the sequence with the
creation of the appropriate MIDI meta messages. See
public class TimingEnvironment {The MIDI meta message identifier for a time signature message.
private static final byte TIME_SIGNATURE_MIDI_SUBTYPE = 0x58;The MIDI meta message identifier for a tempo message.
private static final byte TEMPO_MIDI_SUBTYPE = 0x51;The number of microseconds in each minute (60,000,000). This constant aids in calculating the microseconds per beat for a BPM conversion.
private static final int MICROSECONDS_PER_MINUTE = 60000000;This constant is the number of ticks that need to pass on the MIDI clock for the metronome to click. This clock is independent from the sequencer clock. Redefining the PPQN should not affect this clock. Therefore we will leave it at the standard 24 ticks per click.
private static final byte TICKS_PER_METER_CLICK = 24;This constant appears in the time signature midi message. 1⁄4 consists of 8 1⁄32. There should be no reason to change this.
private static final byte THIRTY_SECOND_NOTES_PER_QUARTER = 8;The PPQN is the Pulses Per Quarter Note. It is also referred to as simply PPQ.
It will be 960 by default for all sequences but reserve the right to change it
if we need a higher resolution. This is the number of clock ticks that pass over
the duration of a single quarter note.
private static final int DEFAULT_PPQN = 960;Store all of the timing information. The time signature is timeSigNum⁄timeSigDen. Our pluses per quarter note and our tempo.
private byte timeSigNum;
private byte timeSigDen;
private int ppqn;
private int bpm;The numerator and denominator for the time signature gives the synthesiser some hints on what are the down and up beats. The bpm is the tempo.
public TimingEnvironment(byte numerator, byte denominator, int bpm) {
this.timeSigNum = numerator;
this.timeSigDen = denominator;
this.ppqn = DEFAULT_PPQN;
this.bpm = bpm;
}
public Sequence createSequence() {
try {
Sequence s = new Sequence(Sequence.PPQ, ppqn);
Track timeDataTrack = s.createTrack();
timeDataTrack.add(new MidiEvent(this.timeSignatureMessage(), 0));
timeDataTrack.add(new MidiEvent(this.tempoMessage(), 0));
return s;
} catch (InvalidMidiDataException e) {
throw new RuntimeException(e);
}
}Get the number of ticks per quarter note. This is the resolution of the timing.
public int getPPQ() {
return ppqn;
}Get the tempo in beats per minute.
public int getTempo() {
return this.bpm;
}The PPQN was chosen as to support triplets on an integer number of
ticks but the resolution of other ratios will vary and some precision
may be lost when cast to a long.
public long ticksInBeat(Beat beat) {
return (long) (ppqn * beat.getNumQuarters());
}Create a MIDI message that can be sent to set the time signature of the sequence to this time signature.
public MetaMessage timeSignatureMessage() {
MetaMessage timeSigMessage = null;
try {
timeSigMessage = new MetaMessage(TIME_SIGNATURE_MIDI_SUBTYPE, new byte[] {
timeSigNum,
(byte) (Math.log(timeSigDen) / Math.log(2)),
TICKS_PER_METER_CLICK,
THIRTY_SECOND_NOTES_PER_QUARTER
}, 4);
} catch (InvalidMidiDataException ignored) {
/* Will never happen as the message type is a defined constant */
}
return timeSigMessage;
}Create a MIDI message that can be sent to set the tempo of the sequence to this tempo.
public MetaMessage tempoMessage() {
int microSecPerBeat = MICROSECONDS_PER_MINUTE / bpm;
MetaMessage tempoMessage = null;
try {
tempoMessage = new MetaMessage(TEMPO_MIDI_SUBTYPE, new byte[] {
(byte) ((microSecPerBeat >>> 16) & 0xFF),
(byte) ((microSecPerBeat >>> 8 ) & 0xFF),
(byte) ((microSecPerBeat ) & 0xFF)
}, 3);
} catch (InvalidMidiDataException ignored) {
/* Will never happen as the message type is a defined constant */
}
return tempoMessage;
}
}