如何在 Java 中实现 Midi 合成器

Question

Hy，我想在Java中实现一个Midi Synthesizer。（合成器 = 代表一个或多个乐器的新设备）

我实现的是一个javax.sound.midi.Receiver：

package at.bachmann.se.midi.smc;
import javax.sound.midi.MetaMessage;
import javax.sound.midi.MidiEvent;
import javax.sound.midi.MidiMessage;
import javax.sound.midi.Receiver;
import javax.sound.midi.ShortMessage;
import javax.sound.midi.SysexMessage;
public class SmcReceiver implements Receiver {
    public static final int NOTE_ON = 0x90;
    public static final int NOTE_OFF = 0x80;
    public static final String[] NOTE_NAMES = {"C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"};
    @Override
    public void close() {
        System.out.println();
    }
    @Override
    public void send(MidiMessage message, long timeStamp) {
        if(message instanceof ShortMessage) {
            ShortMessage sMessage = (ShortMessage) message;
            System.out.print("Channel: " + sMessage.getChannel() + " ");
            int cmd = sMessage.getCommand();
            int key = sMessage.getData1();
            int octave = (key / 12)-1;
            int note = key % 12;
            String noteName = NOTE_NAMES[note];
            int velocity = sMessage.getData2();
            switch(cmd) {
                case NOTE_ON:
                    System.out.println("Note on, " + noteName + octave + " key=" + key + " velocity: " + velocity);
                    break;
                case NOTE_OFF:
                    System.out.println("Note off, " + noteName + octave + " key=" + key + " velocity: " + velocity);
                    break;
            }
        } else if(message instanceof MetaMessage) {
            ;//TODO
        } else if(message instanceof SysexMessage) {
            ;//TODO
        }
    }
}

以下是使用默认值播放 midi 文件的方式：

public class MidiPlayerTest {
    @Test
    public void playMidiTst() throws InvalidMidiDataException, IOException, MidiUnavailableException {
        Sequencer sequencer = MidiSystem.getSequencer();
        System.out.println(sequencer.getClass().getName());
        sequencer.open();
        sequencer.setSequence(MidiSystem.getSequence(new File("tst.midi")));

        sequencer.start();
        while(true) {
            if(sequencer.isRunning()) {
                try {
                    Thread.sleep(200); // Check every second
                } catch(InterruptedException ignore) {
                    break;
                }
            } else {
                break;
            }
        }
        System.out.println("DONE!");
    }
}

所以我的问题是如何告诉音序器使用我的接收器？

我尝试/发现的事情：

• 我发现没有办法告诉音序器使用我的接收器。
• 我发现 javax.sound.midi.Synthesizer 使用了接收器，但我发现没有办法将自定义合成器类附加到音序器。

Answer 1

我的一个朋友给我发了我找不到的文档：S：https://docs.oracle.com/javase/tutorial/sound/MIDI-messages.html

所以这是工作代码：

public class MidiPlayerTest {
    @Test
    public void playMidiTst() throws InvalidMidiDataException, IOException, MidiUnavailableException {
        Sequencer sequencer = MidiSystem.getSequencer();
        Transmitter transmitter = sequencer.getTransmitter();
        transmitter.setReceiver(new SmcReceiver());
        System.out.println(sequencer.getClass().getName());
        sequencer.open();
        sequencer.setSequence(MidiSystem.getSequence(new File("tst.midi")));

        sequencer.start();
        while(true) {
            if(sequencer.isRunning()) {
                try {
                    Thread.sleep(200); // Check every second
                } catch(InterruptedException ignore) {
                    break;
                }
            } else {
                break;
            }
        }
        System.out.println("DONE!");
    }
}