Java tutorial
/* * Copyright (c) 2004 David Flanagan. All rights reserved. * This code is from the book Java Examples in a Nutshell, 3nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose, * including teaching and use in open-source projects. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book, * please visit http://www.davidflanagan.com/javaexamples3. */ import java.io.IOException; import java.net.URL; import javax.sound.midi.InvalidMidiDataException; import javax.sound.midi.MetaEventListener; import javax.sound.midi.MetaMessage; import javax.sound.midi.MidiSystem; import javax.sound.midi.MidiUnavailableException; import javax.sound.midi.Sequencer; import javax.sound.midi.Synthesizer; import javax.sound.sampled.AudioFormat; import javax.sound.sampled.AudioInputStream; import javax.sound.sampled.AudioSystem; import javax.sound.sampled.DataLine; import javax.sound.sampled.LineUnavailableException; import javax.sound.sampled.SourceDataLine; import javax.sound.sampled.UnsupportedAudioFileException; /** * This class plays sounds streaming from a URL: it does not have to preload the * entire sound into memory before playing it. It is a command-line application * with no gui. It includes code to convert ULAW and ALAW audio formats to PCM * so they can be played. Use the -m command-line option before MIDI files. */ public class Main { // Create a URL from the command-line argument and pass it to the // right static method depending on the presence of the -m (MIDI) option. public static void main(String[] args) throws Exception { if (args[0].equals("-m")) streamMidiSequence(new URL(args[1])); else streamSampledAudio(new URL(args[0])); // Exit explicitly. // This is needed because the audio system starts background threads. System.exit(0); } /** Read sampled audio data from the specified URL and play it */ public static void streamSampledAudio(URL url) throws IOException, UnsupportedAudioFileException, LineUnavailableException { AudioInputStream ain = null; // We read audio data from here SourceDataLine line = null; // And write it here. try { // Get an audio input stream from the URL ain = AudioSystem.getAudioInputStream(url); // Get information about the format of the stream AudioFormat format = ain.getFormat(); DataLine.Info info = new DataLine.Info(SourceDataLine.class, format); // If the format is not supported directly (i.e. if it is not PCM // encoded, then try to transcode it to PCM. if (!AudioSystem.isLineSupported(info)) { // This is the PCM format we want to transcode to. // The parameters here are audio format details that you // shouldn't need to understand for casual use. AudioFormat pcm = new AudioFormat(format.getSampleRate(), 16, format.getChannels(), true, false); // Get a wrapper stream around the input stream that does the // transcoding for us. ain = AudioSystem.getAudioInputStream(pcm, ain); // Update the format and info variables for the transcoded data format = ain.getFormat(); info = new DataLine.Info(SourceDataLine.class, format); } // Open the line through which we'll play the streaming audio. line = (SourceDataLine) AudioSystem.getLine(info); line.open(format); // Allocate a buffer for reading from the input stream and writing // to the line. Make it large enough to hold 4k audio frames. // Note that the SourceDataLine also has its own internal buffer. int framesize = format.getFrameSize(); byte[] buffer = new byte[4 * 1024 * framesize]; // the buffer int numbytes = 0; // how many bytes // We haven't started the line yet. boolean started = false; for (;;) { // We'll exit the loop when we reach the end of stream // First, read some bytes from the input stream. int bytesread = ain.read(buffer, numbytes, buffer.length - numbytes); // If there were no more bytes to read, we're done. if (bytesread == -1) break; numbytes += bytesread; // Now that we've got some audio data, to write to the line, // start the line, so it will play that data as we write it. if (!started) { line.start(); started = true; } // We must write bytes to the line in an integer multiple of // the framesize. So figure out how many bytes we'll write. int bytestowrite = (numbytes / framesize) * framesize; // Now write the bytes. The line will buffer them and play // them. This call will block until all bytes are written. line.write(buffer, 0, bytestowrite); // If we didn't have an integer multiple of the frame size, // then copy the remaining bytes to the start of the buffer. int remaining = numbytes - bytestowrite; if (remaining > 0) System.arraycopy(buffer, bytestowrite, buffer, 0, remaining); numbytes = remaining; } // Now block until all buffered sound finishes playing. line.drain(); } finally { // Always relinquish the resources we use if (line != null) line.close(); if (ain != null) ain.close(); } } // A MIDI protocol constant that isn't defined by javax.sound.midi public static final int END_OF_TRACK = 47; /* MIDI or RMF data from the specified URL and play it */ public static void streamMidiSequence(URL url) throws IOException, InvalidMidiDataException, MidiUnavailableException { Sequencer sequencer = null; // Converts a Sequence to MIDI events Synthesizer synthesizer = null; // Plays notes in response to MIDI events try { // Create, open, and connect a Sequencer and Synthesizer // They are closed in the finally block at the end of this method. sequencer = MidiSystem.getSequencer(); sequencer.open(); synthesizer = MidiSystem.getSynthesizer(); synthesizer.open(); sequencer.getTransmitter().setReceiver(synthesizer.getReceiver()); // Specify the InputStream to stream the sequence from sequencer.setSequence(url.openStream()); // This is an arbitrary object used with wait and notify to // prevent the method from returning before the music finishes final Object lock = new Object(); // Register a listener to make the method exit when the stream is // done. See Object.wait() and Object.notify() sequencer.addMetaEventListener(new MetaEventListener() { public void meta(MetaMessage e) { if (e.getType() == END_OF_TRACK) { synchronized (lock) { lock.notify(); } } } }); // Start playing the music sequencer.start(); // Now block until the listener above notifies us that we're done. synchronized (lock) { while (sequencer.isRunning()) { try { lock.wait(); } catch (InterruptedException e) { } } } } finally { // Always relinquish the sequencer, so others can use it. if (sequencer != null) sequencer.close(); if (synthesizer != null) synthesizer.close(); } } }