Swing Hacks

390

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Chapter 10, Audio

#76 Play Non-Trivial Audio

HACK

Notice in the constructor that, as with the Clip, the way to get an actual

Line object is to construct a DataLine.Info object and then pass that to

AudioSystem

. This time, you construct a

DataLine.Info

class with both the

SourceDataLine

class—you need this subclass of

Line

because it provides the

write( )

method with which you supply bytes to the

Line

—and an

AudioFormat

object describing the data you’ll be supplying. Assuming that

doesn’t throw a

LineUnavailableException (and it shouldn’t, because the

format is already known to be PCM, which JavaSound always supports),

you’ll have a line that you can open and start writing bytes to.

As mentioned previously, the key issue for the thread that reads bytes from

the file and writes them to the

Line is that it has to be aware of frame bound-

aries. In this code,

readPoint indicates the index of the buffer to start read-

ing bytes into. When you have an incomplete frame after reading from the

input stream, you copy the bytes from the incomplete frame to the front of

the buffer in preparation for the next read. For example, if you have a frame

size of 4, and

bytesRead % 4 equals 3, then you copy those 3 bytes to the front

of the buffer and set

readPoint to 3. The next read( ) will start at 3, and the

first byte read into the buffer will complete the frame from the previous

read( ).

Big Files, Big Sound

Since this is still in the realm of JavaSound, much of what was shown in the

Clip-based hack still works. A demo application simply has to provide

PCMFilePlayer with a file and then start it. Since PCMFilePlayer exposes its

Line through a get method, you can even wire up as a LineListener and get

notified of

STOP, START, OPEN, and CLOSE LineEvents. Example 10-9 shows the

simple GUI, using

PCMFilePlayer.

Example 10-9. Playing arbitrarily long uncompressed WAV or AIFF audio

import javax.sound.sampled.*;

public class StreamingLineSound extends Object

implements LineListener {

File soundFile;

JDialog playingDialog;

PCMFilePlayer player;

public static void main (String[] args) {

JFileChooser chooser = new JFileChooser( );

chooser.showOpenDialog(null);

File f = chooser.getSelectedFile( );

Play Non-Trivial Audio #76

Chapter 10, Audio

|

391

HACK

When run, this class shows a dialog box (seen in Figure 10-7), identical to

the one produced in “Play a Sound with JavaSound”

[Hack #71]. The only dif-

ference is that this one can stay up potentially indefinitely, since the player

can keep reading and writing bytes forever.

try {

StreamingLineSound s = new StreamingLineSound (f);

} catch (Exception e) {

e.printStackTrace( );

}

}

public StreamingLineSound (File f)

throws LineUnavailableException, IOException,

UnsupportedAudioFileException {

soundFile = f;

// prepare a dialog to display while playing

JOptionPane pane = new JOptionPane ("Playing " + f.getName( ),

JOptionPane.PLAIN_MESSAGE);

playingDialog = pane.createDialog (null, "Streaming Sound");

playingDialog.pack( );

player = new PCMFilePlayer (soundFile);

player.getLine( ).addLineListener (this);

player.start( );

}

// LineListener

public void update (LineEvent le) {

LineEvent.Type type = le.getType( );

if (type == LineEvent.Type.OPEN) {

System.out.println ("OPEN");

} else if (type == LineEvent.Type.CLOSE) {

System.out.println ("CLOSE");

System.exit (0);

} else if (type == LineEvent.Type.START) {

System.out.println ("START");

playingDialog.setVisible(true);

} else if (type == LineEvent.Type.STOP) {

System.out.println ("STOP");

playingDialog.setVisible(false);

player.line.close( );

}

}

}

Example 10-9. Playing arbitrarily long uncompressed WAV or AIFF audio (continued)