Java Reference
In-Depth Information
chunkCount = 0;
byte[] data = new byte[bytesPerChunk];
int bytesRead = 0;
while ((bytesRead =, 0, data.length)) != -1) {
baos.write(data, 0, bytesRead);
decodedAudio = new ByteArrayInputStream(baos.toByteArray());
DataLine.Info info = new DataLine.Info(SourceDataLine.class, decodedFormat);
line = (SourceDataLine) AudioSystem.getLine(info);;
audioConsumer = new AudioDataConsumer(bytesPerChunk, 10);
isPlaying = false;
thread = new Thread(new SoundRunnable());
} catch (Exception ex) {
throw new RuntimeException(ex);
In Listing 9-2 we can see that a SoundHelper class is created by calling a constructor and providing a
URL. If the provided URL starts with the word jar , we know we must copy the sound file out of the JAR
and into the local file system; the method createLocalFile is used to do this. Looking at the
implementation of createLocalFile , we can see that a suitable location is identified in a subdirectory
created in the user's home directory. If this file exists, then the code assumes that this file was copied
over during a previous run, and the URL to this file is returned. If the file did not exist, then the
createLocalFile method opens an input stream from the copy in the JAR and also opens an output
stream to the new file. The contents of the input stream are then written to the output stream, creating a
copy of the sound file on the local disk.
Once the class SoundHelper has a URL pointing to valid sound file, it is then time to decode the sound
file so we can play it. The method init uses the static method getAudioInputStream from the Java Sound
class AudioSystem . The AudioInputStream returned by getAudioInputStream may or may not be in a format
we want to work with. Since we are going to do some digital signal processing (DSP) on the contents of
this stream, we want to normalize the format so we only have to write one class for doing the DSP.
Using the original format of the AudioInputStream as stored in the variable baseFormat , a new
AudioFormat is created called decodedFormat . The variable decodedFormat is set to be PCM_SIGNED , which is
how our DSP code expects it to be formatted.
So, now that we know what format we want our audio data in, it is time to actually get the audio
data. The audio data will ultimately be stored as a byte array inside the variable decodedAudio . The
variable decodedAudio is a ByteArrayInputStream and provides a convenient API for working with a byte
array as a stream.
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