QuickTime for Java: A Developer's Notebook

Playing an Audio File from the Command Line

To finish this chapter, we’ll look at a very simple example of QTJ code that actually plays some media. To keep things simple, I’ll completely ignore the GUI, so all this will do is take a file path from the command line—presumably an MP3 or other audio file—and play it in QTJ.

How do I do that?

Compile and run the source for TrivialAudioPlayer.java, shown in Example 1-5.

Example 1-5. Playing an audio file from the command line

package com.oreilly.qtjnotebook.ch01;
  
import quicktime.*;
import quicktime.app.time.*;
import quicktime.io.*;
import quicktime.std.*;
import quicktime.std.movies.*;
 
import java.io.*;
  
public class TrivialAudioPlayer {
 
  public static void main (String[  ] args) {
      if (args.length != 1) {
          System.out.println (
              "Usage: TrivialAudioPlayer <file>");
          return;
      }
      try {
          QTSessionCheck.check( );
          QTFile f = new QTFile (new File(args[0]));
          OpenMovieFile omf = OpenMovieFile.asRead(f);
          Movie movie = Movie.fromFile (omf);
          TaskAllMovies.addMovieAndStart( );
          movie.start( );
      } catch (QTException e) {
          e.printStackTrace( );
      }
  }
}

Once compiled, run it with the path to an audio file as a command-line argument. Note that if you downloaded the book examples and compiled with the ant buildfile, the classes will be in the classes directory, so you’ll need to extend your classpath into there:

cadamson% java -classpath classes
  com.oreilly.qtjnotebook.ch01.TrivialAudioPlayer
  ~/mp3testing/Breakaway.mp3

What just happened?

This application provides a bare-bones load-and-play example. After checking that there’s a valid argument, it does the QTSessionCheck from the previous task to set up the QuickTime session.

Note

Any dynamic content in QuickTime is going to be a “movie,” even if it’s an audio-only file, like an MP3. This program also works for AACs, WAVs, iTunes Music Store songs, and anything else QuickTime can open.

The interesting part is in converting the argument to a java.io.File, then to a quicktime.io.OpenMovieFile, from which we can create a quicktime.std.Movie, which represents any kind of playable QuickTime content, in this case our audio file.

The start( ) method begins playing the movie, so once the program is running, you’ll hear your MP3 over your speakers or headphones. This program doesn’t provide a way to stop playback, so when you want to end the program, you’ll need to type ctrl-c, use the Windows Task Manager, or hit the Quit menu item that’s provided on Mac OS X.

What about...

Note

There’s more information on taksing in the next chapter.

...that weird TaskAllMovies call? This is required because our program doesn’t have a GUI, which ordinarily gives QTJ some cycles for decoding and playing the audio. Most of the programs in this book have on-screen GUIs, so they don’t need to do this.