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A Complete Java Sound API Application

Figure 2 illustrates one of the sample applications that comes bundled with the Java Sound API demo. To run this program yourself, just download the associated files.

Then, run the following command from the download folder:

>java -jar JavaSoundDemo.jar

This command should produce the main application window illustrated in Figure 2.

Figure 2

Figure 2 The sample Java Sound application

Once you see the window in Figure 2, you can start to interact with the application. The application has four configured modes as indicated by the tab controls at the top of the window. The startup mode is Juke Box. On the left hand side of the window underneath the tabs is a list of sound files in different formats. Clicking the Start button plays back the contents of the listed files. Using the slider controls at the bottom of the window, you can modify the pan and gain settings for these pre-recorded sounds.

In using the Juke Box mode, you can get to play around with the playback features and sound formats of the Java Sound API. You might say the Juke Box mode is a kind of 21st-century "Hello World"!

So, what about recording audio? Clicking the second tab (Capture/Playback) at the top of Figure 2 moves the application into the mode illustrated in Figure 3. As mentioned earlier, this looks extremely complicated, but it's not really. The contents of Figure 3 represent a useful learning opportunity, so let's break it down into manageable chunks.

Figure 3

Figure 3 The Capture/Playback window

The box with the black background is called a sampling panel. This panel contains a graphical representation of the sound sample. When you play a sound, the sampling panel in Figure 3 provides visual feedback in the form of a vertical bar that moves from left to right. You can use the buttons above the sampling panel to control the playback as well as the recording. The buttons provide four options: Play (simple enough, just play a recording), Record (acquire a sound source and record it to memory), Pause a playback, and Load (to load a pre-recorded sample file).

If you opt to record a sound sample, you can then save it to disk by typing a name into the File to Save control and clicking on the required file format button below it.

So, that's the right hand side of Figure 3, but what about those complicated-looking buttons on the left? The three buttons—linear, ulaw, and mlaw—all relate to the encoding of the sound sample. Encoding is basically how the sound sample is transferred from the analog domain into the magical digital world. One of the interesting aspects of analog-to-digital conversion (and its opposite, digital to analog) is the fact that it is essentially impossible to exactly match sound in these two domains. The difference may well be impossible to detect by most of us, but it is a well-known effect called quantization error.

The buttons below the encoding button group relate to the sampling interval. The rule of thumb is that the larger the number of samples taken, the better is the reproduction. This is why the default mode in Figure 3 is set to 44,100 samples per second.

Underneath the sample rate buttons, we find the number of bits in a sample word. Again, the higher this is the better because it allows the digital representation to more closely resemble the analogue sample. This is why the default is 16 rather than 8.

Next up, we have the signed and unsigned buttons. The use of signed numbers allows for positive and negative sample values. We're almost done! The choice of little endian versus big endian relates to the manner in which multibyte integer values are ordered. Little endian uses one ordering and big endian uses another. The default is big endian because this is the Java default.

The last button pair in Figure 3 is the mono stereo setting. The default is stereo in order to produce a better sound by using two speakers as opposed to just one speaker.

It's useful to play around with the controls in Figure 3 to see how they affect the sound produced by the program. If you want to record some sound, you'll need some sort of microphone. I used my VoIP phone for this, but many modern computers include a built-in microphone as standard.

The remaining tabs in Figure 3 allow you to use the synthesis options that the Sound API provides. This includes a comprehensive implementation of MIDI synthesis as well as pre-configured tunes. Figure 4 illustrates the MIDI synthesizer.

Figure 4

Figure 4 The MIDI synthesizer

The graphical display at the top of Figure 4 simulates a piano, and you can see it provides a dizzying array of options for the budding musician. It's worth remembering that the code that produces Figure 2 through 4 is just some pretty straightforward Java.

As I've often remarked in the past in relation to design patterns, a small amount of Java can supply you with a disproportionately large amount of power. This is certainly the case here! So, when you've sated your appetite for nifty synthesized tunes, we can look at the last tab option from Figure 2—namely the Groove box as illustrated in Figure 5.

Figure 5

Figure 5 The Groove box

As with the MIDI synthesizer in Figure 4, the Groove box in Figure 5 allows you to combine a rich assortment of sounds to create your required tunes. Who needs iTunes with all this?

Accessing the Sample Code

The sample code for the application described here can be downloaded from Sun Microsystems. Just click on the option called Demo Download and follow the on-screen instructions.

Running the Program as an Applet

If you want to run the program as an applet, you'll have to modify the security settings. Just click on the Options button in Figure 2 and the directions for applet use are displayed.

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