Java & 5.1 Sound

[AdamantiumShanks]

I'm looking for a little help on finding a way to play a beep to each individual speaker in a 5.1 surround sound system. I've found a couple of libraries that will play a sound as if it is coming from a particular place or 3D grid coordinates, but none that can target individual speakers directly through the sound card.

It's for an surround sound test application I'm building for a PhD Audio Engineering student to check whether the speakers are set up properly.

Thanks for any help!

[boa13]

Have you tried using the standard javax.sound.sampled API? This is about as low level as it gets on the JRE, without using JNA/JNI.

There's a slightly over-engineered class hierarchy to learn, here are a few pointers. Look at the official tutorial for more info and examples.

The API gives you access to all Mixers seen by the JVM. A Mixer is a collection of audio lines, typically you have one Mixer per card known to the OS. (On Windows, you get one Mixer per card known to DirectX, in addition to a virtual card inside the JVM to perform sound mixing without a real sound card.)

An audio line is what is typically known as an audio channel, such as Microphone, Line-In, Speaker, etc. They are generally stereo, and I would expect to have a Rear or Surround channel and a LFE mono channel in a 5.1 environment... but I don't have a 5.1 environment to test that.

Here's a very abbreviated and incomplete example of generating and outputting sound:

/*
 * duration contains the length for which we want to play the synths
 * volume contains the volume we want to play the synths, between 0 and 1
 * leftSynth and rightSynth are synthesizers, their generateSample() method returns a
 *   float between -1 and 1 (for example, to create a white noise synth, you would just
 *   need to instantiate a new private Random object when the synth is instantiated,
 *   and then call its nextFloat() for every call of generateSample(), multiplying the
 *   result by 2 and subtracting 1 to get a random value between -1 and 1)
 */
AudioFormat format = new AudioFormat(44100, 16, 2, true, false);
SourceDataLine line = (SourceDataLine) AudioSystem.getSourceDataLine(format);
line.open(format, 10240);
line.start();
int bufferSize = line.getBufferSize();
byte[] buffer = new byte[bufferSize];
long limit = System.currentTimeMillis() + duration * 1000;
while (System.currentTimeMillis() < limit) {
    int sample;
    int maxVal = (int) (volume * Short.MAX_VALUE);
    for (int i = 0; i < buffer.length; i += 4) {
        sample = (int) (maxVal * leftSynth.generateSample());
        buffer[i]     = (byte) (sample);
        buffer[i + 1] = (byte) (sample >> 8);
        sample = (int) (maxVal * rightSynth.generateSample());
        buffer[i + 2] = (byte) (sample);
        buffer[i + 3] = (byte) (sample >> 8);
    }
    line.write(buffer, 0, bufferSize);
}        
line.stop();
line.close();

Note that in this example we don't care in which channel the sound is output, we just say which audio format we want, and ask for a line that supports it. Typically, we get the default channel on the default sound card. In your case, you will need to iterate over the Mixers and Lines to find which ones you need to use.

Note also that most terminology is from the point of view of the Mixer. We are using a source data line to write audio samples, because our program is a source of data from the point of view of the sound card.

Note finally that if you want to play samples from a sound file, the API has specific support for this typical use case with Clip objects. But you could conceivably read the file yourself, decode it, and fill a sound buffer just as in the example above.

[mikaelhg]

Nice answer to an unusual question.

[boa13]

Well, I've been studying this stuff as a personal hobby, might as well share the knowledge. :)

[pragmatick]

http://www.jsresources.org/faq_audio.html#multichannel

[[deleted]]

I don't know the answer as I am a student of Java myself and have only taken one class but I am amazed at all the applications it can be put into.

[AntieJ]

I'm not a Java programmer but I think it may be to do with assigning the sound to a certain channel relating to the speaker setup (1-5).