209 lines
8.2 KiB
HTML
209 lines
8.2 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>OpenAL Tutoral</title>
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<meta http-equiv="content-type"
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content="text/html; charset=windows-1252">
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<meta name="author" content="Brian Matzon">
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<meta name="description" content="Basic sound using OpenAL">
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</head>
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<body>
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<h1 align="center">OpenAL Tutorial<br>
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<font size="-1">(by Brian Matzon <<a href="mailto:brian@matzon.dk">brian@matzon.dk</a>>)</font><br>
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</h1>
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<b>1.0 OpenAL Basics</b><br>
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Before embarking on our little OpenAL adventure, some tools are needed.<br>
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<br>
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<b>1.0.1 Ingredients</b><br>
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Head on over to Creatives <a
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href="http://developer.creative.com/scripts/DC_D&H_Games-Downloads.asp?opt=2">site</a>
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and snag a copy of the OpenAL specification along with a copy of the Programmers
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reference.<br>
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If you haven't already done so, get a copy of the OpenAL runtime environment
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too (and install it).<br>
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<br>
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<b>1.1 OpenAL theory</b><br>
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Uhm... I'm not going to write this... In all honesty reading the specification
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would be a good thing before continuing - but it isn't required...<br>
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<br>
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<b>1.2 Basic setup</b><br>
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Lets start out by creating a skeleton class for some very basic sound. We'll
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start of by creating the required OpenAL objects<br>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>import
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org.lwjgl.openal.AL;<br>
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import org.lwjgl.openal.ALC;<br>
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import org.lwjgl.openal.ALCcontext;<br>
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import org.lwjgl.openal.ALCdevice;<br>
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import org.lwjgl.openal.ALUT;<code></code><br>
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<br>
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public class PlayTest {<br>
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<br>
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/** OpenAL instance */<br>
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protected AL al;<br>
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<br>
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/** OpenAL Context instance */<br>
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protected ALC alc;<br>
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<br>
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/** OpenAL Util library instance */<br>
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protected ALUT alut;<br>
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<br>
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/** OpenAL context */<br>
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protected ALCcontext context;<br>
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<br>
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/** OpenAL device */<br>
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protected ALCdevice device; <br>
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<br>
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/**<br>
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* Creates an instance of PlayTest<br>
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*/<br>
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public PlayTest() {<br>
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try {<br>
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</tt> <tt> al = new AL();<br>
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alc = new ALC();<br>
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alut = new ALUT();<br>
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<br>
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al.create();<br>
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alc.create();<br>
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alut.create();<br>
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} catch (Exception e) {<br>
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e.printStackTrace();<br>
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}</tt><tt><br>
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}<br>
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}</tt><code></code></p>
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We need instances of the following classes:<br>
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<ul>
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<li><tt>AL </tt>- basic source, buffer and listener interaction</li>
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<li><tt>ALC </tt>- context and device creatiuon</li>
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<li><tt>ALUT </tt>- OpenAL utility class</li>
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</ul>
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<b>1.3 OpenAL initialization</b><br>
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Now that we have created a basic class containing instances of the relevant
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OpenAL classes, lets start of by initializing OpenAL - that is create a device
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and a context:<br>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"> <tt>
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/**<br>
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* Initializes OpenAL<br>
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*/<br>
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protected void alInitialize() { <br>
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//get default device<br>
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device = alc.openDevice(null);<br>
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<br>
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//create context (no attributes specified)<br>
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context = alc.createContext(device, 0);<br>
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<br>
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//make context current<br>
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alc.makeContextCurrent(context);<br>
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}</tt><code><br>
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</code></p>
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Start of by opening a device using the <tt>openDevice </tt>method. <tt>openDevice
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</tt>takes a <tt>String </tt>as argument, containing the name of the device
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to open. If no name is supplied, the default device will be used (OpenAL
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currently doesn't support enumeration of devices available).<br>
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<br>
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Having opened a device, create a context to that device using <tt>createContext</tt>.
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<tt>createContext</tt> takes two arguments: device to use and a list of attributes
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(see specification for list of attributes). Since we're going by default context,
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we just specify <tt>0</tt> for attributes.<br>
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<br>
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Finish of by making the created context current. Do this by calling <tt>makeContextCurrent</tt>,
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supplying just created context as argument.<br>
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<p><b>1.4 Buffer and Source creation</b><br>
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Now that we have opened a device and gotten a context, we need to create
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two things to actually get some sound. We need to create a buffer to hold
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sounddata, and a source that is to play the sounddata.<br>
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Lets start of by creating one source, and one buffer:</p>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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//create one IntBuffer as buffer and one as source<br>
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IntBuffer buffers = createIntBuffer(1);<br>
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IntBuffer sources = createIntBuffer(1);<br>
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<br>
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//generate buffers and sources<br>
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al.genBuffers(1, Sys.getDirectBufferAddress(buffers));<br>
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al.genSources(1, Sys.getDirectBufferAddress(sources));</tt></p>
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<p>There, all set for actually loading some sounddata into the buffer.<br>
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</p>
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<b>1.5 Loading sounddata and setting up a buffer</b><br>
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Now that we have a buffer, we need to load some sound data into this buffer.
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This is done using the <tt>al.bufferData</tt> method. In our example we will
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cheat a bit, by using the <tt>ALUT </tt>method <tt>loadWAVFile</tt> to load
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a wave file, and copy this into the buffer:<br>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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//load wave data<br>
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ALUTLoadWAVData file = alut.loadWAVFile("myfile.wav");<br>
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<br>
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//copy to buffer<br>
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al.bufferData(buffers.get(0), file.format, file.data, file.size, file.freq);<br>
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<br>
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//unload file again<br>
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alut.unloadWAV(file.format, file.data, file.size, file.freq); <br>
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</tt></p>
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Having loaded the data, we pass it to <tt>bufferData</tt>. Once the buffer
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has been filled with sounddata, we unload it from the system using <tt>alut.unloadWAV</tt>.
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Don't worry about deleting it this soon - the sounddata has been <b>copied</b>
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to the buffer.<br>
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<br>
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<b>1.6 Associating sources and buffers</b><br>
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To associate a source to a buffer we set the integer BUFFER attribute on
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the source, and assign it a value of the buffer to play:<br>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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//set up source input<br>
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al.sourcei(sources.get(0), AL.BUFFER, buffers.get(0));</tt><tt><br>
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</tt></p>
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<b>1.7 Setting source properties</b><br>
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Having set up the source, it is time to set some attributes on the source
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- there are many that can be set, but in this example we only set the looping
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attribute to true by doing the following:<br>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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//loop source<br>
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al.sourcei(sources.get(0), AL.LOOPING, AL.TRUE);</tt><tt><br>
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</tt></p>
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<b>1.8 Sound...<br>
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</b>There, ready to play the sound, do this using the <tt>sourcePlay </tt>method
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of the <tt>AL </tt>class. to stop and pause use <tt>sourcePause </tt>and
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<tt>sourceStop </tt>respectively, and supply the source to affect:<br>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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//play source 0<br>
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al.sourcePlay(sources.get(0));<br>
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<br>
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//wait 5 secs<br>
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try {<br>
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System.out.println("Waiting 5 seconds for sound to complete");<br>
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Thread.sleep(5000);<br>
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} catch (InterruptedException inte) {<br>
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}<br>
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<br>
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//stop source 0<br>
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al.sourceStop(sources.get(0));</tt></p>
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<b>1.9 Cleaning up<br>
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</b>Having had loads of fun playing a sound (!), it is now time to do some
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house chores. We need to clean up what we have created, this amounts to:<br>
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- deleting source and buffer<br>
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- deleting context<br>
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- closing devce<br>
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as is shown here:<b><br>
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</b>
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<p
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style="border-style: solid; border-width: 1px; padding: 3px; background-color: rgb(255,255,204);"><tt>
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//delete buffers and sources<br>
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al.deleteSources(1, Sys.getDirectBufferAddress(sources));<br>
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al.deleteBuffers(1, Sys.getDirectBufferAddress(buffers));<br>
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<br>
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//shutdown<br>
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alc.makeContextCurrent(null);<br>
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alc.destroyContext(context);<br>
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alc.closeDevice(device);</tt></p>
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There, all set. Now you should be able to play some basic sound!<br>
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This tutorial is rather short, and the above examples feature no error checking.
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For the complete source code, look at:<br>
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<tt>org.lwjgl.openal.BasicTest</tt> in the repository.<br>
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</body>
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</html>
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