JOAL學習筆記第一課單一固定聲源

JOAL學習筆記

最近一直在弄數字音頻處理的一些東西，在網上檢索到了OpenAL的相關資料，粗略閱讀後感覺這個API還是很有魅力的，但JOAL教程的漢化版大多爲低質量機翻，不太適合學習，於是決定自己翻譯一下。

第一次嘗試翻譯英文技術原文，自己也就是六級水平，採用人腦爲主詞典爲輔的方式。不期待有多高的翻譯質量，只希望譯文至少能夠讓讀者連貫地讀完並對其意義正確理解。

在翻譯完每一節時，我會親自調試一下課程中的程序實例，並在這裏記錄下值得注意的問題。

如果看過教程，一定發現了它的代碼部分與文章部分融合到了一起，雖然易於解釋，但對於複製調試來講實在是不方便，因此在每篇對應的筆記中會有該實例對應的連續代碼，以方便複製調試。

下面進入正題，首先是連續的代碼頁

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;

import com.jogamp.openal.AL;
import com.jogamp.openal.ALFactory;
import com.jogamp.openal.util.ALut;

public class SingleStaticSource {
	static AL al = ALFactory.getAL();

	// Buffers hold sound data.
	static int[] buffer = new int[1];;

	// Sources are points emitting sound.
	static int[] source = new int[1];

	// Position of the source sound.
	static float[] sourcePos = { 0.0f, 0.0f, 0.0f };

	// Velocity of the source sound.
	static float[] sourceVel = { 0.0f, 0.0f, 0.0f };

	// Position of the listener.
	static float[] listenerPos = { 0.0f, 0.0f, 0.0f };

	// Velocity of the listener.
	static float[] listenerVel = { 0.0f, 0.0f, 0.0f };

	// Orientation of the listener. (first 3 elements are "at", second 3 are
	// "up")
	static float[] listenerOri = { 0.0f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f };

	static int loadALData() {

		// variables to load into

		int[] format = new int[1];
		int[] size = new int[1];
		ByteBuffer[] data = new ByteBuffer[1];
		int[] freq = new int[1];
		int[] loop = new int[1];

		// Load wav data into a buffer.
		al.alGenBuffers(1, buffer, 0);
		if (al.alGetError() != AL.AL_NO_ERROR)
			return AL.AL_FALSE;
		
		ALut.alutLoadWAVFile("wavdata/0201.wav", format, data, size,freq, loop);//這裏設置你的Wav文件。
		al.alBufferData(buffer[0], format[0], data[0], size[0], freq[0]);

		// Bind buffer with a source.
		al.alGenSources(1, source, 0);

		if (al.alGetError() != AL.AL_NO_ERROR)
			return AL.AL_FALSE;

		al.alSourcei(source[0], AL.AL_BUFFER, buffer[0]);
		al.alSourcef(source[0], AL.AL_PITCH, 1.0f);
		al.alSourcef(source[0], AL.AL_GAIN, 1.0f);
		al.alSourcefv(source[0], AL.AL_POSITION, sourcePos, 0);
		al.alSourcefv(source[0], AL.AL_VELOCITY, sourceVel, 0);
		al.alSourcei(source[0], AL.AL_LOOPING, loop[0]);
		// Do another error check and return.
		if (al.alGetError() == AL.AL_NO_ERROR)
			return AL.AL_TRUE;

		return AL.AL_FALSE;
	}

	static void setListenerValues() {
		al.alListenerfv(AL.AL_POSITION, listenerPos, 0);
		al.alListenerfv(AL.AL_VELOCITY, listenerVel, 0);
		al.alListenerfv(AL.AL_ORIENTATION, listenerOri, 0);
	}

	static void killALData() {
		al.alDeleteBuffers(1, buffer, 0);
		al.alDeleteSources(1, source, 0);
		ALut.alutExit();
	}

	public static void main(String[] args) {
		// Initialize OpenAL and clear the error bit.
		ALut.alutInit();
		al.alGetError();
		// Load the wav data.
		if (loadALData() == AL.AL_FALSE)
			System.exit(-1);

		setListenerValues();

		// Setup an exit procedure.

		Runtime runtime = Runtime.getRuntime();
		runtime.addShutdownHook(new Thread(new Runnable() {
			public void run() {
				killALData();
			}
		}));
		char[] c = new char[1];
		while (c[0] != 'q') {
			try {
				BufferedReader buf = new BufferedReader(new InputStreamReader(
						System.in));
				System.out
						.println("Press a key and hit ENTER: "
								+ "'p' to play, 's' to stop, 'h' to pause and 'q' to quit");
				buf.read(c);
				switch (c[0]) {
				case 'p':
					// Pressing 'p' will begin playing the sample.
					al.alSourcePlay(source[0]);
					break;
				case 's':
					// Pressing 's' will stop the sample from playing.
					al.alSourceStop(source[0]);
					break;
				case 'h':
					// Pressing 'n' will pause (hold) the sample.
					al.alSourcePause(source[0]);
					break;
				}
			} catch (IOException e) {
				System.exit(1);
			}
		}
	}
}

這裏說明一些需要注意的地方

首先是JOAL依賴jar包的下載地址，這裏給出：

http://jogamp.org/deployment/jogamp-current/archive/我下載的是全平臺版本（all-platform）

之後是實例項目所依賴的最小項是哪些，筆者經過幾次組合後確定了兩個必須的jar包爲：joal.jar和gluegen-rt.jar

在調試音頻時我發現，音頻的播放沒有在JVM中創建新的線程：