我正在尝试实时生成一组同步音调。但程序产生的所有声音都是“模糊的”，或者是“静态的”，甚至听起来像是背景中的“尖叫声”。这在低音调的声音中尤其明显。 这是代码:
static final long bufferLength = 44100;
static final AudioFormat af = new AudioFormat(bufferLength, 8, 1, true, false);
static boolean go = true; //to be changed somewhere else
static void startSound(double[] hertz) {
if (hertz.length == 0) {return;}
try {
SourceDataLine sdl = AudioSystem.getSourceDataLine(af);
sdl.open();
sdl.start();
int i = 0;
//iterate as long as the sound must play
do {
//create a new buffer
double[] buf = new double[128]; //arbitrary number
final int startI = i;
//iterate through each of the tones
for (int k = 0; k < hertz.length; k++) {
i = startI;
//iterate through each of the samples for this buffer
for (int j = 0; j < buf.length; j++) {
double x = (double)i/bufferLength*hertz[k]*2*Math.PI;
double wave1 = Math.sin(x);
//decrease volume with increasing pitch
double volume = Math.min(Math.max(300 - hertz[k], 50d), 126d);
buf[j] += wave1*volume;
i++;
if (i == 9999999) { //prevent i from getting too big
i = 0;
}
}
}
final byte[] finalBuffer = new byte[buf.length];
//copy the double buffer into byte buffer
for (int j = 0; j < buf.length; j++) {
//divide by hertz.length to prevent simultaneous sounds
// from becoming too loud
finalBuffer[j] = (byte)(buf[j]/hertz.length);
}
//play the sound
sdl.write(finalBuffer, 0, finalBuffer.length);
} while (go);
sdl.flush();
sdl.stop();
} catch (LineUnavailableException e) {
e.printStackTrace();
}
}
//play some deep example tones
startSound(new double[]{65.4064, 58.2705, 48.9995});
我尝试录制该程序输出的声音，波形确实看起来有点锯齿状。但是当我直接从程序打印生成的波形时，它们看起来非常平滑。我发出的声音似乎与扬声器发出的声音不匹配。谁能发现我做错了什么吗？
最佳答案
根据我的评论，我认为您正在听到quantization error由于是 8 位音频，您应该切换到 16 位。量化误差有时称为噪声，但它是一种方波谐波失真，是您听到的微妙泛音的来源。
对于语音等听起来更像噪音的东西，8 位有时是可以接受的。纯音的失真更加明显。
我把你的代码变成了一个粗略的 MCVE来证明差异。
class SoundTest {
static final int bufferLength = 44100;
static final AudioFormat af8 = new AudioFormat(bufferLength, 8, 1, true, false);
static final AudioFormat af16 = new AudioFormat(bufferLength, 16, 1, true, false);
static volatile boolean go = true; //to be changed somewhere else
static void startSound8(double[] hertz) {
if (hertz.length == 0) {return;}
try {
SourceDataLine sdl = AudioSystem.getSourceDataLine(af8);
sdl.open();
sdl.start();
int i = 0;
//iterate as long as the sound must play
do {
//create a new buffer
double[] buf = new double[128]; //arbitrary number
final int startI = i;
//iterate through each of the tones
for (int k = 0; k < hertz.length; k++) {
i = startI;
//iterate through each of the samples for this buffer
for (int j = 0; j < buf.length; j++) {
double x = (double)i/bufferLength*hertz[k]*2*Math.PI;
double wave1 = Math.sin(x);
//decrease volume with increasing pitch
// double volume = Math.min(Math.max(300 - hertz[k], 50d), 126d);
double volume = 64;
buf[j] += wave1*volume;
i++;
if (i == 9999999) { //prevent i from getting too big
i = 0;
}
}
}
final byte[] finalBuffer = new byte[buf.length];
//copy the double buffer into byte buffer
for (int j = 0; j < buf.length; j++) {
//divide by hertz.length to prevent simultaneous sounds
// from becoming too loud
finalBuffer[j] = (byte)(buf[j]/hertz.length);
}
//play the sound
sdl.write(finalBuffer, 0, finalBuffer.length);
} while (go);
sdl.flush();
sdl.stop();
synchronized (SoundTest.class) {
SoundTest.class.notifyAll();
}
} catch (LineUnavailableException e) {
e.printStackTrace();
}
}
static void startSound16(double[] hertz) {
if (hertz.length == 0) {return;}
try {
SourceDataLine sdl = AudioSystem.getSourceDataLine(af16);
sdl.open();
sdl.start();
int i = 0;
//iterate as long as the sound must play
do {
//create a new buffer
double[] buf = new double[128]; //arbitrary number
final int startI = i;
//iterate through each of the tones
for (int k = 0; k < hertz.length; k++) {
i = startI;
//iterate through each of the samples for this buffer
for (int j = 0; j < buf.length; j++) {
double x = (double)i/bufferLength*hertz[k]*2*Math.PI;
double wave1 = Math.sin(x);
//decrease volume with increasing pitch
// double volume = Math.min(Math.max(300 - hertz[k], 50d), 126d);
double volume = 16384;
buf[j] += wave1*volume;
i++;
if (i == 9999999) { //prevent i from getting too big
i = 0;
}
}
}
final byte[] finalBuffer = new byte[buf.length * 2];
//copy the double buffer into byte buffer
for (int j = 0; j < buf.length; j++) {
//divide by hertz.length to prevent simultaneous sounds
// from becoming too loud
int a = (int) (buf[j] / hertz.length);
finalBuffer[j * 2] = (byte) a;
finalBuffer[(j * 2) + 1] = (byte) (a >>> 8);
}
//play the sound
sdl.write(finalBuffer, 0, finalBuffer.length);
} while (go);
sdl.flush();
sdl.stop();
synchronized (SoundTest.class) {
SoundTest.class.notifyAll();
}
} catch (LineUnavailableException e) {
e.printStackTrace();
}
}
static void playTone(final double hz, final boolean fewBits) {
go = true;
new Thread() {
@Override
public void run() {
if (fewBits) {
startSound8(new double[] {hz});
} else {
startSound16(new double[] {hz});
}
}
}.start();
try {
Thread.sleep(5000);
} catch (InterruptedException x) {
x.printStackTrace();
} finally {
go = false;
synchronized (SoundTest.class) {
try {
SoundTest.class.wait();
} catch (InterruptedException x) {
x.printStackTrace();
}
}
}
}
public static void main(String[] args) {
playTone(220, true);
playTone(220, false);
}
}
我讨论了用于打包 16 位字节数组的位操作的概念 here还有示例代码。
还值得一提的是，如果专业应用程序出于某种原因需要使用 8 位，它可能会添加 dither在量化之前，这听起来比纯粹的量化误差更好。 (对于 16 位来说也是如此，但 16 位的量化误差是听不见的，除非它被累积。)
关于java - 使用 SouceDataLine 播放时生成的声音模糊，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38021140/