小贝子编程

Java SourceDataLine在第一个缓冲区的末尾未调用更新



问题的简短版本：尽管我以前已经使用过它，但这段试图用javax.sound.sampled.SourceDataLine发出一些噪音的代码在第一个缓冲区为空后不会调用update。

编辑：更新了16位立体声的代码。当调用Output.open（format，buffersize）时，声音播放所定义的样本量。

将代码示例提炼为两类项目：

package javaxaudiotest;
import java.io.IOException;
public class JavaxAudioTest {
    public static void main(String[] args) throws IOException {
        JavaxAudioDevice audio = new JavaxAudioDevice();
        audio.create();
        System.out.println("Hit enter to quit.");
        int c = 'a';
        while (c != 'n') {
            c = System.in.read();
        }
        audio.dispose();
    }
}

JavaxAudioDevice与libGDX和我自己的项目特定的东西取出。

package javaxaudiotest;
import java.util.Arrays;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.LineEvent;
import javax.sound.sampled.LineListener;
import javax.sound.sampled.SourceDataLine;
public class JavaxAudioDevice implements LineListener {
    byte[] byteBuf = null;
    boolean quit = false;
    boolean hasquit = false;
    boolean underflow = false;
    SourceDataLine Output;
    int leader = 1024;
    boolean notDoneYet = false;
    boolean alreadyLead = false;
    byte b = 0;

    public int create() {
        quit = false;
        AudioFormat af = new AudioFormat(44100, 16, 2, true, false);
        try {
            Output = AudioSystem.getSourceDataLine(af);
        } catch (Exception e) {
            System.err.println("Failed to create audio device. " + e.getLocalizedMessage());
            return 1;
        }
        if (Output != null) {
            Output.addLineListener(this);
            try {
                Output.open(af,44100*8);
            } catch (Exception e) {
                System.err.println("Failed to open audio device. " + e.getLocalizedMessage());
                return 2;
            }
        }
        System.err.println("Created JavaxAudioDevice");
        while (!Output.isOpen());
        update(null);
        System.err.println(Output.getFormat().toString());
        return 0;
    }

    public void dispose() {
        quit = true;
        Output.close();
        Output.flush();
        Output = null;
        hasquit = true;
    }
//LineListener
    @Override
    public void update(LineEvent le) {
        if (le == null) System.err.println("Audio update");
        else System.err.println("Audio update " + le.toString());
        if ( !quit && ( le == null || le.getType() == LineEvent.Type.STOP ) ) {
            boolean uf = false;
            while (notDoneYet) {
                uf = true;
            }
            notDoneYet = true;
            if (uf) {
                underflow = true;
                System.err.println("underflow");
            }
            if (byteBuf == null) { //insert some leader tape
                short[] shortBuf = new short[44100*8];
                for (int i = 0; i < shortBuf.length; i+=2) {
                    shortBuf[i] = (short)((b++)*50);
                    shortBuf[i+1] = (short)((b++)*200);
                }
                byteBuf = new byte[shortBuf.length * 2];
                for (int i = 0; i < byteBuf.length; ++i) {
                    //little endian
                    if (i % 2 == 0) byteBuf[i] = (byte) (shortBuf[i / 2]); //low byte
                    else byteBuf[i] = (byte) (shortBuf[i / 2] >> 8); //high byte
                }
            }
            Output.write(byteBuf, 0, byteBuf.length);
            Output.start();
            byteBuf = null;
            if (!Output.isRunning()) { //debug
                System.err.println("Output not running");
            } else {
                System.err.println("Output running");
            }
            short[] shortBuf = new short[44100*8];
            for (int i = 0; i < shortBuf.length; i+=2) {
                    if (i%2 == 0) shortBuf[i] = shortBuf[i+1] = (short)((b++)*100);
                    else shortBuf[i] = shortBuf[i+1] = (short)((b++)*150);
            }
            byteBuf = new byte[shortBuf.length * 2];
            for (int i = 0; i < byteBuf.length; ++i) {
                //little endian
                if (i % 2 == 0) byteBuf[i] = (byte) (shortBuf[i / 2]); //low byte
                else byteBuf[i] = (byte) (shortBuf[i / 2] >> 8); //high byte
            }
            notDoneYet = false;
        }
    }
}

以下是一些示例输出：

run:
Created JavaxAudioDevice
Audio update Open event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@4cac0ef5
Audio update
Output running
Audio update Start event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@4cac0ef5
Hit enter to quit.
PCM_SIGNED 44100.0 Hz, 16 bit, stereo, 4 bytes/frame, little-endian
Audio update Stop event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@4cac0ef5
Audio update Close event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@4cac0ef5
BUILD SUCCESSFUL (total time: 7 seconds)

编辑：我用锯齿形生成循环的副本替换了"引导带"。我还将byteBuf初始化为null，以便它激活该部分。此外，我添加了一个循环，等待线路打开，以强制进行第一次更新。现在，我的耳朵里有几分之一秒的锯齿波。不过仍然没有自动更新。

下面的原始问题：

我使用的是libGDX，我编写了一些代码，使一些声音与主线程异步。然后，我将libGDX自己的AsyncExecutor用于几个线程，将AudioDevice用于音频。write（short[]，int，int）正在阻塞，所以我需要在另一个线程中执行它。它是成功的。不幸的是，它有时会结结巴巴（总是在从netbeans运行时）。例如，当我运行gradle任务：desktop:dist时，它会生成一个完整的jar文件，当在Windows10下运行时，它就像一个铃铛一样清晰。

因此，我正在使用javax.sound.sampled（即SourceDataLine）实现pcm输出的桌面特定实现。因此，我创建了一个类，用于启动声音，同时充当SourceDataLine的侦听器。这个类存在于桌面子项目中，并在创建主类时传递给核心子项目。它实现了一个小接口，它是核心的一部分。我把它设置为16位有符号立体声pcm。我在core中有一个类，它生成一个方波并返回一个空头数组。

问题是：除了在开始时调用一次（开始）和在结束时调用几次（停止、关闭）外，我没有听到任何消息，也没有调用update（LineListener的一部分）。

这很奇怪，因为我在以前的一个项目中使用了SourceDataLine作为8位签名的mono-pcm，这是成功的。因此，我还尝试将新版本测试为8位单声道，只从短数组中每隔一个高字节进行测试。SourceDataLine只接受字节数组。

public class JavaxAudioDevice implements AudioInterface, LineListener {
    // omitted stuff
    short[] curBuf;
    byte[] byteBuf;
    SourceDataLine Output;
    int leader = 1024; //leader "tape"
    @Override
    public int create() {
        quit = false;
        AudioFormat af = new AudioFormat(44100, 16, 2, true, false);
//        AudioFormat af = new AudioFormat(44100, 8, 1, true, false);
        try {
            Output = AudioSystem.getSourceDataLine(af);
        } catch (Exception e) {
            System.err.println("Failed to create audio device. " + e.getLocalizedMessage());
            return 1;
        }
        if (Output != null) {
            try {
                Output.open(af,leader);
            } catch (Exception e) {
                System.err.println("Failed to open audio device. " + e.getLocalizedMessage());
                return 2;
            }
            Output.addLineListener(this);
        }
        System.err.println("Created JavaxAudioDevice");
        byte[] bytes = new byte[leader];
        alreadyLead = true;
        Output.write(bytes, 0, bytes.length);
        Output.start();
        System.err.println(Output.getFormat().toString());
        return 0;
    }
//omitted stuff
//LineListener
    @Override
    public void update(LineEvent le) {
            if (le == null) System.err.println("Audio update");
            else System.err.println("Audio update " + le.toString());
        if ( !quit && ( le == null || le.getType() == LineEvent.Type.STOP ) ) {
            boolean uf = false;
            while (notDoneYet) {
                uf = true;
            }
            notDoneYet = true;
            if (uf) {
                underflow = true;
                System.err.println("underflow");
            }
            if (byteBuf == null) { //insert some leader tape
                byteBuf = new byte[leader];
                for (int i = 0; i < byteBuf.length; ++i)
                    byteBuf[i] = 0;
                if (alreadyLead) System.err.println("Using audio leader when not supposed to!");
                else alreadyLead = true;
            }
            Output.write(byteBuf, 0, byteBuf.length);
            Output.start();
            byteBuf = null;
            if (!Output.isRunning()) { //debug
                System.err.println("Output not running");
            } else {
                System.err.println("Output running");
            }
            aplay.call();
            curBuf = aplay.output;
            if (curBuf == null) {
                //I don't know how to help you
                notDoneYet = false;
                System.err.println("Unable to fill buffer");
                return;
            }
            byteBuf = new byte[curBuf.length * 2];
            for (int i = 0; i < byteBuf.length; ++i) {
                //little endian
                if (i % 2 == 0) byteBuf[i] = (byte) (curBuf[i / 2]/*&255/**/); //low byte
                else byteBuf[i] = (byte) (curBuf[i / 2] >> 8); //high byte
            }
//            byteBuf = new byte[curBuf.length/2]; //debug 8 bit mono
//            for (int i = 0; i < byteBuf.length; ++i) {
//                byteBuf[i] = (byte) (curBuf[i*2] >> 8);
//            }
            notDoneYet = false;
        }
    }
}

一些样本输出：

Created JavaxAudioDevice
Audio update Start event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@13ab2987
PCM_SIGNED 44100.0 Hz, 16 bit, stereo, 4 bytes/frame, little-endian
Disposing
Audio update Stop event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@13ab2987
Audio update Close event from line com.sun.media.sound.DirectAudioDevice$DirectSDL@13ab2987
:desktop:run
BUILD SUCCESSFUL
Total time: 33.128 secs

"处置"及以下内容是在我退出程序之后。每秒应该有几个音频更新来重新填充缓冲区。

在这一点上，我不知道下一步该做什么。

好吧，我找到了答案。我之前对javax.sound.sampled主线程的实验涉及生成一个缓冲区，并在检测到完成后重新启动声音。在那个实验中，我在这里试图做的是在SDL中使用类似Mix_HookMusic（）的LineListener（一个更古老的实验）。

https://www.libsdl.org/projects/SDL_mixer/docs/SDL_mixer.html#SEC60

当SDL_mixer的缓冲区用完时，它会调用您提供的函数来生成更多的缓冲区。这不是LineListener在java中的工作方式。当它的缓冲区用完时，它不会被调用。

相反，要像对待自己的线程一样对待它。当您调用SourceDataLine.start（）时，它会在自己的线程中使用start事件类型启动LineListener的事件函数，并返回到主线程。因此，当LineListener检测到启动事件时，它会进入一个循环，该循环生成一个缓冲区并将其写入设备。write（）在有一个或更少的缓冲区时返回。这给了循环足够的时间来制作另一个延迟正好为一个缓冲区的循环。stop（）将启动另一个具有stop类型的LineListener事件函数。现在，事件函数的第二个线程可以设置布尔值，这样第一个线程就知道是时候退出循环了。

下面是一些示例代码，它播放一个音调5秒钟，然后在退出之前再静音5秒钟。

EDIT：似乎至少编写一个框架（我称之为示例）对于确保SourceDataLine.start（）正确工作很重要。由于我使用立体声16位，我需要设备.写（新字节[4]，0,4）；至少在我调用device.start（）之前；

JavaxAudioTest.java

package javaxaudiotest;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.SourceDataLine;
public class JavaxAudioTest {
    public static void main(String[] args) {
        SourceDataLine device;
        int buffer = 44100/15; //buffer in bytes (4 per sample so 60 buffers per second)
        AudioFormat af = new AudioFormat(44100, 16, 2, true, false);
        try {
            device = (SourceDataLine) AudioSystem.getSourceDataLine(af);
        } catch (LineUnavailableException ex) {
            Logger.getLogger(JavaxAudioTest.class.getName()).log(Level.SEVERE, null, ex);
            return;
        }

        WaveGen wg = new WaveGen();
        JavaxAudioDevice jad = new JavaxAudioDevice();
        jad.gen = wg;
        jad.device = device;
        device.addLineListener(jad);
        try {
            device.open(af,buffer);
        } catch (LineUnavailableException ex) {
            Logger.getLogger(JavaxAudioTest.class.getName()).log(Level.SEVERE, null, ex);
            return;
        }
        device.write(new byte[4], 0, 4); //absolutely essential
        device.start();
        System.out.println("Zzzzzzzzzz");
        try {
            Thread.sleep(5000);
        } catch (InterruptedException ex) {
            Logger.getLogger(JavaxAudioTest.class.getName()).log(Level.SEVERE, null, ex);
        }
        System.out.println("zzzzzzzzzzBWAH!");
        device.close();
        try {
            Thread.sleep(5000);
        } catch (InterruptedException ex) {
            Logger.getLogger(JavaxAudioTest.class.getName()).log(Level.SEVERE, null, ex);
        }
        System.out.println("Baiyo");
        device.drain();
        device.close();
    }
}

JavaxAudioDevice.java

package javaxaudiotest;
import javax.sound.sampled.LineEvent;
import javax.sound.sampled.LineListener;
import javax.sound.sampled.SourceDataLine;
public class JavaxAudioDevice implements LineListener {
    boolean quit = false;
    byte[] byteBuf;
    int SampleRate = 44100;
    int buffer = SampleRate/60;
    public WaveGen gen;
    public SourceDataLine device;

    @Override
    public void update(LineEvent event) {
        System.out.println(event.toString());
        if (event.getType() == LineEvent.Type.STOP) {
            quit = true;
        }
        else if (event.getType() == LineEvent.Type.START) {
            while (!quit) {
                short[] buf = new short[buffer];
                for (int i=0; i<buf.length; ++i) {
                    buf[i] = gen.Output();
                }
                byteBuf = new byte[buf.length*4];
                for (int i=0; i<buf.length; ++i) {
                    byteBuf[i*4] = byteBuf[i*4+2] = (byte)buf[i];
                    byteBuf[i*4+1] = byteBuf[i*4+3] = (byte)(buf[i]>>8);
                }
                device.write(byteBuf, 0, byteBuf.length);
            }
        }
    }
}

WaveGen.java

package javaxaudiotest;
public class WaveGen {
    int Wave = 0;
    int Max = 1<<24;
    byte Fidelity = 20;
    int Level = 8;
    int Boost = 2000;
    int Stepper = (int)(110.0/44100*Max); //freq/44100*2^24
    short Output() {
        short ret = 0;
        Wave += Stepper;
        Wave %= Max;
        ret = (short)(( (Wave>>Fidelity)-Level )*Boost);
        return ret;
    }
}

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