编辑:我现在使用的是 Jack(Jack 音频连接套件)。请参阅下面的答案。

我的 Raspberry Pi 上有一个声卡，有 8 个输出 channel (四个立体声 channel )，一个 Octosound 卡。我想要做的是选择其中一个 channel 将声音路由到。 使用此代码，我打印声卡的信息:

mixers = AudioSystem.getMixerInfo();
    for (Mixer.Info mixerInfo : mixers) {
        logger.debug("\n");
        logger.debug("Found Mixer: " + mixerInfo);

        Mixer m = AudioSystem.getMixer(mixerInfo);

        Line.Info[] sourceLines = m.getSourceLineInfo();
        for (Line.Info li : sourceLines) {
            logger.debug("Found source line: " + li + " " + li.getClass());

            if (li instanceof Port.Info) {
                Port.Info portInfo = (Port.Info) li;
                logger.debug("port found " + portInfo.getName() + " is source " + portInfo.isSource());
                sourceDataLines.add(portInfo);
            }

        }

        Line.Info[] targetLines = m.getTargetLineInfo();

        for (Line.Info li : targetLines) {
            logger.debug("Found target line: " + li + " " + li.getClass());
            outputLines.add(li);

            if (li instanceof Port.Info) {
                Port.Info portInfo = (Port.Info) li;
                logger.debug("port found " + portInfo.getName() + " is source " + portInfo.isSource());
                outputPorts.add(portInfo);
            }
        }
    }


private void lineClose(int soundPort) throws LineUnavailableException {
    Port.Info lineInfo = outputPorts.get(soundPort);
    Line line = (Port) AudioSystem.getLine(lineInfo);
    line.close();
}

private void lineOpen(int l) throws LineUnavailableException {

    for (int i = 0; i < outputPorts.size(); i++) {
        Port.Info lineInfo = outputPorts.get(i);
        Line line = (Port) AudioSystem.getLine(lineInfo);
        if (l == i) {
            line.open();
        } else {
            line.close();
        }
    }
}

这是我得到的输出:

Found Mixer: audioinjectoroc [default], version 4.9.41-v7+
Found source line: interface SourceDataLine supporting 84 audio formats, and buffers of at least 32 bytes class com.sun.media.sound.DirectAudioDevice$DirectDLI
Found source line: interface Clip supporting 84 audio formats, and buffers of at least 32 bytes class com.sun.media.sound.DirectAudioDevice$DirectDLI
Found target line: interface TargetDataLine supporting 84 audio formats, and buffers of at least 32 bytes class com.sun.media.sound.DirectAudioDevice$DirectDLI

Found Mixer: audioinjectoroc [plughw:0,0], version 4.9.41-v7+
Found source line: interface SourceDataLine supporting 96 audio formats, and buffers of at least 32 bytes class com.sun.media.sound.DirectAudioDevice$DirectDLI
Found source line: interface Clip supporting 96 audio formats, and buffers of at least 32 bytes class com.sun.media.sound.DirectAudioDevice$DirectDLI
Found target line: interface TargetDataLine supporting 96 audio formats, and buffers of at least 32 bytes class com.sun.media.sound.DirectAudioDevice$DirectDLI

Found Mixer: Port audioinjectoroc [hw:0], version 4.9.41-v7+
Found source line: ADC1 source port class com.sun.media.sound.PortMixer$PortInfo
port found ADC1 is source true
Found source line: ADC2 source port class com.sun.media.sound.PortMixer$PortInfo
port found ADC2 is source true
Found source line: ADC3 source port class com.sun.media.sound.PortMixer$PortInfo
port found ADC3 is source true
Found target line: DAC1 target port class com.sun.media.sound.PortMixer$PortInfo
port found DAC1 is source false
Found target line: DAC2 target port class com.sun.media.sound.PortMixer$PortInfo
port found DAC2 is source false
Found target line: DAC3 target port class com.sun.media.sound.PortMixer$PortInfo
port found DAC3 is source false
Found target line: DAC4 target port class com.sun.media.sound.PortMixer$PortInfo
port found DAC4 is source false

现在这是我用来从 wav 文件输出声音的代码:

   String path = soundDirectory + soundUrl;
   InputStream is = new FileInputStream(path);
   BufferedInputStream bis = new BufferedInputStream(is);
   AudioInputStream inputStream = AudioSystem.getAudioInputStream(bis);
   AudioFormat format = inputStream.getFormat();

   Mixer.Info mi = mixers[0];

   SourceDataLine sourceDataLine = (SourceDataLine) AudioSystem.getSourceDataLine(format,mi);
   sourceDataLine.open(format);
   sourceDataLine.start();
   byte[] buf = new byte[1024];
   int bytesRead;
   while ((bytesRead = inputStream.read(buf)) != -1){
       sourceDataLine.write(buf, 0, bytesRead);
   }
   inputStream.close();

   sourceDataLine.drain();
   sourceDataLine.stop();
   sourceDataLine.close();

   lineClose(soundPort);

我已经尝试了很多方法，但在所有情况下，所有输出都会发出声音。

最佳答案

我自己找到了解决方案。我现在使用 Jack(Jack 音频连接套件，请参阅 here。 让 Jack 在 Raspberry Pi 上运行有点麻烦。有好资料here .

我使用 JnaJack with 提供 Java 和 Jack 之间的接口(interface)。

您不能开箱即用地在 Raspbian 上运行 Jack。 Debian Wheezy 有补丁，但 Raspbian Jessie 似乎没有。所以你需要创建一个不使用 DBus 的 Jackd2 版本。 Here它解释了如何在没有 DBus 的情况下构建 Jackd2。有一个障碍:您所要做的就是删除引用 DBus 的两行。他们告诉您要打补丁的所有其他内容现在都默认在 Raspbian 中打了补丁，或者看起来是这样。您需要替换这些行: 下载源代码后，在 debian/rules 中更改

waf-configure-options += $(if $(filter linux,$(DEB_HOST_ARCH_OS)),--alsa --dbus) 
became
waf-configure-options += $(if $(filter linux,$(DEB_HOST_ARCH_OS)),--alsa)

dh_install -pjackd2 debian/tmp/usr/share/dbus-1/*
became
#dh_install -pjackd2 debian/tmp/usr/share/dbus-1/*

我修改了在 JnaJack 源代码中找到的 SimpleAudioClient 示例:

public class SimpleAudioClient {

    private boolean autoconnect = true;
    private JackClient client;
    private Processor processor;
    private Callback callback;
    private ShutDownHook shutDownHook;
    private JackPort[] inputPorts;
    private JackPort[] outputPorts;
    private FloatBuffer[] inputBuffers;
    private FloatBuffer[] outputBuffers;
    private float samplerate;
    private int buffersize;
    private volatile boolean active;

    private Logger logger = Logger.getLogger(getClass().getSimpleName());
    private int channelNumber = 0;

    public SimpleAudioClient() throws JackException {

        Jack jack = Jack.getInstance();
        logger.debug("Jack instance " + jack.toString());
        EnumSet<JackOptions> options = EnumSet.of(JackOptions.JackNoStartServer);
        EnumSet<JackStatus> status = EnumSet.noneOf(JackStatus.class);
        try {
            client = jack.openClient("jna_jack", options, status);
        } catch (JackException ex) {
            System.out.println("ERROR : Status : " + status);
            throw ex;
        }

        String[] inputs = new String[0];
        inputPorts = new JackPort[inputs.length];
        EnumSet<JackPortFlags> flags = EnumSet.of(JackPortFlags.JackPortIsInput);
        for (int i = 0; i < inputs.length; i++) {
            //inputPorts[i] = client.registerPort(inputs[i], JackPortType.AUDIO, flags);
        }

        String[] outputs = new String[]{"playback_1", "playback_2", "playback_3", "playback_4", "playback_5", "playback_6", "playback_7", "playback_8"};
        outputPorts = new JackPort[outputs.length];
        flags = EnumSet.of(JackPortFlags.JackPortIsOutput);
        for (int i = 0; i < outputs.length; i++) {
            outputPorts[i] = client.registerPort(outputs[i], JackPortType.AUDIO, flags);
        }

        processor = new SineAudioSource();

        this.inputBuffers = new FloatBuffer[inputPorts.length];
        this.outputBuffers = new FloatBuffer[outputPorts.length];
        this.callback = new Callback();
        this.shutDownHook = new ShutDownHook();
        client.onShutdown(shutDownHook);

        for (JackPort port : inputPorts) {
            logger.debug("input port " + port.getType() + " " + port.getName());
        }

        for (JackPort port : outputPorts) {
            logger.debug("output port " + port.getType() + " " + port.getName());
        }
    }

    public void activate(int channelNr) throws JackException {

        this.channelNumber = channelNr;

        try {
            samplerate = client.getSampleRate();
            System.out.println("Sample rate = " + samplerate);
            buffersize = client.getBufferSize();
            System.out.println("Buffersize = " + buffersize);
            processor.setup(samplerate, buffersize);
            active = true;
            client.setProcessCallback(callback);
            client.activate();
            if (autoconnect) {
                doAutoconnect();
            }
        } catch (Exception ex) {
            active = false;
            throw new JackException("Could not activate Jack client");
        }
    }

    private void doAutoconnect() throws JackException {
        Jack jack = Jack.getInstance();
        String[] physical = jack.getPorts(client, null, JackPortType.AUDIO,
                EnumSet.of(JackPortFlags.JackPortIsInput, JackPortFlags.JackPortIsPhysical));
        int count = Math.min(outputPorts.length, physical.length);
        for (int i = 0; i < count; i++) {
            logger.debug("output port " + outputPorts[i].getName());
            jack.connect(client, outputPorts[i].getName(), physical[i]);
        }
        physical = jack.getPorts(client, null, JackPortType.AUDIO,
                EnumSet.of(JackPortFlags.JackPortIsOutput, JackPortFlags.JackPortIsPhysical));
        count = Math.min(inputPorts.length, physical.length);
        for (int i = 0; i < count; i++) {
            logger.debug("input port " + inputPorts[i].getName());
            //jack.connect(client, physical[i], inputPorts[i].getName());
        }
    }

    public void shutdown() {
        active = false;
        client.deactivate();
        client.close();
    }

    private void processBuffers(int nframes) {
        for (int i = 0; i < inputPorts.length; i++) {
            inputBuffers[i] = inputPorts[i].getFloatBuffer();
        }
        for (int i = 0; i < outputPorts.length; i++) {
            outputBuffers[i] = outputPorts[i].getFloatBuffer();
        }
        processor.process(channelNumber, inputBuffers, outputBuffers);
    }

    private class Callback implements JackProcessCallback {

        public boolean process(JackClient client,final int nframes) {

            if (!active) {
                return false;
            } else {
                try {
                    processBuffers(nframes);
                    return true;
                } catch (Exception ex) {
                    System.out.println("ERROR : " + ex);
                    active = false;
                    return false;
                }

            }
        }
    }

    private class ShutDownHook implements JackShutdownCallback {

        public void clientShutdown(JackClient client) {
            active = false;
            processor.shutdown();
        }
    }

    public static interface Processor {

        public void setup(float samplerate, int buffersize);

        public void process(int channelNumber, FloatBuffer[] inputs, FloatBuffer[] outputs);

        public void shutdown();
    }

    /**
     * Create a SimpleAudioClient.
     *
     * @return client
     * @throws org.jaudiolibs.jnajack.JackException
     */
    public static SimpleAudioClient create(
    ) throws JackException {

        return new SimpleAudioClient();
    }
}

我将示例代码中的 SineAudioClient 修改为:

public class SineAudioSource implements SimpleAudioClient.Processor {

    private final static int TABLE_SIZE = 200;
    private int left_phase = 0;
    private int right_phase = 0;
    private float[] data;

    public void setup(float samplerate, int buffersize) {
        data = new float[TABLE_SIZE];
        for (int i = 0; i < TABLE_SIZE; i++) {
            data[i] = (float) (0.2 * Math.sin(((double) i / (double) TABLE_SIZE) * Math.PI * 2.0));
        }
    }

    public void process(int channelNumber, FloatBuffer[] inputs, FloatBuffer[] outputs) {

        FloatBuffer left = outputs[channelNumber];
        int size = left.capacity();
        for (int i = 0; i < size; i++) {
            left.put(i, data[left_phase]);
            left_phase += 2;
            right_phase += 3;
            if (left_phase >= TABLE_SIZE) {
                left_phase -= TABLE_SIZE;
            }
        }
    }

    public void shutdown() {
        System.out.println("Sine Audio Source shutdown");
    }
}

因此它在声卡的八个 channel 中的每个 channel 中播放两秒钟的正弦波。我还没有尝试过输入 channel ，我读到当输入和输出都被激活时，很难让 Jack 在 Raspbian 上工作。

我在运行我的应用程序之前启动 Jack，启动命令是

/usr/bin/jackd -dalsa -dhw:audioinjectoroc -r48000 -p1024 -n2 -P &

启动jack时的日志应该显示

creating alsa driver ... hw:audioinjectoroc|-|1024|2|48000|0|0|nomon|swmeter|-|32bit

其中“audioinjector”是声卡的名称。如果显示

...hw:audioinjectoroc|hw:audioinjectoroc|1024 ...

那么您将无法连接到它。

您可以使用 QJackCtl 查看 Jack 设置，您可以在您的 Raspberry Pi 上运行它并从另一台计算机使用 X 服务器进行访问。我没能在 Pi 上运行 X Windows。

如果您想通过 Jack 播放 wav 文件，this是一个很好的例子，说明如何读取 wav 文件并将其提供给 jack。

编辑:该示例是一个很好的起点，但您需要进行一些更改。最好打开您计划使用的所有端口，调用 client.activate()，并在 JackCallback 中将 channel 从您的音频文件路由到声卡中的适当 channel 。您可以使用 qjackctl 查看 Jack 中发生了什么。

关于java - 在java中为八 channel 声卡选择输出行，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45821554/