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 http://jackaudio.org/faq/。
让 Jack 在 Raspberry Pi 上运行有点麻烦。有好资料here https://wiki.linuxaudio.org/wiki/raspberrypi.
I use JnaJack https://github.com/jaudiolibs/jnajackwith 提供了 Java 和 Jack 之间的接口。
您无法在 Raspbian 上开箱即用地运行 Jack。 Debian Wheezy 有补丁，但 Raspbian Jessie 似乎没有。因此，您需要创建一个不使用 DBus 的 Jackd2 版本。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。他们告诉你要修补的其他所有内容现在都已默认在 Raspbian 中修补，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 中进行更改
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 JnaJack 源代码中的 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通道中的每个通道中播放正弦波两秒钟。我还没有尝试过输入通道，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 ...
那么你在连接它时就会遇到问题。
您可以使用 QJackCtl 查看 Jack 设置，您可以在 Raspberry Pi 上运行该设置，并通过另一台计算机上的 X 服务器进行访问。我没能在 Pi 上运行 X Windows。
如果你想通过Jack播放wav文件，this http://www.labbookpages.co.uk/audio/javaWavFiles.html是一个很好的例子，展示了如何读取 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。最好打开您打算使用的所有端口，调用client.activate()，并在 JackCallback 中将音频文件中的通道路由到声卡中的相应通道。您可以使用qjackctl看看杰克发生了什么。
