为什么AudioInputStream read从不返回-1？

Question

我正在读取一个AudioInputStream，并使用它向服务器发出一个分块的POST请求，以便流式传输音频。我不明白为什么流上的read()方法总是返回0，在TargetDataLine上调用stop()和close()之后也是如此。我希望在某个时刻有-1，因为流是关闭的，并且上面没有更多的数据(EOF)。这在进行POST的Apache HTTP客户端调用中引起了问题，因为在某个时刻，它期望-1终止写入输出流，并且以这种方式永远不会终止写入循环。

下面是代码片段：

public class MicrophoneTest {

// record duration, in milliseconds
static final long RECORD_TIME = 5000;

private static AudioFormat audioFormat = new AudioFormat(48000, 16, 1, true, false);

public static void main(String[] args) throws URISyntaxException, IOException {
    final Microphone recorder = new Microphone(audioFormat);

    recorder.open();

    // creates a new thread that waits for a specified
    // of time before stopping
    Thread stopper = new Thread(new Runnable() {
        public void run() {
            try {
                Thread.sleep(RECORD_TIME);
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            }
            recorder.close();
        }
    });

    stopper.start();

    // start recording
    AudioInputStream inputStream = recorder.start();

    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

    byte[] buffer = new byte[1000];
    int read = -1;
    while ((read = inputStream.read(buffer)) != -1) {
        System.out.println(read);
        outputStream.write(buffer);
    }   

    // Never gets here!
}   
}



public class Microphone {

private static final Logger LOGGER = LoggerFactory.getLogger(Microphone.class);

// format of audio file
private static final AudioFileFormat.Type fileType = AudioFileFormat.Type.WAVE;

// the line from which audio data is captured
private TargetDataLine line;

private AudioFormat audioFormat;

public Microphone(AudioFormat audioFormat) {
    this.audioFormat = audioFormat;
}

/**
 * Prepare the line for recording
 * 
 * @return
 */
public boolean open() {
    try {
        Info info = AudioSystem.getMixerInfo()[4];
        line = (TargetDataLine) AudioSystem.getTargetDataLine(audioFormat, info);
        line.open(audioFormat);

    } catch (LineUnavailableException ex) {
        LOGGER.error(ex.toString(), ex);
        return false;
    }
    return true;
}

/**
 * Captures the sound and return the stream
 */
public AudioInputStream start() {

    if (line != null) {

        line.start(); // start capturing

        LOGGER.info("Start recording...");

        return new AudioInputStream(line);

        // AudioSystem.write(ais, fileType, outputStream);

    } else {
        throw new IllegalStateException("Line has not created. Cannot start recording");
    }
}

/**
 * Stops the recording process
 */
public void stop() {
    line.stop();
    LOGGER.info("Stop recording...");
}

/**
 * Closes the target data line to finish capturing and recording     * 
 */
public void close() {
    line.stop();
    line.close();
    LOGGER.info("Data line closed");
}
}

Answer 1

麦克风线路永远不会到达文件的末尾。它要么是打开的，要么是关闭的。它不是从磁盘或内存位置读取文件。

我认为您需要将while循环更改为如下所示：

while(isRecording)
{
    read = inputStream.read(buffer);
    outputStream.write(buffer, 0, read);
}

并让您的stop()方法包含

isRecording = false;

而start()方法包括

isRecording = true;

诸如此类的事情。