Android AudioRecord初始化延迟

这是正在处理的相关代码的示例：

AudioRecord recorder = setupAudio();
recorder.startRecording();

SetupAudio方法：

public AudioRecord setupAudio() {

        AudioRecord recorder;

        minBufferSizeInBytes = AudioRecord.getMinBufferSize(
                RECORDER_SAMPLERATE, AudioFormat.CHANNEL_IN_MONO,
                AudioFormat.ENCODING_PCM_16BIT);

        Log.e("MoverAudio","BufferSize: " + minBufferSizeInBytes);

        recorder = new AudioRecord(MediaRecorder.AudioSource.CAMCORDER,
                RECORDER_SAMPLERATE, AudioFormat.CHANNEL_IN_MONO,
                AudioFormat.ENCODING_PCM_16BIT, minBufferSizeInBytes);

        return recorder;
    }

RECORDER_SAMPLERATE = 8000;

我试图找出是否有任何方法可以缩短初始化时间.

目前,我正在3种设备上对其进行即时测试,结果如下：

银河S3

> setupAudio：〜200ms
> startRecording()：〜280ms

galaxy S3 mini

> setupAudio：〜10ms
> startRecording()：〜290ms

galaxy Nexus

> setupAudio：〜10ms
> startRecording()：〜235ms

缓冲区大小：

>连结：704
> s3：1024
> s3 mini：640

但是,仅来自银河系联系的数据可用.
对于我的应用程序,我必须能够尽快获取音频数据.使用当前值,只有Nexus在可接受的时间内.

S3 mini看起来速度较快,因为它仅比Nexus花费更多,但是前200毫秒的示例被列为0,因此它不可用.

根据我对收集到的数据进行分析后的了解,S3和S3 mini上的音频似乎已经过某种程度的滤波,因为所得到的FFT更加干净,低频声音总是不那么明显.
这是S3mini和galaxy Nexus录制的音频的示例：

http://img41.imageshack.us/img41/4177/ox7h.png
S3迷你

http://img690.imageshack.us/img690/8717/iya6.png
galaxy Nexus

解决方法:

如果请求长缓冲区,则必须等待操作系统以当前采样率填充它.如果您要求的采样率不是硬件ADC正在运行的采样率,则必须另外等待重采样器滤波器的延迟.不同的Android设备和操作系统版本可能支持不同的最小缓冲区大小和本机硬件采样率.

隐藏延迟的一种技术是在应用程序的生命周期中尽早开始录制,并不断丢弃音频样本,直到应用程序需要它们为止.这样就没有启动开销.

补充：在某些设备/操作系统版本上,数据可能确实会以某种硬件采样率(例如在44.1k或48kHz时为4096)捕获到更长的OS驱动程序缓冲区中,并且仅在填充了其中一些缓冲区之后,才转换为另一个采样速率,然后切成较短的请求缓冲区长度,然后音频命令开始向应用发送数据.要绕过,即使有可能,您可能需要修改操作系统并编写自己的ADC驱动程序.但是,请尝试使用较高的采样率(44.1k或48k),并首先请求较短的缓冲区.

Android AudioRecord到文件,然后使用AudioTrack进行播放

基本上,我使用AudioRecord将声音文件录制到sdcard目录中.录制5秒钟,然后使用AudioTrack播放.

好吧,对我来说,录制的文件不存在.可能录制失败.录制时我做错了什么？播放部分呢？

 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    int minBufferSize = AudioTrack.getMinBufferSize(44100, AudioFormat.CHANNEL_CONfigURATION_MONO, 
            AudioFormat.ENCODING_PCM_16BIT);

  audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_CONfigURATION_MONO, 
        AudioFormat.ENCODING_PCM_16BIT, minBufferSize, AudioTrack.MODE_STREAM); 


  recordSound();
 }



private void recordSound(){
    File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/"+"recordsound");
    //    /mnt/sdcard/recordsound
    // Delete any prevIoUs recording.
    if (file.exists())
            file.delete();

    try {
                    file.createNewFile();

                    // Create a DataOuputStream to write the audio data into the saved file.
                    OutputStream os = new FileOutputStream(file);
                    bufferedoutputstream bos = new bufferedoutputstream(os);
                     dos = new DataOutputStream(bos);



                    // Create a new AudioRecord object to record the audio.
                    int bufferSize = audioRecord.getMinBufferSize(FREQUENCY, CHANNEL_CONfigURATION, AUdio_ENCODING);
                     audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, FREQUENCY, CHANNEL_CONfigURATION, AUdio_ENCODING, bufferSize);

                    short[] buffer = new short[bufferSize]; 
                    audioRecord.startRecording();

                    new Timer().schedule(stop(), 5000);  //time in miliseconds

                  //  while (audioRecord.RECORDSTATE_RECORDING==1) 
                    {
                            int bufferReadResult = audioRecord.read(buffer, 0, bufferSize);
                            for (int i = 0; i < bufferReadResult; i++)
                                    dos.writeShort(buffer[i]);
                    }



                   // dos.close();
            } catch (FileNotFoundException e) {
                    // Todo Auto-generated catch block
                    e.printstacktrace();
            } catch (IllegalArgumentException e) {
                    // Todo Auto-generated catch block
                    e.printstacktrace();
            } catch (IllegalStateException e) {
                    // Todo Auto-generated catch block
                    e.printstacktrace();
            } catch (IOException e) {
                    // Todo Auto-generated catch block
                    e.printstacktrace();
            }

}

private TimerTask stop()
{
    TimerTask t = new TimerTask() {

        @Override
        public void run() {
            // Todo Auto-generated method stub
            audioTrack.stop();
            audioTrack.release();
            try {
                dos.close();
            } catch (IOException e) {
                // Todo Auto-generated catch block
                e.printstacktrace();
            }



             try {
                    playfilesound();
                } catch (IOException e) {
                    // Todo Auto-generated catch block
                    e.printstacktrace();
                }



        }
    };
    return t;

}


private void playfilesound() throws IOException
{




    int count = 512 * 1024; // 512 kb
    //Reading the file..
    byte[] byteData = null; 
    File file = null; 
    file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/"+"recordsound");    //filePath

     if (file.exists())
     {
         int a=0;


     }

    byteData = new byte[(int)count];
    FileInputStream in = null;
    try {
    in = new FileInputStream( file );

    } catch (FileNotFoundException e) {
    // Todo Auto-generated catch block
    e.printstacktrace();
    }


    int bytesread = 0, ret = 0;
    int size = (int) file.length();
    audioTrack.play();


    while (bytesread < size) {    // Write the byte array to the track 
        ret = in.read( byteData,0, count);   //ret =size in bytes

        if (ret != -1) {
            audioTrack.write(byteData,0, ret);
            bytesread += ret; }  //ret
        else break; }   //while

        in.close(); audioTrack.stop(); audioTrack.release();
    }  

解决方法:

如果您的要求是在录制时应该播放(意味着循环播放音频),则在while循环线程中,您正在存储录制的数据(audioData bufer),您可以在while循环中将其本身复制到播放器对象( player.write(audioData,0,numShortsRead);).您说您的UI线程被卡住了,这可能是因为您给Audio Record线程赋予了更高的优先级.

检查以下我用于上述回送要求的代码：

boolean m_isRun=true;
    public void loopback() {
            // Prepare the AudioRecord & AudioTrack
            try {
                buffersize = AudioRecord.getMinBufferSize(SAMPLE_RATE,
                        AudioFormat.CHANNEL_CONfigURATION_MONO,
                        AudioFormat.ENCODING_PCM_16BIT);

            if (buffersize <= BUF_SIZE) {
                buffersize = BUF_SIZE;
            }
            Log.i(LOG_TAG,"Initializing Audio Record and Audio Playing objects");

            m_record = new AudioRecord(MediaRecorder.AudioSource.MIC,
                    SAMPLE_RATE, AudioFormat.CHANNEL_CONfigURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT, buffersize * 1);

            m_track = new AudioTrack(AudioManager.STREAM_ALARM,
                    SAMPLE_RATE, AudioFormat.CHANNEL_CONfigURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT, buffersize * 1,
                    AudioTrack.MODE_STREAM);

            m_track.setPlaybackRate(SAMPLE_RATE);
        } catch (Throwable t) {
            Log.e("Error", "Initializing Audio Record and Play objects Failed "+t.getLocalizedMessage());
        }

        m_record.startRecording();
        Log.i(LOG_TAG,"Audio Recording started");
        m_track.play();
        Log.i(LOG_TAG,"Audio Playing started");

        while (m_isRun) {
            m_record.read(buffer, 0, BUF_SIZE);
            m_track.write(buffer, 0, buffer.length);
        }

        Log.i(LOG_TAG, "loopback exit");
    }

    private void do_loopback() {
        m_thread = new Thread(new Runnable() {
            public void run() {
                loopback();
            }
        });

还有一件事,如果您的要求是先录制几秒钟然后播放,则在播放时应该重新开始录制,您可以使用带有超时的延迟处理程序线程来执行此操作,在该线程中您可以停止录制并复制缓冲区,然后开始录制.

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