使用 AudioTrack 生成频率答案

【问题标题】：Generating frequency with AudioTrack使用 AudioTrack 生成频率
【发布时间】：2014-09-30 17:43:10
【问题描述】：

我发现以下代码会产生“噪音”。我希望能够产生音调。据我了解，有某种公式涉及 SIN 来生成音调。

这一行产生噪音：rnd.nextBytes(noiseData);

我尝试手动为所有数组元素分配特定值，但没有声音。我找到了一个生成音调的代码，但它没有流式传输。当我尝试将数据传递给我的代码时，会产生几秒钟的提示音，然后应用程序崩溃。

有什么建议我可以从中生成音调吗？谢谢

public class Internal extends Activity
{   
@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);              
}

public void onPlayClicked(View v)
{
    start();    
}

public void onStopClicked(View v)
{
    stop();
}

boolean m_stop = false;
AudioTrack m_audioTrack;
Thread m_noiseThread;

Runnable m_noiseGenerator = new Runnable()
{       
    public void run()
    {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

        /* 8000 bytes per second, 1000 bytes = 125 ms */
        byte [] noiseData = new byte[1000];
        Random rnd = new Random();

        while(!m_stop)
        {           
            rnd.nextBytes(noiseData);   
            m_audioTrack.write(noiseData, 0, noiseData.length);                 
        }
    }
};

void start()
{
    m_stop = false;

    /* 8000 bytes per second*/
    m_audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 8000, AudioFormat.CHANNEL_OUT_MONO,
                                    AudioFormat.ENCODING_PCM_8BIT, 8000 /* 1 second buffer */,
                                    AudioTrack.MODE_STREAM);            

    m_audioTrack.play();        


    m_noiseThread = new Thread(m_noiseGenerator);
    m_noiseThread.start();
}

void stop()
{
    m_stop = true;          
    m_audioTrack.stop();
}

}

这是生成音调的代码，但是当我将其输出提供给我的写入缓冲区时，它会播放一秒钟然后应用程序崩溃..即使我将“AudioFormat.ENCODING_PCM_8BIT”更改为“AudioFormat.ENCODING_PCM_16BIT”

private final int duration = 1; // seconds
private final int sampleRate = 8000;
private final int numSamples = duration * sampleRate;
private final double sample[] = new double[numSamples];
private final double freqOfTone = 440; // hz

private final byte generatedSnd[] = new byte[2 * numSamples];
    void genTone(){
    // fill out the array
    for (int i = 0; i < numSamples; ++i) {
        sample[i] = Math.sin(2 * Math.PI * i / (sampleRate/freqOfTone));
    }

    // convert to 16 bit pcm sound array
    // assumes the sample buffer is normalised.
    int idx = 0;
    for (final double dVal : sample) {
        // scale to maximum amplitude
        final short val = (short) ((dVal * 32767));
        // in 16 bit wav PCM, first byte is the low order byte
        generatedSnd[idx++] = (byte) (val & 0x00ff);
        generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);

    }
}

【问题讨论】：

标签： android audiotrack

【解决方案1】：

确保您的 noiseData 缓冲区大小大于或等于最小缓冲区大小 AudioTrack 将返回 getMinBufferSize。

http://developer.android.com/reference/android/media/AudioTrack.html#getMinBufferSize(int, int, int)

【讨论】：