Android音频可视化

相关链接：

Android 调用自带的录制音频程序
http://www.eoeandroid.com/thread-78949-1-1.html

 MediaRecoder实现音频录制并播放
http://www.eoeandroid.com/thread-237311-1-1.html

Android 音频的介绍
http://www.eoeandroid.com/thread-68377-1-1.html

--------------帖子正文----------------

先看一下效果图：

public class FFTActivity extends Activity implements OnClickListener{
        private Button button;
        private ImageView imageView;
        private int frequency = 8000;
        private int channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO;
        private int audioEncoding = AudioFormat.ENCODING_PCM_16BIT;
        private RealDoubleFFT transformer;
        private int blockSize = 256;
        private boolean started = false;
        private Canvas canvas;
        private Paint paint;
        private Bitmap bitmap;
 
        @Override
        protected void onCreate(Bundle savedInstanceState) {
 
                super.onCreate(savedInstanceState);
                setContentView(R.layout.fft);
                button = (Button) findViewById(R.id.fft_button);
                button.setOnClickListener(this);
                imageView = (ImageView) findViewById(R.id.fft_imageView);
                transformer = new RealDoubleFFT(blockSize);
                bitmap = Bitmap.createBitmap(256, 100, Bitmap.Config.ARGB_8888);
                canvas = new Canvas(bitmap);
                paint = new Paint();
                paint.setColor(Color.GREEN);
                imageView.setImageBitmap(bitmap);
 
        }
 
        private class RecordAudio extends AsyncTask<Void, double[], Void> {
 
                @Override
                protected Void doInBackground(Void... params) {
                        int bufferSize = AudioRecord.getMinBufferSize(frequency,
                                        channelConfiguration, audioEncoding);
                        AudioRecord audioRecord = new AudioRecord(
                                        MediaRecorder.AudioSource.MIC, frequency,
                                        channelConfiguration, audioEncoding, bufferSize);
                        short[] buffer = new short[blockSize];
                        double[] toTransform = new double[blockSize];
                        audioRecord.startRecording();
                        while (started) {
                                //将record的数据 读到buffer中，但是我认为叫做write可能会比较合适些。
                                int bufferResult = audioRecord.read(buffer, 0, blockSize);
 
                                for (int i = 0; i < bufferResult; i++) {
                                        toTransform<i> = (double) buffer<i> / Short.MAX_VALUE;
                                }
                                transformer.ft(toTransform);
                                publishProgress(toTransform);
                        }
                        audioRecord.stop();
                        return null;
                }
 
                @Override
                protected void onProgressUpdate(double[]... values) {
 
                        super.onProgressUpdate(values);
                        canvas.drawColor(Color.BLACK);
                        for (int i = 0; i < values[0].length; i++) {
                                 int x=i;
                                 int downy=(int)(100-(values[0]<i>)*10);
                                 int upy=100;
                                 canvas.drawLine(x, downy, x, upy, paint);
 
                        }
                        imageView.invalidate();
                }
        }
 
        @Override
        public void onClick(View v) {
                started=true;
         new  RecordAudio().execute();
        }
 
}

android音频可视化的原理是使用离散傅里叶变换，但是数学不好的同学不要担心，有开源的java离散傅里叶变换的代码！！直接到www.netlib.org/fftpack/jfftpack.tgz，直接将里面javasource目录拖动到（ca目录）src即可！！