android - 音频滤波器算法

Question

我想通过修改字节将过滤器添加到音频文件(.wav)，但我遇到的问题是声音有噪音。

public class MainActivity extends ActionBarActivity {
    private int bufferSize = 0;
    private static final int RECORDER_BPP = 16;
    private static final String AUDIO_RECORDER_FILE_EXT_WAV = ".wav";
    private static final String AUDIO_RECORDER_FOLDER = "ks";

    private static final int RECORDER_SAMPLERATE = 44100;
    private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_STEREO;
    private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bufferSize = AudioRecord.getMinBufferSize(RECORDER_SAMPLERATE,
                RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING);

        String file1 = "/storage/emulated/0/File/rec.wav";
        String file2 = "/storage/emulated/0/File/rec2.wav";
        copyWaveFile(file1,file2);
    }

    static final float ALPHA = 0.15f;

    private float[] lowPass(float[] input, float[] output) {
        if (output == null)
            return input;


        for (int n = 0; n < input.length; n++) {
            output[n] = output[n] + ALPHA * (input[n] - output[n]);
        }
        return output;

    }

    private static float[] toFloatArray(byte[] buffer) {
        ByteArrayInputStream bas = new ByteArrayInputStream(buffer);
        DataInputStream ds = new DataInputStream(bas);
        float[] fArr = new float[buffer.length / 4]; // 4 bytes per float
        for (int i = 0; i < fArr.length; i++) {
            try {
                fArr[i] = ds.readFloat();
            } catch (IOException e) {
                Log.e("E", "eRRO :" + e.getMessage());
                e.printStackTrace();
            }
        }
        return fArr;
    }

    private static byte[] toByteArray(float[] fArr) {
        ByteArrayOutputStream bas = new ByteArrayOutputStream();
        DataOutputStream ds = new DataOutputStream(bas);
        for (float f : fArr)
            try {
                ds.writeFloat(f);
            } catch (IOException e) {
                Log.i("", "ERROR:" + e.getMessage());
                e.printStackTrace();
            }
        byte[] bytes = bas.toByteArray();

        return bytes;
    }

    private void copyWaveFile(String file1, String file2) {
        FileInputStream in1 = null;
        FileOutputStream out = null;
        long totalAudioLen = 0;
        long totalDataLen = totalAudioLen + 36;
        long longSampleRate = RECORDER_SAMPLERATE;
        int channels = 2;
        long byteRate = RECORDER_BPP * RECORDER_SAMPLERATE * channels / 8;

        byte[] data = new byte[bufferSize];
        byte[] dataOut = new byte[bufferSize];
        float[] floatArray = null;
        try {
            in1 = new FileInputStream(file1);
            out = new FileOutputStream(file2);

            totalAudioLen = in1.getChannel().size();
            totalDataLen = totalAudioLen + 36;

            WriteWaveFileHeader(out, totalAudioLen, totalDataLen,
                    longSampleRate, channels, byteRate);

            while (in1.read(data) != -1) {

                floatArray = lowPass(toFloatArray(data), toFloatArray(dataOut));
                // out.write(data); original 
                out.write(toByteArray(floatArray));
            }

            out.close();
            in1.close();

            Toast.makeText(this, "Done!!", Toast.LENGTH_LONG).show();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void WriteWaveFileHeader(FileOutputStream out, long totalAudioLen,
            long totalDataLen, long longSampleRate, int channels, long byteRate)
            throws IOException {

        byte[] header = new byte[44];

        header[0] = 'R'; // RIFF/WAVE header
        header[1] = 'I';
        header[2] = 'F';
        header[3] = 'F';
        header[4] = (byte) (totalDataLen & 0xff);
        header[5] = (byte) ((totalDataLen >> 8) & 0xff);
        header[6] = (byte) ((totalDataLen >> 16) & 0xff);
        header[7] = (byte) ((totalDataLen >> 24) & 0xff);
        header[8] = 'W';
        header[9] = 'A';
        header[10] = 'V';
        header[11] = 'E';
        header[12] = 'f'; // 'fmt ' chunk
        header[13] = 'm';
        header[14] = 't';
        header[15] = ' ';
        header[16] = 16; // 4 bytes: size of 'fmt ' chunk
        header[17] = 0;
        header[18] = 0;
        header[19] = 0;
        header[20] = 1; // format = 1
        header[21] = 0;
        header[22] = (byte) channels;
        header[23] = 0;
        header[24] = (byte) (longSampleRate & 0xff);
        header[25] = (byte) ((longSampleRate >> 8) & 0xff);
        header[26] = (byte) ((longSampleRate >> 16) & 0xff);
        header[27] = (byte) ((longSampleRate >> 24) & 0xff);
        header[28] = (byte) (byteRate & 0xff);
        header[29] = (byte) ((byteRate >> 8) & 0xff);
        header[30] = (byte) ((byteRate >> 16) & 0xff);
        header[31] = (byte) ((byteRate >> 24) & 0xff);
        header[32] = (byte) (2 * 16 / 8); // block align
        header[33] = 0;
        header[34] = RECORDER_BPP; // bits per sample
        header[35] = 0;
        header[36] = 'd';
        header[37] = 'a';
        header[38] = 't';
        header[39] = 'a';
        header[40] = (byte) (totalAudioLen & 0xff);
        header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
        header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
        header[43] = (byte) ((totalAudioLen >> 24) & 0xff);

        out.write(header, 0, 44);
    }
}

有人可以帮助我解决奇怪的声音，以及如何获得更多音频滤波器算法并实现。

Answer 1

您可以尝试使用Matlab查看波的类型以及噪声存在的频率。然后可以设计低通滤波器，使截止频率位于噪声的边界。