AudioRecord的raw转8位wav或mp3

AudioRecord在android设备8位是不一样支持，对于有时需要和其他设备进行传输(只能接受8位)也为了压缩等问题，不得不把16位的原数据进行转换。

AudioRecord的具体使用办法就不粘出来了，度娘那里有不少。

1.16位数据转8位数据 这里得到8位wav

public void copyWaveFile() {

File file = new File(AudioName);

if (!file.exists()) {

return;

}

long totalAudioLen = 0;

long totalDataLen = totalAudioLen + 36;

long longSampleRate = frequence;

int channels = 1;

long byteRate = 8 * frequence * channels / 8;

try {

int dateLength = (int) (file.length() / 2);

short[] data = new short[dateLength];

byte[] Bytedata=new byte[dateLength];

InputStream is = new FileInputStream(file);

BufferedInputStream bis = new BufferedInputStream(is);

DataInputStream dis = new DataInputStream(bis);

FileOutputStream out = new FileOutputStream(NewAudioName);

totalAudioLen = dateLength;

totalDataLen = totalAudioLen + 36;

WriteWaveFileHeader(out, totalAudioLen, totalDataLen,

longSampleRate, channels, byteRate);

int size=0;

int i = 0;

while (dis.available() > 0) {

data = dis.readShort();

// 16位转8位 保留前八位 第一位取反

if (data > 0x8000) {

Bytedata = (byte) (0x80 - (0xff - data >> 8));

} else {

Bytedata = (byte) (0x80 + (data>> 8));

}

i++;

}

out.write(Bytedata);

dis.close();

out.close();

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* 8位的wav文件头 这里提供一个头信息。插入这些信息就可以得到可以播放的文件。每种格式的文件都有自己特有的头文件。

*/

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) (1 * 8 / 8); // block align

header[33] = 0;

header[34] = 8; // 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);

}

2.转换成MP3,是将lame移植到android上，这里用了别人打包好了的[使用Lame把音频文件转换成mp3格式](http://www.pocketdigi.com/20130306/996.html)，里面有附带移植方法链接以及第三方包使用方法。这里转换成MP3

public void writeMP3() {

File file = new File(AudioName);

if (!file.exists()) {

return;

}

FLameUtils lameUtils = new FLameUtils(1, frequence, 96);

lameUtils.raw2mp3(AudioName, MP3Name);

}

3.频谱，用到了FFT 快速傅里叶变换

public void fft(Complex[] xin, int N) {

int f, m, N2, nm, i, k, j, L;// L:运算级数

float p;

int e2, le, B, ip;

Complex w = new Complex();

Complex t = new Complex();

N2 = N / 2;// 每一级中蝶形的个数,同时也代表m位二进制数最高位的十进制权值

f = N;// f是为了求流程的级数而设立的

for (m = 1; (f = f / 2) != 1; m++)

; // 得到流程图的共几级

nm = N - 2;

j = N2;

/****** 倒序运算——雷德算法 ******/

for (i = 1; i <= nm; i++) {

if (i < j)// 防止重复交换

{

t = xin[j];

xin[j] = xin;

xin = t;

}

k = N2;

while (j >= k) {

j = j - k;

k = k / 2;

}

j = j + k;

}

/****** 蝶形图计算部分 ******/

for (L = 1; L <= m; L++) // 从第1级到第m级

{

e2 = (int) Math.pow(2, L);

// e2=(int)2.pow(L);

le = e2 + 1;

B = e2 / 2;

for (j = 0; j < B; j++) // j从0到2^(L-1)-1

{

p = 2 * pi / e2;

w.real = Math.cos(p * j);

// w.real=Math.cos((double)p*j); //系数W

w.image = Math.sin(p * j) * -1;

// w.imag = -sin(p*j);

for (i = j; i < N; i = i + e2) // 计算具有相同系数的数据

{

ip = i + B; // 对应蝶形的数据间隔为2^(L-1)

t = xin[ip].cc(w);

xin[ip] = xin.cut(t);

xin = xin.sum(t);

}

}

}

}