Android G711A编解码

封装G711类：

public class G711 {
    private static short aLawDecompressTable[] = new short[] { -5504, -5248,
            -6016, -5760, -4480, -4224, -4992, -4736, -7552, -7296, -8064,
            -7808, -6528, -6272, -7040, -6784, -2752, -2624, -3008, -2880,
            -2240, -2112, -2496, -2368, -3776, -3648, -4032, -3904, -3264,
            -3136, -3520, -3392, -22016, -20992, -24064, -23040, -17920,
            -16896, -19968, -18944, -30208, -29184, -32256, -31232, -26112,
            -25088, -28160, -27136, -11008, -10496, -12032, -11520, -8960,
            -8448, -9984, -9472, -15104, -14592, -16128, -15616, -13056,
            -12544, -14080, -13568, -344, -328, -376, -360, -280, -264, -312,
            -296, -472, -456, -504, -488, -408, -392, -440, -424, -88, -72,
            -120, -104, -24, -8, -56, -40, -216, -200, -248, -232, -152, -136,
            -184, -168, -1376, -1312, -1504, -1440, -1120, -1056, -1248, -1184,
            -1888, -1824, -2016, -1952, -1632, -1568, -1760, -1696, -688, -656,
            -752, -720, -560, -528, -624, -592, -944, -912, -1008, -976, -816,
            -784, -880, -848, 5504, 5248, 6016, 5760, 4480, 4224, 4992, 4736,
            7552, 7296, 8064, 7808, 6528, 6272, 7040, 6784, 2752, 2624, 3008,
            2880, 2240, 2112, 2496, 2368, 3776, 3648, 4032, 3904, 3264, 3136,
            3520, 3392, 22016, 20992, 24064, 23040, 17920, 16896, 19968, 18944,
            30208, 29184, 32256, 31232, 26112, 25088, 28160, 27136, 11008,
            10496, 12032, 11520, 8960, 8448, 9984, 9472, 15104, 14592, 16128,
            15616, 13056, 12544, 14080, 13568, 344, 328, 376, 360, 280, 264,
            312, 296, 472, 456, 504, 488, 408, 392, 440, 424, 88, 72, 120, 104,
            24, 8, 56, 40, 216, 200, 248, 232, 152, 136, 184, 168, 1376, 1312,
            1504, 1440, 1120, 1056, 1248, 1184, 1888, 1824, 2016, 1952, 1632,
            1568, 1760, 1696, 688, 656, 752, 720, 560, 528, 624, 592, 944, 912,
            1008, 976, 816, 784, 880, 848 };

    private final static int cClip = 32635;
    private static byte aLawCompressTable[] = new byte[] { 1, 1, 2, 2, 3, 3, 3,
            3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
            5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7 };

    public static int encode(byte[] src, int offset, int len, byte[] res) {
        int j = offset;
        int count = len / 2;
        short sample = 0;

        for (int i = 0; i < count; i++) {
            sample = (short) (((src[j++] & 0xff) | (src[j++]) << 8));
            res[i] = linearToALawSample(sample);
        }
        return count;
    }

    private static byte linearToALawSample(short sample) {
        int sign;
        int exponent;
        int mantissa;
        int s;

        sign = ((~sample) >> 8) & 0x80;
        if (!(sign == 0x80)) {
            sample = (short) -sample;
        }
        if (sample > cClip) {
            sample = cClip;
        }
        if (sample >= 256) {
            exponent = (int) aLawCompressTable[(sample >> 8) & 0x7F];
            mantissa = (sample >> (exponent + 3)) & 0x0F;
            s = (exponent << 4) | mantissa;
        } else {
            s = sample >> 4;
        }
        s ^= (sign ^ 0x55);
        return (byte) s;
    }

    public static int decode(byte[] src, int offset, int len, byte[] res) {
        int j = 0;
        for (int i = 0; i < len; i++) {
            short s = aLawDecompressTable[src[i + offset] & 0xff];
            res[j++] = (byte) s;
            res[j++] = (byte) (s >> 8);
        }
        return j;
    }

 

说明:

G711.encode(byte[] src, int offset, int len, byte[] res);

byte[] src 为编码前的数据   offset偏移量 len 长度   byte[] res为编码后存放的数据

编码后res数组长度应为编码前src数组长度的一半

例：

byte[] outbuf = new byte[src.length / 2];
int encodeSize = G711.encode(src, 0, src.length, outbuf);

 

G711.decode(byte[] src, int offset, int len, byte[] res)；

byte[] src 为解码前的数据  offset偏移量 len 长度  byte[] res为解码后存放的数据

解码后res数组长度应为解码前src数组长度的两倍

例：

byte[] outbuf = new byte[src.length * 2];
int encodeSize = G711.decode(src, 0, src.length, outbuf);

 

参考：

https://blog.csdn.net/devil__lee/article/details/39897661

https://blog.csdn.net/qq_24551315/article/details/51134689