Conversion from u-law to PCM, 16 bit

Question

I am currently using two functions in my C source code to convert A-law files to PCM 16 bit and U-law files to PCM 16 bit. The conversion of U-law files to PCM 16 bit is not successfull. There is a lot of noise to the produced PCM 16 bit file.

Below there are the two functions:

short ALawToPcm16(char c)
{
    int i;
    short val;

    i = (c & 0x00FF) ^ 0x0055;

    if (i > 0x007F)
    {
        val = (short)(0x10000 - AIndexToPcm16Bit[i - 0x80]);
    }
    else
    {
        val = AIndexToPcm16Bit[i];
    }

    return(val);
}


short FctMuLawToPcm16(char c)
{
    int i;
    short val;

    i = (c & 0x00FF);

    if (i > 0x007F)
    {
        val = (short)(0x10000 - UIndexToPcm16Bit[i - 0x80]);
    }
    else
    {
        val = UIndexToPcm16Bit[i];
    }

    return(val);
}

Can anyone please tell me what is wrong with the second function? Thanks

Try replacing `i = (c & 0x00FF);` with `i = (c & 0x00FF) ^ 0x00FF;` — Ian Abbott, Dec 12 '16 at 12:34
Also, you might need to replace `val = (short)(0x10000 - UIndexToPcm16Bit[i - 0x80]);` with `val = (short)(0x10000 - UIndexToPcm16Bit[i - 0x80] - 1);` — Ian Abbott, Dec 12 '16 at 12:42
It worked by adding just the first comment in my source code. Thanks a lot! — A.Lap, Dec 13 '16 at 12:18

score 0 · Answer 1 · answered Sep 04 '18 at 09:26

0

Try replacing i = (c & 0x00FF); with i = (c & 0x00FF) ^ 0x00FF; – Ian Abbott

answered Sep 04 '18 at 09:26

Armali

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Conversion from u-law to PCM, 16 bit

1 Answers1