Hi,

I'm trying to get meaningful voice from ALSA buffer. I read tutorial on http://www.suse.de/~mana/alsa090_howto.htmlhttp://www.suse.de/%7Emana/alsa090_howto.htmland realize that if alsa use 16 bit format value then I have to byte shift to store it in 8 bit unsigned char buffer. I see this in sine wave generator in tutorial. To confirm it, I try to save the output into file and open it in Matlab. I want to know if this is correct, because when I try saving alsa buffer on a from recording I still get noise not the voice.

Thank you.

Best regards,

Arif

This is my implementation :

int main() { int nchannel = 1; int periodsize = 8192; int frame_size = nchannel * (16 / 8); int num_frames = periodsize / frame_size;

unsigned char *data; int l2; short s;

data = (unsigned char *)malloc(periodsize);

// fill the buffer for(l2 = 0; l2 < num_frames; l2++) { s1 = (l2 % 128) * 100 - 5000; data[2*l2] = (unsigned char)s1; data[2*l2+1] = s1 >> 8; }

// directly save FILE *fp1 = fopen("sineout1", "w");

for (int i = 0; i < periodsize; i++) { fprintf_s(fp1, "%d\n", data[i]); }

fclose(fp1);

// with bit shifting from char to short FILE *fp2 = fopen("sineout2", "w");

for (int i = 0; i < num_frames; i++) { short newval = data[2*i+1] << 8; newval += data[2*i];

fprintf_s(fp2, "%d\n", newval); }

fclose(fp2);

return 0; }