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audio/pcmconv: dithering

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This commit is contained in:
cinap_lenrek 2012-12-13 09:39:15 +01:00
parent a8b02eb198
commit d7b7723c96
1 changed files with 17 additions and 1 deletions
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18
sys/src/cmd/audio/pcmconv/pcmconv.c
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@ -141,7 +141,7 @@ filter(Chan *c)
} }
int* int*
resample(Chan *c, int *x, int *y, ulong count) resample(Chan *c, int *x, int *y, int count)
{ {
ulong e; ulong e;
int i, n; int i, n;
@ -196,6 +196,20 @@ resample(Chan *c, int *x, int *y, ulong count)
return y; return y;
} }
void
dither(int *y, int ibits, int obits, int count)
{
static ulong prnd;
if(ibits >= 32 || obits >= ibits)
return;
while(count--){
prnd = (prnd*0x19660dL + 0x3c6ef35fL) & 0xffffffffL;
*y++ += ((int)prnd) >> ibits;
}
}
void void
siconv(int *dst, uchar *src, int bits, int skip, int count) siconv(int *dst, uchar *src, int bits, int skip, int count)
{ {
@ -497,6 +511,7 @@ main(int argc, char *argv[])
l -= n; l -= n;
n /= i.framesz; n /= i.framesz;
(*iconv)(in, ibuf, i.bits, i.framesz, n); (*iconv)(in, ibuf, i.bits, i.framesz, n);
dither(in, i.bits, o.bits, n);
m = resample(&ch[0], in, out, n) - out; m = resample(&ch[0], in, out, n) - out;
if(m < 1){ if(m < 1){
if(n == 0) if(n == 0)
@ -506,6 +521,7 @@ main(int argc, char *argv[])
if(i.channels == o.channels){ if(i.channels == o.channels){
for(k=1; k<i.channels; k++){ for(k=1; k<i.channels; k++){
(*iconv)(in, ibuf + k*((i.bits+7)/8), i.bits, i.framesz, n); (*iconv)(in, ibuf + k*((i.bits+7)/8), i.bits, i.framesz, n);
dither(in, i.bits, o.bits, n);
resample(&ch[k], in, out, n); resample(&ch[k], in, out, n);
if(m > 0) if(m > 0)
(*oconv)(out, obuf + k*((o.bits+7)/8), o.bits, o.framesz, m); (*oconv)(out, obuf + k*((o.bits+7)/8), o.bits, o.framesz, m);