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swr: add triangular highpass dither

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Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer
2012-04-11 13:27:22 +02:00
parent 1fc4ff2205
commit f8a237a307
3 changed files with 24 additions and 1 deletions
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23
libswresample/dither.c
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@@ -23,6 +23,8 @@
void swri_get_dither(void *dst, int len, unsigned seed, enum AVSampleFormat out_fmt, enum AVSampleFormat in_fmt, enum SwrDitherType method) {
double scale = 0;
#define TMP_EXTRA 2
double *tmp = av_malloc((len + TMP_EXTRA) * sizeof(double));
int i;
if(in_fmt == AV_SAMPLE_FMT_FLT || in_fmt == AV_SAMPLE_FMT_DBL){
@@ -34,19 +36,36 @@ void swri_get_dither(void *dst, int len, unsigned seed, enum AVSampleFormat out_
if(in_fmt == AV_SAMPLE_FMT_S32 && out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1L<<24;
if(in_fmt == AV_SAMPLE_FMT_S16 && out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1L<<8;
for(i=0; i<len; i++){
for(i=0; i<len + TMP_EXTRA; i++){
double v;
seed = seed* 1664525 + 1013904223;
switch(method){
case SWR_DITHER_RECTANGULAR: v= ((double)seed) / UINT_MAX - 0.5; break;
case SWR_DITHER_TRIANGULAR :
case SWR_DITHER_TRIANGULAR_HIGHPASS :
v = ((double)seed) / UINT_MAX;
seed = seed*1664525 + 1013904223;
v-= ((double)seed) / UINT_MAX;
break;
default: av_assert0(0);
}
tmp[i] = v;
}
for(i=0; i<len; i++){
double v;
switch(method){
case SWR_DITHER_RECTANGULAR:
case SWR_DITHER_TRIANGULAR :
v = tmp[i];
break;
case SWR_DITHER_TRIANGULAR_HIGHPASS :
v = (- tmp[i] + 2*tmp[i+1] - tmp[i+2]) / sqrt(6);
break;
default: av_assert0(0);
}
v*= scale;
@@ -58,4 +77,6 @@ void swri_get_dither(void *dst, int len, unsigned seed, enum AVSampleFormat out_
default: av_assert0(0);
}
}
av_free(tmp);
}