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swr: add triangular highpass dither 

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);
}

1
libswresample/swresample.c
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@ -56,6 +56,7 @@ static const AVOption options[]={
{"dither", "dither method" , OFFSET(dither_method), AV_OPT_TYPE_INT, {.dbl=0}, 0, SWR_DITHER_NB-1, 0, "dither_method"},
{"rectangular", "rectangular dither", 0, AV_OPT_TYPE_CONST, {.dbl=SWR_DITHER_RECTANGULAR}, INT_MIN, INT_MAX, 0, "dither_method"},
{"triangular" , "triangular dither" , 0, AV_OPT_TYPE_CONST, {.dbl=SWR_DITHER_TRIANGULAR }, INT_MIN, INT_MAX, 0, "dither_method"},
{"triangular_hp" , "triangular dither with high pass" , 0, AV_OPT_TYPE_CONST, {.dbl=SWR_DITHER_TRIANGULAR_HIGHPASS }, INT_MIN, INT_MAX, 0, "dither_method"},
{0}
};

1
libswresample/swresample.h
View File

@ -49,6 +49,7 @@ enum SwrDitherType {
SWR_DITHER_NONE = 0,
SWR_DITHER_RECTANGULAR,
SWR_DITHER_TRIANGULAR,
SWR_DITHER_TRIANGULAR_HIGHPASS,
SWR_DITHER_NB, ///< not part of API/ABI
};