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add a "low-pass filter"

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Eric Wasylishen 2011-12-27 23:18:00 -07:00
parent 3230c48375
commit 97f7bd902e
1 changed files with 40 additions and 8 deletions
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48
Quake/snd_mem.c
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@ -22,7 +22,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#include "quakedef.h"
static int getsample(byte *data, int inwidth, int srcsample)
static int getsamplefromfile(byte *data, int inwidth, int srcsample)
{
if (inwidth == 2)
return LittleShort ( ((short *)data)[srcsample] );
@ -30,6 +30,14 @@ static int getsample(byte *data, int inwidth, int srcsample)
return (int)( (unsigned char)(data[srcsample]) - 128) << 8;
}
static int getsample(byte *data, int inwidth, int srcsample)
{
if (inwidth == 2)
return ((short *)data)[srcsample];
else
return (int)(((signed char *)data)[srcsample]) << 8;
}
static void putsample(byte *data, int outwidth, int i, int sample)
{
if (outwidth == 2)
@ -87,22 +95,46 @@ static void ResampleSfx (sfx_t *sfx, int inrate, int inwidth, byte *data)
for (i = 0, samplefrac = 0; i < outcount; i++, samplefrac += stepscale)
{
int srcsample1 = CLAMP(0, floor(samplefrac), incount - 1);
int srcsample2 = CLAMP(0, ceil(samplefrac), incount - 1);
int srcsample2 = CLAMP(0, ceil(samplefrac), incount - 1);
float srcsample2weight = samplefrac - floor(samplefrac);
float srcsample1weight = 1 - srcsample2weight;
sample = (srcsample1weight * getsample(data, inwidth, srcsample1))
+ (srcsample2weight * getsample(data, inwidth, srcsample2));
// how far between the samples. in [0, 1].
float mu = samplefrac - floor(samplefrac);
float srcsample1weight = 1 - mu;
float srcsample2weight = mu;
sample = (srcsample1weight * getsamplefromfile(data, inwidth, srcsample1))
+ (srcsample2weight * getsamplefromfile(data, inwidth, srcsample2));
putsample(sc->data, sc->width, i, sample);
}
// poor man's low pass filter:
// s[i] = (s[i] + s[i+1] + s[i+2] + s[i+3]) / 4
const int avg = 4;
char temp[sc->width * sc->length];
memset(temp, 0, sc->width * sc->length);
for (i = 0; i < outcount; i++)
{
int64_t sum = 0;
int j;
for (j=0; j<avg; j++)
{
int pos = CLAMP(0, i + j, outcount - 1);
sum += getsample(sc->data, sc->width, pos);
}
sum /= avg;
putsample(temp, sc->width, i, sum);
}
memcpy(sc->data, temp, sc->width * sc->length);
}
else
{
// general case / downsampling
for (i = 0, samplefrac = 0; i < outcount; i++, samplefrac += stepscale)
{
sample = getsample(data, inwidth, (int)samplefrac);
sample = getsamplefromfile(data, inwidth, (int)samplefrac);
putsample(sc->data, sc->width, i, sample);
}
}