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make the box filter work in-place (O(box-width) memory instead of O(sound-length) memory)

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Eric Wasylishen 2011-12-28 21:39:31 -07:00
parent 7e56c24345
commit aedfb9636d
1 changed files with 23 additions and 12 deletions
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35
Quake/snd_mem.c
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@ -113,25 +113,36 @@ static void ResampleSfx (sfx_t *sfx, int inrate, int inwidth, byte *data)
putsample(sc->data, sc->width, i, sample);
}
// poor man's low pass filter:
// box filter
// FIXME: doesn't handle the start or end of the sound properly
const int avg = 4;
char temp[sc->width * sc->length];
memset(temp, 0, sc->width * sc->length);
const int left = 2;
const int right = 2;
const int box_width = left + right + 1;
int history[left];
memset(history, 0, sizeof(history));
int box_sum = 0;
for (i = 0; i < outcount; i++)
{
int64_t sum = 0;
const int sample_at_i = getsample(sc->data, sc->width, i);
box_sum += sample_at_i;
box_sum -= history[0];
const int newsample = box_sum / box_width;
const int write_loc = CLAMP(0, i - right, outcount - 1);
// before writing the sample at write_loc, copy it to the end of the history buffer
int j;
for (j = (i-(avg/2)); j < (i-(avg/2)) + avg; j++)
for (j=0; j<(left-1); j++)
{
int pos = CLAMP(0, j, outcount - 1);
sum += getsample(sc->data, sc->width, pos);
history[j] = history[j+1];
}
sum /= avg;
putsample(temp, sc->width, i, sum);
history[left-1] = getsample(sc->data, sc->width, write_loc);
putsample(sc->data, sc->width, write_loc, newsample);
}
memcpy(sc->data, temp, sc->width * sc->length);
}
else
{