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fixed shifting of filter history in fifth_order() 

fifth_order() filters and decimates by two, and therefore always shifts
by two input samples for every output sample. However, for the first
output sample, it shifted the state from the previous call to
fifth_order() by only one input sample, and it never used the last
sample in its input buffer.
pull/12/head
Vincent Arkesteijn 2017-04-27 15:08:35 +02:00
rodzic 0b456b52e0
commit a2a8e7818c
1 zmienionych plików z 8 dodań i 8 usunięć
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rtl_ais.c
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@ -154,12 +154,12 @@ static void fifth_order(int16_t *data, int length, int16_t *hist)
{
int i;
int16_t a, b, c, d, e, f;
a = hist[1];
b = hist[2];
c = hist[3];
d = hist[4];
e = hist[5];
f = data[0];
a = hist[2];
b = hist[3];
c = hist[4];
d = hist[5];
e = data[0];
f = data[2];
/* a downsample should improve resolution, so don't fully shift */
data[0] = (a + (b+e)*5 + (c+d)*10 + f) >> 4;
for (i=4; i<length; i+=4) {
@ -167,8 +167,8 @@ static void fifth_order(int16_t *data, int length, int16_t *hist)
b = d;
c = e;
d = f;
e = data[i-2];
f = data[i];
e = data[i];
f = data[i+2];
data[i/2] = (a + (b+e)*5 + (c+d)*10 + f) >> 4;
}
/* archive */