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round up vale calculated according to binary scaling depth

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This commit is contained in:
Robin P. Clark 2013-07-29 13:04:39 +01:00
parent 2db7cd7319
commit 3cce24f2f8
1 changed files with 7 additions and 2 deletions
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9
embedded_c_book/fo_filter/fo_filter.c
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@ -20,7 +20,7 @@ main()
{
int i;
INT16 var,fvar;
INT16 var,fvar, threeup_result;
var = ADRES;
@ -31,10 +31,11 @@ main()
naive_filter = (naive_filter * 7 + ADRES) / 8; // old filter
threeup_filter = (((threeup_filter << 3) - threeup_filter) >> 3) + ADRES;
threeup_result = (threeup_filter + 4)>>3;
fvar = filter16(var,3);
printf(" iteration: %d naive_filter = %x threeup_filter = %x fvar = %x fp = %lf\n", i, naive_filter, threeup_filter, fvar, fp);
printf(" iteration: %d naive_filter = %d threeup_filter = %d fvar = %d fp = %lf\n", i, naive_filter, threeup_result, fvar, fp);
}
}
@ -43,6 +44,8 @@ main()
#define BINARY_FILTER_SCALE 8
#define ROUND_UP ((1)<<(BINARY_FILTER_SCALE))
/* with BINARY_FILTER_SCALE set to 8, depth valid between 2 and 7 */
/* with a depth of 2 what we are saying is
* * result = (old_result * 3.0 + new_val ) / 4.0)
@ -59,6 +62,8 @@ INT16 filter16(INT16 var, int depth)
v <<= BINARY_FILTER_SCALE; // scale up
printf(" v = %lx : ", v);
v2 = (oldv << depth) - oldv + v;
// now round-up
v2 += ROUND_UP;
v2 >>= depth;
oldv = v2;
printf(" v = %lx oldv = %lx ", v, oldv);