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avcodec/rdft: reorder calculation

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old:
 165188 decicycles in  rdft,   65536 runs,      0 skips
 165865 decicycles in irdft,   65536 runs,      0 skips
new:
 142487 decicycles in  rdft,   65536 runs,      0 skips
 141498 decicycles in irdft,   65536 runs,      0 skips

Signed-off-by: Muhammad Faiz <mfcc64@gmail.com>
This commit is contained in:
Muhammad Faiz 2017-07-22 06:52:45 +07:00
parent 7140761481
commit c8305079da
1 changed files with 8 additions and 6 deletions
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14
libavcodec/rdft.c
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@ -35,7 +35,7 @@
static void rdft_calc_c(RDFTContext *s, FFTSample *data)
{
int i, i1, i2;
FFTComplex ev, od;
FFTComplex ev, od, odsum;
const int n = 1 << s->nbits;
const float k1 = 0.5;
const float k2 = 0.5 - s->inverse;
@ -58,14 +58,16 @@ static void rdft_calc_c(RDFTContext *s, FFTSample *data)
i2 = n-i1; \
/* Separate even and odd FFTs */ \
ev.re = k1*(data[i1 ]+data[i2 ]); \
od.im = -k2*(data[i1 ]-data[i2 ]); \
od.im = k2*(data[i2 ]-data[i1 ]); \
ev.im = k1*(data[i1+1]-data[i2+1]); \
od.re = k2*(data[i1+1]+data[i2+1]); \
/* Apply twiddle factors to the odd FFT and add to the even FFT */ \
data[i1 ] = ev.re + od.re*tcos[i] sign0 od.im*tsin[i]; \
data[i1+1] = ev.im + od.im*tcos[i] sign1 od.re*tsin[i]; \
data[i2 ] = ev.re - od.re*tcos[i] sign1 od.im*tsin[i]; \
data[i2+1] = -ev.im + od.im*tcos[i] sign1 od.re*tsin[i]; \
odsum.re = od.re*tcos[i] sign0 od.im*tsin[i]; \
odsum.im = od.im*tcos[i] sign1 od.re*tsin[i]; \
data[i1 ] = ev.re + odsum.re; \
data[i1+1] = ev.im + odsum.im; \
data[i2 ] = ev.re - odsum.re; \
data[i2+1] = odsum.im - ev.im; \
}
if (s->negative_sin) {