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fix whitespace

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This commit is contained in:
Jörg Thalheim 2015-03-02 23:42:03 +01:00
parent 19d397b237
commit 907005f752
4 changed files with 16 additions and 28 deletions
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36
fft-org.c
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@ -3,16 +3,16 @@
fix_fft() perform FFT or inverse FFT
fix_mpy() perform fixed-point multiplication.
Sinewave[1024] sinewave normalized to 32767 (= 1.0).
All data are fixed-point short integers, in which
-32768 to +32768 represent -1.0 to +1.0. Integer arithmetic
is used for speed, instead of the more natural floating-point.
For the forward FFT (time -> freq), fixed scaling is
performed to prevent arithmetic overflow, and to map a 0dB
sine/cosine wave (i.e. amplitude = 32767) to two -6dB freq
coefficients; the one in the lower half is reported as 0dB.
For the inverse FFT (freq -> time), fixed scaling cannot be
done, as two 0dB coefficients would sum to a peak amplitude of
64K, overflowing the 32k range of the fixed-point integers.
@ -44,11 +44,11 @@
int fix_fft_org(fixed fr[], fixed fi[], int m, int inverse)
{
int mr,nn,i,j,l,k,istep, n, scale, shift;
fixed qr,qi; //even input
fixed tr,ti; //odd input
fixed wr,wi; //twiddle factor
//number of input data
n = 1<<m;
@ -70,13 +70,13 @@ int fix_fft_org(fixed fr[], fixed fi[], int m, int inverse)
tr = fr[m];
fr[m] = fr[mr];
fr[mr] = tr;
ti = fi[m];
fi[m] = fi[mr];
fi[mr] = ti;
}
l = 1;
k = LOG2_N_WAVE-1;
while(l < n)
@ -89,10 +89,10 @@ int fix_fft_org(fixed fr[], fixed fi[], int m, int inverse)
{
j = fr[i];
if(j < 0) j = -j;
m = fi[i];
if(m < 0) m = -m;
if(j > 16383 || m > 16383)
{
shift = 1;
@ -109,7 +109,7 @@ int fix_fft_org(fixed fr[], fixed fi[], int m, int inverse)
distributed to maximize arithmetic accuracy. */
shift = 1;
}
/* it may not be obvious, but the shift will be performed
on each data point exactly once, during this pass. */
istep = l << 1; //step width of current butterfly
@ -119,7 +119,7 @@ int fix_fft_org(fixed fr[], fixed fi[], int m, int inverse)
/* 0 <= j < N_WAVE/2 */
wr = Sinewave[j+N_WAVE/4];
wi = -Sinewave[j];
if(inverse) wi = -wi;
if(shift)
{
@ -128,20 +128,20 @@ int fix_fft_org(fixed fr[], fixed fi[], int m, int inverse)
}
for(i=m; i<n; i+=istep)
{
j = i + l;
tr = fix_mpy(wr,fr[j]) - fix_mpy(wi,fi[j]);
ti = fix_mpy(wr,fi[j]) + fix_mpy(wi,fr[j]);
qr = fr[i];
qi = fi[i];
if(shift)
{
qr >>= 1;
qi >>= 1;
}
fr[j] = qr - tr;
fi[j] = qi - ti;
fr[i] = qr + tr;
@ -300,7 +300,3 @@ fixed Sinewave_org[1024] = {
-3211, -3011, -2811, -2610, -2410, -2209, -2009, -1808,
-1607, -1406, -1206, -1005, -804, -603, -402, -201,
};

2
fft-org.h
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@ -1,4 +1,3 @@
#ifndef FFT_H
#define FFT_H
@ -22,5 +21,4 @@ extern fixed Sinewave_org[N_WAVE];
fixed fix_mpy_org(fixed a, fixed b);
int fix_fft_org(fixed *fr, fixed *fi, int m, int inverse);
#endif //FFT_H

4
fft.c
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@ -300,7 +300,3 @@ fixed Sinewave[1024] = {
-3211, -3011, -2811, -2610, -2410, -2209, -2009, -1808,
-1607, -1406, -1206, -1005, -804, -603, -402, -201,
};

2
fft.h
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@ -1,4 +1,3 @@
#ifndef FFT_H
#define FFT_H
@ -22,5 +21,4 @@ extern fixed Sinewave[N_WAVE];
fixed fix_mpy(fixed a, fixed b);
int fix_fft(fixed *fr, fixed *fi, int m, int inverse);
#endif //FFT_H