| Line 22... |
Line 22... |
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// for more details.
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//
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//
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// You should have received a copy of the GNU General Public License along
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// You should have received a copy of the GNU General Public License along
|
// with this program. (It's in the $(ROOT)/doc directory, run make with no
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// with this program. (It's in the $(ROOT)/doc directory. Run make with no
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// target there if the PDF file isn't present.) If not, see
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// target there if the PDF file isn't present.) If not, see
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// <http://www.gnu.org/licenses/> for a copy.
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// <http://www.gnu.org/licenses/> for a copy.
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//
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//
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// License: GPL, v3, as defined and found on www.gnu.org,
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// License: GPL, v3, as defined and found on www.gnu.org,
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// http://www.gnu.org/licenses/gpl.html
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// http://www.gnu.org/licenses/gpl.html
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| Line 118... |
Line 118... |
// For an FFT stage of 2^n elements, we need 2^(n-1) butterfly
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// For an FFT stage of 2^n elements, we need 2^(n-1) butterfly
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// coefficients, sometimes called twiddle factors. Stage captures the
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// coefficients, sometimes called twiddle factors. Stage captures the
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// width of the FFT at this point. If thiss is a 2x at a time FFT,
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// width of the FFT at this point. If thiss is a 2x at a time FFT,
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// nwide will be equal to 2, and offset will be one or two.
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// nwide will be equal to 2, and offset will be one or two.
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//
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//
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assert(nwide > 0);
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// assert(nwide > 0);
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assert(offset < nwide);
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// assert(offset < nwide);
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assert(stage / nwide > 1);
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// assert(stage / nwide > 1);
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assert(stage % nwide == 0);
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// assert(stage % nwide == 0);
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printf("GEN-COEFFS(): stage =%4d, bits =%2d, nwide = %d, offset = %d, nverse = %d\n", stage, cbits, nwide, offset, inv);
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// printf("GEN-COEFFS(): stage =%4d, bits =%2d, nwide = %d, offset = %d, nverse = %d\n", stage, cbits, nwide, offset, inv);
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int ncoeffs = stage/nwide/2;
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int ncoeffs = stage/nwide/2;
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for(int i=0; i<ncoeffs; i++) {
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for(int i=0; i<ncoeffs; i++) {
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int k = nwide*i+offset;
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int k = nwide*i+offset;
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double W = ((inv)?1:-1)*2.0*M_PI*k/(double)(stage);
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double W = ((inv)?1:-1)*2.0*M_PI*k/(double)(stage);
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double c, s;
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double c, s;
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