[問題] FFT

看板C_and_CPP (C/C++)作者weast (kuan)時間16年前 (2009/03/29 19:14)推噓3(3推 0噓 7→)

留言10則, 5人參與討論串2/2 (看更多)

我這邊有一段FFT程式可是他規定是只能用256點去跑請問各位有沒有辦法再這段程式的基礎上改成可以給定任意點呢? void FFT(double *segment, double **X) { int M = 8 , iN = Dim; int i, j, k, limit_1, limit_2, limit_3, ij, il; double farg, fpi = 3.1415926, fCos, fSin, fbr, fbi, fcr, fci, fx1, fx2; double *fxr = new double[window + 1]; double *fxi = new double[window + 1]; //****************** 將segment[256] => fxr[window] *************// for (i = 1; i <= window; i++) fxr[i] = fxi[i] = 0; //初始化fxr[window], fxi[window] for (i = 1; i <= window; i++) fxr[i] = segment[i - 1]; //將原始信號的256點個值 => fxr[window] // ***************** 傅立葉主程式開始 *************// limit_1 = iN - 1; limit_2 = iN / 2; ij = 1; // **************** 重排輸入值 ************// for (i = 1; i <= limit_1; i++) { if ((float) i <= ((float) ij - 0.01)) { fx1 = fxr[ij]; fx2 = fxi[ij]; fxr[ij] = fxr[i]; fxi[ij] = fxi[i]; fxr[i] = fx1; fxi[i] = fx2; } il = limit_2; while(1) { if ((float)il > ((float) (ij) - 0.01)) break; ij -= il; il /=2; } ij += il; } // **************** 傅立葉轉換 *************** // for(i = 1; i <= M; i++) // (limit_1, limit_2) =>(1, 256) (2, 128) (4, 64) (8, 32)..(256,1) { limit_1 = (int) pow(2, i - 1); limit_2 = (int) pow(2, (M - i)); for(j = 1; j <= limit_2; j++) //(1:256) (1:128) (1:64)..........(1:1) { for (k = 1; k <= limit_1; k++) { limit_3 = (k - 1) + (j - 1) * 2 * limit_1 + 1; //Odd Points //******************* fbr = fxr[limit_3]; fbi = fxi[limit_3]; fcr = fxr[limit_3 + limit_1]; fci = fxi[limit_3 + limit_1]; //******************* farg = 2.0 * fpi * (k - 1) * limit_2 / iN; fCos = cosl (farg); fSin = sinl (farg); //******************* fx1 = fcr * fCos + fci * fSin ; fx2 = fci * fCos + (0 - fcr) * fSin ; // fxr[limit_3] = fbr + fx1; fxi[limit_3] = fbi + fx2; fxr[limit_3 + limit_1] = fbr - fx1; fxi[limit_3 + limit_1] = fbi - fx2; } } } // for (i = 1; i <= window; i++) { X[0][i - 1] = fxr[i]; X[1][i - 1] = fxi[i]; } //cout << "X[] = " << X[0][0]; delete[] fxr, fxi; } 謝謝各位了!! -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.120.90.193