/*____________________________________________________________________________ FreeAmp - The Free MP3 Player MP3 Decoder originally Copyright (C) 1995-1997 Xing Technology Corp. http://www.xingtech.com Portions Copyright (C) 1998-1999 EMusic.com This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. $Id: mdct.c,v 1.4 1999/10/19 07:13:09 elrod Exp $ ____________________________________________________________________________*/ /**** mdct.c *************************************************** Layer III cos transform for n=18, n=6 computes c[k] = Sum( cos((pi/4*n)*(2*k+1)*(2*p+1))*f[p] ) k = 0, ...n-1, p = 0...n-1 inplace ok. ******************************************************************/ #include #include #include #include /*------ 18 point xform -------*/ float mdct18w[18]; // effectively constant float mdct18w2[9]; // " " float coef[9][4]; // " " float mdct6_3v[6]; // " " float mdct6_3v2[3]; // " " float coef87; // " " typedef struct { float *w; float *w2; void *coef; } IMDCT_INIT_BLOCK; static const IMDCT_INIT_BLOCK imdct_info_18 = {mdct18w, mdct18w2, coef}; static const IMDCT_INIT_BLOCK imdct_info_6 = {mdct6_3v, mdct6_3v2, &coef87}; /*====================================================================*/ const IMDCT_INIT_BLOCK *imdct_init_addr_18() { return &imdct_info_18; } const IMDCT_INIT_BLOCK *imdct_init_addr_6() { return &imdct_info_6; } /*--------------------------------------------------------------------*/ void imdct18(float f[18]) /* 18 point */ { int p; float a[9], b[9]; float ap, bp, a8p, b8p; float g1, g2; for (p = 0; p < 4; p++) { g1 = mdct18w[p] * f[p]; g2 = mdct18w[17 - p] * f[17 - p]; ap = g1 + g2; // a[p] bp = mdct18w2[p] * (g1 - g2); // b[p] g1 = mdct18w[8 - p] * f[8 - p]; g2 = mdct18w[9 + p] * f[9 + p]; a8p = g1 + g2; // a[8-p] b8p = mdct18w2[8 - p] * (g1 - g2); // b[8-p] a[p] = ap + a8p; a[5 + p] = ap - a8p; b[p] = bp + b8p; b[5 + p] = bp - b8p; } g1 = mdct18w[p] * f[p]; g2 = mdct18w[17 - p] * f[17 - p]; a[p] = g1 + g2; b[p] = mdct18w2[p] * (g1 - g2); f[0] = 0.5f * (a[0] + a[1] + a[2] + a[3] + a[4]); f[1] = 0.5f * (b[0] + b[1] + b[2] + b[3] + b[4]); f[2] = coef[1][0] * a[5] + coef[1][1] * a[6] + coef[1][2] * a[7] + coef[1][3] * a[8]; f[3] = coef[1][0] * b[5] + coef[1][1] * b[6] + coef[1][2] * b[7] + coef[1][3] * b[8] - f[1]; f[1] = f[1] - f[0]; f[2] = f[2] - f[1]; f[4] = coef[2][0] * a[0] + coef[2][1] * a[1] + coef[2][2] * a[2] + coef[2][3] * a[3] - a[4]; f[5] = coef[2][0] * b[0] + coef[2][1] * b[1] + coef[2][2] * b[2] + coef[2][3] * b[3] - b[4] - f[3]; f[3] = f[3] - f[2]; f[4] = f[4] - f[3]; f[6] = coef[3][0] * (a[5] - a[7] - a[8]); f[7] = coef[3][0] * (b[5] - b[7] - b[8]) - f[5]; f[5] = f[5] - f[4]; f[6] = f[6] - f[5]; f[8] = coef[4][0] * a[0] + coef[4][1] * a[1] + coef[4][2] * a[2] + coef[4][3] * a[3] + a[4]; f[9] = coef[4][0] * b[0] + coef[4][1] * b[1] + coef[4][2] * b[2] + coef[4][3] * b[3] + b[4] - f[7]; f[7] = f[7] - f[6]; f[8] = f[8] - f[7]; f[10] = coef[5][0] * a[5] + coef[5][1] * a[6] + coef[5][2] * a[7] + coef[5][3] * a[8]; f[11] = coef[5][0] * b[5] + coef[5][1] * b[6] + coef[5][2] * b[7] + coef[5][3] * b[8] - f[9]; f[9] = f[9] - f[8]; f[10] = f[10] - f[9]; f[12] = 0.5f * (a[0] + a[2] + a[3]) - a[1] - a[4]; f[13] = 0.5f * (b[0] + b[2] + b[3]) - b[1] - b[4] - f[11]; f[11] = f[11] - f[10]; f[12] = f[12] - f[11]; f[14] = coef[7][0] * a[5] + coef[7][1] * a[6] + coef[7][2] * a[7] + coef[7][3] * a[8]; f[15] = coef[7][0] * b[5] + coef[7][1] * b[6] + coef[7][2] * b[7] + coef[7][3] * b[8] - f[13]; f[13] = f[13] - f[12]; f[14] = f[14] - f[13]; f[16] = coef[8][0] * a[0] + coef[8][1] * a[1] + coef[8][2] * a[2] + coef[8][3] * a[3] + a[4]; f[17] = coef[8][0] * b[0] + coef[8][1] * b[1] + coef[8][2] * b[2] + coef[8][3] * b[3] + b[4] - f[15]; f[15] = f[15] - f[14]; f[16] = f[16] - f[15]; f[17] = f[17] - f[16]; return; } /*--------------------------------------------------------------------*/ /* does 3, 6 pt dct. changes order from f[i][window] c[window][i] */ void imdct6_3(float f[]) /* 6 point */ { int w; float buf[18]; float *a, *c; // b[i] = a[3+i] float g1, g2; float a02, b02; c = f; a = buf; for (w = 0; w < 3; w++) { g1 = mdct6_3v[0] * f[3 * 0]; g2 = mdct6_3v[5] * f[3 * 5]; a[0] = g1 + g2; a[3 + 0] = mdct6_3v2[0] * (g1 - g2); g1 = mdct6_3v[1] * f[3 * 1]; g2 = mdct6_3v[4] * f[3 * 4]; a[1] = g1 + g2; a[3 + 1] = mdct6_3v2[1] * (g1 - g2); g1 = mdct6_3v[2] * f[3 * 2]; g2 = mdct6_3v[3] * f[3 * 3]; a[2] = g1 + g2; a[3 + 2] = mdct6_3v2[2] * (g1 - g2); a += 6; f++; } a = buf; for (w = 0; w < 3; w++) { a02 = (a[0] + a[2]); b02 = (a[3 + 0] + a[3 + 2]); c[0] = a02 + a[1]; c[1] = b02 + a[3 + 1]; c[2] = coef87 * (a[0] - a[2]); c[3] = coef87 * (a[3 + 0] - a[3 + 2]) - c[1]; c[1] = c[1] - c[0]; c[2] = c[2] - c[1]; c[4] = a02 - a[1] - a[1]; c[5] = b02 - a[3 + 1] - a[3 + 1] - c[3]; c[3] = c[3] - c[2]; c[4] = c[4] - c[3]; c[5] = c[5] - c[4]; a += 6; c += 6; } return; } /*--------------------------------------------------------------------*/