/* Reference_IDCT.c, Inverse Discrete Fourier Transform, double precision */ /* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */ /* * Disclaimer of Warranty * * These software programs are available to the user without any license fee or * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims * any and all warranties, whether express, implied, or statuary, including any * implied warranties or merchantability or of fitness for a particular * purpose. In no event shall the copyright-holder be liable for any * incidental, punitive, or consequential damages of any kind whatsoever * arising from the use of these programs. * * This disclaimer of warranty extends to the user of these programs and user's * customers, employees, agents, transferees, successors, and assigns. * * The MPEG Software Simulation Group does not represent or warrant that the * programs furnished hereunder are free of infringement of any third-party * patents. * * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, * are subject to royalty fees to patent holders. Many of these patents are * general enough such that they are unavoidable regardless of implementation * design. * */ /* Perform IEEE 1180 reference (64-bit floating point, separable 8x1 * direct matrix multiply) Inverse Discrete Cosine Transform */ /* Here we use math.h to generate constants. Compiler results may vary a little */ #ifdef HAVE_CONFIG_H #include "config.h" #endif #include <math.h> #ifndef PI # ifdef M_PI # define PI M_PI # else # define PI 3.14159265358979323846 # endif #endif /* private data */ /* cosine transform matrix for 8x1 IDCT */ static double gst_idct_float_c[8][8]; /* initialize DCT coefficient matrix */ void gst_idct_init_float_idct () { int freq, time; double scale; for (freq = 0; freq < 8; freq++) { scale = (freq == 0) ? sqrt (0.125) : 0.5; for (time = 0; time < 8; time++) gst_idct_float_c[freq][time] = scale * cos ((PI / 8.0) * freq * (time + 0.5)); } } /* perform IDCT matrix multiply for 8x8 coefficient block */ void gst_idct_float_idct (block) short *block; { int i, j, k, v; double partial_product; double tmp[64]; for (i = 0; i < 8; i++) for (j = 0; j < 8; j++) { partial_product = 0.0; for (k = 0; k < 8; k++) partial_product += gst_idct_float_c[k][j] * block[8 * i + k]; tmp[8 * i + j] = partial_product; } /* Transpose operation is integrated into address mapping by switching loop order of i and j */ for (j = 0; j < 8; j++) for (i = 0; i < 8; i++) { partial_product = 0.0; for (k = 0; k < 8; k++) partial_product += gst_idct_float_c[k][i] * tmp[8 * k + j]; v = (int) floor (partial_product + 0.5); block[8 * i + j] = (v < -256) ? -256 : ((v > 255) ? 255 : v); } }