gusucode.com > 一个可以在局域网进行视频聊天的源代码 > 一个可以在局域网进行视频聊天的源代码/VoIP/decoder/Idctref.cpp
//////////////////////////////////////////////////////////////////////////// // // // Project : VideoNet version 1.1. // Description : Peer to Peer Video Conferencing over the LAN. // Author : Nagareshwar Y Talekar ( nsry2002@yahoo.co.in) // Date : 15-6-2004. // // This is the modified version of tmndecode (H.263 decoder) // written by Karl & Robert.It was in ANSI C. I have converted into C++ // so that it can be integrated into any windows application. I have // removed some of the files which had display and file storing // functions.I have removed the unnecessary code and also added some // new files.. // Original library dealt with files. Input & Output , both were files. // I have done some major changes so that it can be used for real time // decoding process. Now one can use this library for decoding H263 frames. // // // File description : // Name : Idctref.cpp // ///////////////////////////////////////////////////////////////////////////// /************************************************************************ * * idctref.c, inverse DCT, double precision, for tmndecode (H.263 decoder) * Copyright (C) 1996 Telenor R&D, Norway * Karl Olav Lillevold <Karl.Lillevold@nta.no> * * 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. * * Karl Olav Lillevold <Karl.Lillevold@nta.no> * Telenor Research and Development * P.O.Box 83 tel.: +47 63 84 84 00 * N-2007 Kjeller, Norway fax.: +47 63 81 00 76 * * Robert Danielsen e-mail: Robert.Danielsen@nta.no * Telenor Research and Development www: http://www.nta.no/brukere/DVC/ * P.O.Box 83 tel.: +47 63 84 84 00 * N-2007 Kjeller, Norway fax.: +47 63 81 00 76 * ************************************************************************/ /* * based on mpeg2decode, (C) 1994, MPEG Software Simulation Group * and mpeg2play, (C) 1994 Stefan Eckart * <stefan@lis.e-technik.tu-muenchen.de> * */ /* 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 */ #include "Idctref.h" #ifndef PI # ifdef M_PI # define PI M_PI # else # define PI 3.14159265358979323846 # endif #endif /* global declarations */ void init_idctref (); void idctref (short *block); /* private data */ /* cosine transform matrix for 8x1 IDCT */ static double c[8][8]; /* initialize DCT coefficient matrix */ void init_idctref() { 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++) c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5)); } } /* perform IDCT matrix multiply for 8x8 coefficient block */ void idctref(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+= 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+= 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); } }