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/Idct.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 : Idct.cpp // ///////////////////////////////////////////////////////////////////////////// /************************************************************************ * * idct.c, inverse fast DCT 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> * */ /**********************************************************/ /* inverse two dimensional DCT, Chen-Wang algorithm */ /* (cf. IEEE ASSP-32, pp. 803-816, Aug. 1984) */ /* 32-bit integer arithmetic (8 bit coefficients) */ /* 11 mults, 29 adds per DCT */ /* sE, 18.8.91 */ /**********************************************************/ /* coefficients extended to 12 bit for IEEE1180-1990 */ /* compliance sE, 2.1.94 */ /**********************************************************/ /* this code assumes >> to be a two's-complement arithmetic */ /* right shift: (-2)>>1 == -1 , (-3)>>1 == -2 */ #include "Idct.h" /* row (horizontal) IDCT * * 7 pi 1 * dst[k] = sum c[l] * src[l] * cos( -- * ( k + - ) * l ) * l=0 8 2 * * where: c[0] = 128 * c[1..7] = 128*sqrt(2) */ static void idctrow(short *blk) { int x0, x1, x2, x3, x4, x5, x6, x7, x8; /* shortcut */ if (!((x1 = blk[4]<<11) | (x2 = blk[6]) | (x3 = blk[2]) | (x4 = blk[1]) | (x5 = blk[7]) | (x6 = blk[5]) | (x7 = blk[3]))) { blk[0]=blk[1]=blk[2]=blk[3]=blk[4]=blk[5]=blk[6]=blk[7]=blk[0]<<3; return; } x0 = (blk[0]<<11) + 128; /* for proper rounding in the fourth stage */ /* first stage */ x8 = W7*(x4+x5); x4 = x8 + (W1-W7)*x4; x5 = x8 - (W1+W7)*x5; x8 = W3*(x6+x7); x6 = x8 - (W3-W5)*x6; x7 = x8 - (W3+W5)*x7; /* second stage */ x8 = x0 + x1; x0 -= x1; x1 = W6*(x3+x2); x2 = x1 - (W2+W6)*x2; x3 = x1 + (W2-W6)*x3; x1 = x4 + x6; x4 -= x6; x6 = x5 + x7; x5 -= x7; /* third stage */ x7 = x8 + x3; x8 -= x3; x3 = x0 + x2; x0 -= x2; x2 = (181*(x4+x5)+128)>>8; x4 = (181*(x4-x5)+128)>>8; /* fourth stage */ blk[0] = (x7+x1)>>8; blk[1] = (x3+x2)>>8; blk[2] = (x0+x4)>>8; blk[3] = (x8+x6)>>8; blk[4] = (x8-x6)>>8; blk[5] = (x0-x4)>>8; blk[6] = (x3-x2)>>8; blk[7] = (x7-x1)>>8; } /* column (vertical) IDCT * * 7 pi 1 * dst[8*k] = sum c[l] * src[8*l] * cos( -- * ( k + - ) * l ) * l=0 8 2 * * where: c[0] = 1/1024 * c[1..7] = (1/1024)*sqrt(2) */ static void idctcol(short *blk) { int x0, x1, x2, x3, x4, x5, x6, x7, x8; /* shortcut */ if (!((x1 = (blk[8*4]<<8)) | (x2 = blk[8*6]) | (x3 = blk[8*2]) | (x4 = blk[8*1]) | (x5 = blk[8*7]) | (x6 = blk[8*5]) | (x7 = blk[8*3]))) { blk[8*0]=blk[8*1]=blk[8*2]=blk[8*3]=blk[8*4]=blk[8*5]=blk[8*6]=blk[8*7]= iclp[(blk[8*0]+32)>>6]; return; } x0 = (blk[8*0]<<8) + 8192; /* first stage */ x8 = W7*(x4+x5) + 4; x4 = (x8+(W1-W7)*x4)>>3; x5 = (x8-(W1+W7)*x5)>>3; x8 = W3*(x6+x7) + 4; x6 = (x8-(W3-W5)*x6)>>3; x7 = (x8-(W3+W5)*x7)>>3; /* second stage */ x8 = x0 + x1; x0 -= x1; x1 = W6*(x3+x2) + 4; x2 = (x1-(W2+W6)*x2)>>3; x3 = (x1+(W2-W6)*x3)>>3; x1 = x4 + x6; x4 -= x6; x6 = x5 + x7; x5 -= x7; /* third stage */ x7 = x8 + x3; x8 -= x3; x3 = x0 + x2; x0 -= x2; x2 = (181*(x4+x5)+128)>>8; x4 = (181*(x4-x5)+128)>>8; /* fourth stage */ blk[8*0] = iclp[(x7+x1)>>14]; blk[8*1] = iclp[(x3+x2)>>14]; blk[8*2] = iclp[(x0+x4)>>14]; blk[8*3] = iclp[(x8+x6)>>14]; blk[8*4] = iclp[(x8-x6)>>14]; blk[8*5] = iclp[(x0-x4)>>14]; blk[8*6] = iclp[(x3-x2)>>14]; blk[8*7] = iclp[(x7-x1)>>14]; } /* two dimensional inverse discrete cosine transform */ void idct(short *block) { int i; for (i=0; i<8; i++) idctrow(block+8*i); for (i=0; i<8; i++) idctcol(block+i); } void init_idct() { int i; iclp = iclip+512; for (i= -512; i<512; i++) iclp[i] = (i<-256) ? -256 : ((i>255) ? 255 : i); }