Idct.cpp
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- ////////////////////////////////////////////////////////////////////////////
- //
- //
- // 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);
- }