text: /*****************************************************************************
   *
   *  XVID MPEG-4 VIDEO CODEC
   *  - Inverse DCT  -
   *
   *  These routines are from Independent JPEG Group's free JPEG software
   *  Copyright (C) 1991-1998, Thomas G. Lane (see the file README.IJG)
   *
   *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
   *
   * $Id: idct.cpp,v 1.2 2006-12-13 15:12:27 jeanlf Exp $
   *
   ****************************************************************************/
  
  /* 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.
   *
   * MPEG2AVI
   * --------
   * v0.16B33 renamed the initialization function to init_idct_int32()
   * v0.16B32 removed the unused idct_row() and idct_col() functions
   * v0.16B3  changed var declarations to static, to enforce data align
   * v0.16B22  idct_FAST() renamed to idct_int32()
   *        also merged idct_FAST() into a single function, to help VC++
   *        optimize it.
   *
   * v0.14  changed int to long, to avoid confusion when compiling on x86
   *        platform ( in VC++ "int" -> 32bits )
   */
  
  /**********************************************************/
  /* 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 "Decoder.h"
  
  const int __W1 = 2841,        //2048*sqrt(2)*cos(1*pi/16)
            __W2 = 2676,               // 2048*sqrt(2)*cos(2*pi/16)
            __W3 = 2408,               // 2048*sqrt(2)*cos(3*pi/16)
            __W5 = 1609,               // 2048*sqrt(2)*cos(5*pi/16)
            __W6 = 1108,               // 2048*sqrt(2)*cos(6*pi/16)
            __W7 = 565;                // 2048*sqrt(2)*cos(7*pi/16)
  
  //----------------------------
  /* two dimensional inverse discrete cosine transform */
  //idct_int32_init() must be called before the first call to this function!
  void S_decoder::InverseDiscreteCosineTransform(int *block) const {
  
  	const t_clip_val *iclp = iclip + 512;
  #if defined USE_ARM_ASM
  	void InverseDiscreteCosineTransform_ARM(int *block, const int *iclip);
  	InverseDiscreteCosineTransform_ARM(block, iclp);
  #else
  	int i;
  	//idct rows
  	for(i = 8; i--; block += 8) {
  		int X0 = block[0];
  		int X1, X2, X3, X4, X5, X6, X7;
  		if(!((X1 = block[4]) | (X2 = block[6]) | (X3 = block[2]) | (X4 = block[1]) | (X5 = block[7]) | (X6 = block[5]) | (X7 = block[3]))) {
  			block[0] = block[1] = block[2] = block[3] = block[4] = block[5] = block[6] = block[7] = X0 << 3;
  			continue;
  		}
  		//for proper rounding in the fourth stage
  		X0 = (X0 << 11) + 128;
  		X1 <<= 11;
  
  		//first stage
  		int 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
  		block[0] = ((X7 + X1) >> 8);
  		block[1] = ((X3 + X2) >> 8);
  		block[2] = ((X0 + X4) >> 8);
  		block[3] = ((X8 + X6) >> 8);
  		block[4] = ((X8 - X6) >> 8);
  		block[5] = ((X0 - X4) >> 8);
  		block[6] = ((X3 - X2) >> 8);
  		block[7] = ((X7 - X1) >> 8);
  	}
  	block -= 8*8;
  	//idct columns
  	for(i = 8; i--; ++block) {
  		int X0 = block[8 * 0];
  		int X1, X2, X3, X4, X5, X6, X7;
  		//shortcut
  		if(!((X1 = block[8 * 4]) | (X2 = block[8 * 6]) | (X3 = block[8 * 2]) | (X4 = block[8 * 1]) | (X5 = block[8 * 7]) | (X6 = block[8 * 5]) | (X7 = block[8 * 3]))) {
  			block[8 * 0] = block[8 * 1] = block[8 * 2] = block[8 * 3] = block[8 * 4] = block[8 * 5] = block[8 * 6] = block[8 * 7] = iclp[(X0 + 32) >> 6];
  			continue;
  		}
  		X0 = (X0 << 8) + 8192;
  		X1 <<= 8;
  
  		//first stage
  		int 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
  		block[8 * 0] = iclp[(X7 + X1) >> 14];
  		block[8 * 1] = iclp[(X3 + X2) >> 14];
  		block[8 * 2] = iclp[(X0 + X4) >> 14];
  		block[8 * 3] = iclp[(X8 + X6) >> 14];
  		block[8 * 4] = iclp[(X8 - X6) >> 14];
  		block[8 * 5] = iclp[(X0 - X4) >> 14];
  		block[8 * 6] = iclp[(X3 - X2) >> 14];
  		block[8 * 7] = iclp[(X7 - X1) >> 14];
  	}
  #endif
  }
  
  //----------------------------
  
  void S_decoder::idct_int32_init() {
  
  	t_clip_val *iclp = iclip + 512;
  	for(int i = -512; i < 512; i++)
  		iclp[i] = (i < -256) ? -256 : ((i > 255) ? 255 : i);
  }
  
  //----------------------------
  