/* idct.c, inverse fast discrete cosine transform                           */

/* 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
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 *
 * This disclaimer of warranty extends to the user of these programs and user's
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 *
 * The MPEG Software Simulation Group does not represent or warrant that the
 * programs furnished hereunder are free of infringement of any third-party
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 * are subject to royalty fees to patent holders.  Many of these patents are
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/**********************************************************/
/* 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_clip_table.h"

#define W1 2841 /* 2048*sqrt(2)*cos(1*pi/16) */
#define W2 2676 /* 2048*sqrt(2)*cos(2*pi/16) */
#define W3 2408 /* 2048*sqrt(2)*cos(3*pi/16) */
#define W5 1609 /* 2048*sqrt(2)*cos(5*pi/16) */
#define W6 1108 /* 2048*sqrt(2)*cos(6*pi/16) */
#define W7 565  /* 2048*sqrt(2)*cos(7*pi/16) */


void __stdcall idct_int32(short *block);

static void idct_row(short *blk);
static void idct_col(short *blk);

/* 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 idct_row(short *blk)
{
	int x0, x1, x2, x3, x4, x5, x6, x7, x8;

	x1 = blk[4]<<11;
	x2 = blk[6];
	x3 = blk[2];
	x4 = blk[1];
	x5 = blk[7];
	x6 = blk[5];
	x7 = blk[3];

	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 idct_col(short *blk)
{
	int x0, x1, x2, x3, x4, x5, x6, x7, x8;

	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];

	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] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x7+x1)>>14)];
	blk[8*1] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x3+x2)>>14)];
	blk[8*2] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x0+x4)>>14)];
	blk[8*3] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x8+x6)>>14)];
	blk[8*4] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x8-x6)>>14)];
	blk[8*5] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x0-x4)>>14)];
	blk[8*6] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x3-x2)>>14)];
	blk[8*7] = idct_clip_table[IDCT_CLIP_TABLE_OFFSET+((x7-x1)>>14)];
}

/* two dimensional inverse discrete cosine transform */
void __stdcall idct_int32(short *block)
{
  int i;

  for (i=0; i<8; i++)
    idct_row(block+8*i);

  for (i=0; i<8; i++)
    idct_col(block+i);
}