gstreamer/gst-libs/gst/idct/fastintidct.c

/* 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
 * 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.
 *
 */

/**********************************************************/
/* 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       */
/**********************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

/* this code assumes >> to be a two's-complement arithmetic */
/* right shift: (-2)>>1 == -1 , (-3)>>1 == -2               */

#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) */

#include "dct.h"

/* private data */
static short iclip[1024];       /* clipping table */
static short *iclp;

/* private prototypes */
static void idctrow (short *blk);
static void idctcol (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
idctrow (blk)
     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 (blk)
     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
gst_idct_fast_int_idct (block)
     short *block;
{
  int i;

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

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

void
gst_idct_init_fast_int_idct ()
{
  int i;

  iclp = iclip + 512;
  for (i = -512; i < 512; i++)
    iclp[i] = (i < -256) ? -256 : ((i > 255) ? 255 : i);
}