idct.c

网络MPEG4IP流媒体开发源代码

/* 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.
 *
 * 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 <windows.h>
#include "idct.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) */


/* global declarations */
//void init_idct_int32 (void);
//void idct_int32 (short *block);

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

/* private prototypes */
//static void idctrow _ANSI_ARGS_((short *blk));
//static void idctcol _ANSI_ARGS_((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];
}*/

// function pointer
idctFuncPtr idct;

/* two dimensional inverse discrete cosine transform */
//void j_rev_dct(block)
//short *block;
void idct_int32(short * const block)
{

  // idct_int32_init() must be called before the first call to this function!


  /*int i;
  long i;

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

  for (i=0; i<8; i++)
    idctcol(block+i);*/
  static short *blk;
  static long i;
  static long X0, X1, X2, X3, X4, X5, X6, X7, X8;


  for (i=0; i<8; i++)	// idct rows
  {
	blk = block+(i<<3);
	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;
		continue;
	}

	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] = (short)((X7+X1)>>8);
	blk[1] = (short)((X3+X2)>>8);
	blk[2] = (short)((X0+X4)>>8);
	blk[3] = (short)((X8+X6)>>8);
	blk[4] = (short)((X8-X6)>>8);
	blk[5] = (short)((X0-X4)>>8);
	blk[6] = (short)((X3-X2)>>8);
	blk[7] = (short)((X7-X1)>>8);

  } // end for ( i = 0; i < 8; ++i ) IDCT-rows



  for (i=0; i<8; i++)	// idct columns
  {
	blk = block + i;
    // 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];
		continue;
	}

	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]; 
  }
 
} // end function idct_int32(block)


//void
//idct_int32_init()
void idct_int32_init()
{
  int i;

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