www.pudn.com > h263_.rar > Idct.cpp

// Idct.cpp: implementation of the CIdct class. 
// 
////////////////////////////////////////////////////////////////////// 
 
#include "stdafx.h" 
#include "视频编解码器.h" 
#include "Idct.h" 
#include  
 
 
#ifdef _DEBUG 
#undef THIS_FILE 
static char THIS_FILE[]=__FILE__; 
#define new DEBUG_NEW 
#endif 
 
////////////////////////////////////////////////////////////////////// 
// Construction/Destruction 
////////////////////////////////////////////////////////////////////// 
#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) */ 
 
# ifndef PI 
# ifdef M_PI 
#  define PI M_PI 
# else 
#  define PI 3.14159265358979323846 
# endif 
# endif 
// cosine transform matrix for 8x1 IDCT  
static double c[8][8]; 
static short iclip[1024]; // clipping table  
static short *iclp; 
 
CIdct::CIdct() 
{ 
 
} 
 
CIdct::~CIdct() 
{ 
 
} 
 
void CIdct::idct(short *block) 
{ 
  int i; 
  //行IDCT 
  for (i=0; i<8; i++) 
   idctrow(block+8*i); 
  //列IDCT 
  for (i=0; i<8; i++) 
    idctcol(block+i); 
} 
 
void CIdct::init_idct() 
{ 
  int i; 
  iclp = iclip+512; 
  for (i= -512; i<512; i++)//iclp的取间是[-256 255] 
    iclp[i] = (i<-256) ? -256 : ((i>255) ? 255 : i); 
} 
//根据公式的变换DCT 
//初始化系数 
void CIdct::init_idctref() 
{ 
  int freq, time; 
  double scale; 
 
  for (freq=0; freq < 8; freq++) 
  { 
    scale = (freq == 0) ? sqrt(0.125) : 0.5; 
    for (time=0; time<8; time++) 
      c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5)); 
  } 
 
} 
//直接变换DCT 
void CIdct::idctref(short *block) 
{ 
 int i, j, k, v; 
  double partial_product; 
  double tmp[64]; 
 
  for (i=0; i<8; i++) 
    for (j=0; j<8; j++) 
    { 
      partial_product = 0.0; 
 
      for (k=0; k<8; k++) 
        partial_product+= c[k][j]*block[8*i+k]; 
 
      tmp[8*i+j] = partial_product; 
    } 
 
  // Transpose operation is integrated into address mapping  
  //  by switching loop order of i and j  
 
  for (j=0; j<8; j++) 
    for (i=0; i<8; i++) 
    { 
      partial_product = 0.0; 
      for (k=0; k<8; k++) 
        partial_product+= c[k][i]*tmp[8*k+j]; 
      v =(int) floor(partial_product+0.5); 
      block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v); 
	} 
} 
/* 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) 
 */ 
//  
void CIdct::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) 
 */ 
 
void CIdct::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];//截取 
  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]; 
}