📄 cook_mdct.c

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    r1 = x1[7] - x2[7]; x1[7] += x2[7];
    XNPROD31( r0, r1, T[0], T[1], &x2[6], &x2[7] ); T-=step;

    r0 = x1[4] - x2[4]; x1[4] += x2[4];
    r1 = x1[5] - x2[5]; x1[5] += x2[5];
    XNPROD31( r0, r1, T[0], T[1], &x2[4], &x2[5] ); T-=step;

    r0 = x1[2] - x2[2]; x1[2] += x2[2];
    r1 = x1[3] - x2[3]; x1[3] += x2[3];
    XNPROD31( r0, r1, T[0], T[1], &x2[2], &x2[3] ); T-=step;

    r0 = x1[0] - x2[0]; x1[0] += x2[0];
    r1 = x1[1] - x2[1]; x1[1] += x2[1];
    XNPROD31( r0, r1, T[0], T[1], &x2[0], &x2[1] ); T-=step;

    x1-=8; x2-=8;
  }while(T>sincos_lookup);
  do{
    r0 = x2[6] - x1[6]; x1[6] += x2[6];
    r1 = x2[7] - x1[7]; x1[7] += x2[7];
    XPROD31( r0, r1, T[0], T[1], &x2[6], &x2[7] ); T+=step;

    r0 = x2[4] - x1[4]; x1[4] += x2[4];
    r1 = x2[5] - x1[5]; x1[5] += x2[5];
    XPROD31( r0, r1, T[0], T[1], &x2[4], &x2[5] ); T+=step;

    r0 = x2[2] - x1[2]; x1[2] += x2[2];
    r1 = x2[3] - x1[3]; x1[3] += x2[3];
    XPROD31( r0, r1, T[0], T[1], &x2[2], &x2[3] ); T+=step;

    r0 = x2[0] - x1[0]; x1[0] += x2[0];
    r1 = x2[1] - x1[1]; x1[1] += x2[1];
    XPROD31( r0, r1, T[0], T[1], &x2[0], &x2[1] ); T+=step;

    x1-=8; x2-=8;
  }while(T<sincos_lookup+2048);
  do{
    r0 = x1[6] - x2[6]; x1[6] += x2[6];
    r1 = x2[7] - x1[7]; x1[7] += x2[7];
    XNPROD31( r1, r0, T[0], T[1], &x2[6], &x2[7] ); T-=step;

    r0 = x1[4] - x2[4]; x1[4] += x2[4];
    r1 = x2[5] - x1[5]; x1[5] += x2[5];
    XNPROD31( r1, r0, T[0], T[1], &x2[4], &x2[5] ); T-=step;

    r0 = x1[2] - x2[2]; x1[2] += x2[2];
    r1 = x2[3] - x1[3]; x1[3] += x2[3];
    XNPROD31( r1, r0, T[0], T[1], &x2[2], &x2[3] ); T-=step;

    r0 = x1[0] - x2[0]; x1[0] += x2[0];
    r1 = x2[1] - x1[1]; x1[1] += x2[1];
    XNPROD31( r1, r0, T[0], T[1], &x2[0], &x2[1] ); T-=step;

    x1-=8; x2-=8;
  }while(T>sincos_lookup);
}

STIN void mdct_butterflies
(DATA_TYPE *x,int points,int shift,LOOKUP_T *sincos_lookup){

  int stages=8-shift;
  int i,j;
  
  for(i=0;--stages>0;i++){
    for(j=0;j<(1<<i);j++)
      mdct_butterfly_generic(x+(points>>i)*j,points>>i,8<<(i+shift),
                             sincos_lookup);
  }

  for(j=0;j<points;j+=32)
    mdct_butterfly_32(x+j);

}

static unsigned char bitrev[16]={0,8,4,12,2,10,6,14,1,9,5,13,3,11,7,15};

STIN int bitrev12(int x){
  return bitrev[x>>8]|(bitrev[(x&0x0f0)>>4]<<4)|(((int)bitrev[x&0x00f])<<8);
}

STIN void mdct_bitreverse
(DATA_TYPE *x,int n,int step,int shift,LOOKUP_T *sincos_lookup){

  int          bit   = 0;
  DATA_TYPE   *w0    = x;
  DATA_TYPE   *w1    = x = w0+(n>>1);
  LOOKUP_T    *T = sincos_lookup+(step>>1);
  LOOKUP_T    *Ttop  = T+2048;
  DATA_TYPE    r2;

  //av_log(0, 0, "brev: shift=%d, step=%d\n", shift, step);

  do{
    DATA_TYPE r3     = bitrev12(bit++);
    DATA_TYPE *x0    = x + ((r3 ^ 0xfff)>>shift) -1;
    DATA_TYPE *x1    = x + (r3>>shift);

    REG_TYPE  r0     = x0[0]  + x1[0];
    REG_TYPE  r1     = x1[1]  - x0[1];

	      XPROD32( r0, r1, T[1], T[0], &r2, &r3 ); T+=step;

	      w1    -= 4;

	      r0     = (x0[1] + x1[1])>>1;
              r1     = (x0[0] - x1[0])>>1;
	      w0[0]  = r0     + r2;
	      w0[1]  = r1     + r3;
	      w1[2]  = r0     - r2;
	      w1[3]  = r3     - r1;

	      r3     = bitrev12(bit++);
              x0     = x + ((r3 ^ 0xfff)>>shift) -1;
              x1     = x + (r3>>shift);

              r0     = x0[0]  + x1[0];
              r1     = x1[1]  - x0[1];

	      XPROD32( r0, r1, T[1], T[0], &r2, &r3 ); T+=step;

              r0     = (x0[1] + x1[1])>>1;
              r1     = (x0[0] - x1[0])>>1;
	      w0[2]  = r0     + r2;
	      w0[3]  = r1     + r3;
	      w1[0]  = r0     - r2;
	      w1[1]  = r3     - r1;

	      w0    += 4;
  }while(T<Ttop);
  do{
    DATA_TYPE r3     = bitrev12(bit++);
    DATA_TYPE *x0    = x + ((r3 ^ 0xfff)>>shift) -1;
    DATA_TYPE *x1    = x + (r3>>shift);

    REG_TYPE  r0     = x0[0]  + x1[0];
    REG_TYPE  r1     = x1[1]  - x0[1];

	      T-=step; XPROD32( r0, r1, T[0], T[1], &r2, &r3 );

	      w1    -= 4;

	      r0     = (x0[1] + x1[1])>>1;
              r1     = (x0[0] - x1[0])>>1;
	      w0[0]  = r0     + r2;
	      w0[1]  = r1     + r3;
	      w1[2]  = r0     - r2;
	      w1[3]  = r3     - r1;

	      r3     = bitrev12(bit++);
              x0     = x + ((r3 ^ 0xfff)>>shift) -1;
              x1     = x + (r3>>shift);

              r0     = x0[0]  + x1[0];
              r1     = x1[1]  - x0[1];

	      T-=step; XPROD32( r0, r1, T[0], T[1], &r2, &r3 );

              r0     = (x0[1] + x1[1])>>1;
              r1     = (x0[0] - x1[0])>>1;
	      w0[2]  = r0     + r2;
	      w0[3]  = r1     + r3;
	      w1[0]  = r0     - r2;
	      w1[1]  = r3     - r1;

	      w0    += 4;
  }while(w0<w1);
}

STIN void cook_mdct_backward
(int n, DATA_TYPE *in, DATA_TYPE *out, LOOKUP_T *sincos_lookup){

  int n2=n>>1;
  int n4=n>>2;
  DATA_TYPE *iX;
  DATA_TYPE *oX;
  LOOKUP_T *T;
  int shift;
  int step;

  for (shift=6;!(n&(1<<shift));shift++);

  shift=13-shift;
  step=4<<shift;
  //step=16;
  //av_log(0, 0, "mdct: shift=%d, step=%d\n", shift, step);
   
  /* rotate */

  iX            = in+n2-7;
  oX            = out+n2+n4;
  T             = sincos_lookup;

  do{
    oX-=4;
    XPROD31( iX[4], iX[6], T[0], T[1], &oX[2], &oX[3] ); T+=step;
    XPROD31( iX[0], iX[2], T[0], T[1], &oX[0], &oX[1] ); T+=step;
    iX-=8;
  }while(iX>=in+n4);
  do{
    oX-=4;
    XPROD31( iX[4], iX[6], T[1], T[0], &oX[2], &oX[3] ); T-=step;
    XPROD31( iX[0], iX[2], T[1], T[0], &oX[0], &oX[1] ); T-=step;
    iX-=8;
  }while(iX>=in);

  iX            = in+n2-8;
  oX            = out+n2+n4;
  T             = sincos_lookup;

  do{
    T+=step; XNPROD31( iX[6], iX[4], T[0], T[1], &oX[0], &oX[1] );
    T+=step; XNPROD31( iX[2], iX[0], T[0], T[1], &oX[2], &oX[3] );
    iX-=8;
    oX+=4;
  }while(iX>=in+n4);
  do{
    T-=step; XNPROD31( iX[6], iX[4], T[1], T[0], &oX[0], &oX[1] );
    T-=step; XNPROD31( iX[2], iX[0], T[1], T[0], &oX[2], &oX[3] );
    iX-=8;
    oX+=4;
  }while(iX>=in);

  mdct_butterflies(out+n2,n2,shift,sincos_lookup);
  mdct_bitreverse(out,n,step,shift,sincos_lookup);

  /* rotate */

  step>>=2;
  //step=4;
  {
    DATA_TYPE *oX1=out+n2+n4;
    DATA_TYPE *oX2=out+n2+n4;
    DATA_TYPE *iX =out;

    T=sincos_lookup+(step>>1);
    do{
      oX1-=4;
      XPROD31( iX[0], -iX[1], T[0], T[1], &oX1[3], &oX2[0] ); T+=step;
      XPROD31( iX[2], -iX[3], T[0], T[1], &oX1[2], &oX2[1] ); T+=step;
      XPROD31( iX[4], -iX[5], T[0], T[1], &oX1[1], &oX2[2] ); T+=step;
      XPROD31( iX[6], -iX[7], T[0], T[1], &oX1[0], &oX2[3] ); T+=step;
      oX2+=4;
      iX+=8;
    }while(iX<oX1);

    iX=out+n2+n4;
    oX1=out+n4;
    oX2=oX1;

    do{
      oX1-=4;
      iX-=4;

      oX2[0] = -(oX1[3] = iX[3]);
      oX2[1] = -(oX1[2] = iX[2]);
      oX2[2] = -(oX1[1] = iX[1]);
      oX2[3] = -(oX1[0] = iX[0]);

      oX2+=4;
    }while(oX2<iX);

    iX=out+n2+n4;
    oX1=out+n2+n4;
    oX2=out+n2;

    do{
      oX1-=4;
      oX1[0]= iX[3];
      oX1[1]= iX[2];
      oX1[2]= iX[1];
      oX1[3]= iX[0];
      iX+=4;
    }while(oX1>oX2);
  }
}
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