newmdct.c

音频编码

    xr = a[29] - xr;    a[29] = xr;

    xr = a[ 1] - a[ 0]; a[ 1] = xr;
    xr = a[16] - xr;    a[16] = xr;
    xr = a[17] - xr;    a[17] = xr;
    xr = a[ 8] - xr;    a[ 8] = xr;
    xr = a[ 9] - xr;    a[ 9] = xr;
    xr = a[24] - xr;    a[24] = xr;
    xr = a[25] - xr;    a[25] = xr;
    xr = a[ 4] - xr;    a[ 4] = xr;
    xr = a[ 5] - xr;    a[ 5] = xr;
    xr = a[20] - xr;    a[20] = xr;
    xr = a[21] - xr;    a[21] = xr;
    xr = a[12] - xr;    a[12] = xr;
    xr = a[13] - xr;    a[13] = xr;
    xr = a[28] - xr;    a[28] = xr;
    xr = a[29] - xr;    a[29] = xr;

    xr = a[ 0]; a[ 0] += a[31]; a[31] -= xr;
    xr = a[ 1]; a[ 1] += a[30]; a[30] -= xr;
    xr = a[16]; a[16] += a[15]; a[15] -= xr;
    xr = a[17]; a[17] += a[14]; a[14] -= xr;
    xr = a[ 8]; a[ 8] += a[23]; a[23] -= xr;
    xr = a[ 9]; a[ 9] += a[22]; a[22] -= xr;
    xr = a[24]; a[24] += a[ 7]; a[ 7] -= xr;
    xr = a[25]; a[25] += a[ 6]; a[ 6] -= xr;
    xr = a[ 4]; a[ 4] += a[27]; a[27] -= xr;
    xr = a[ 5]; a[ 5] += a[26]; a[26] -= xr;
    xr = a[20]; a[20] += a[11]; a[11] -= xr;
    xr = a[21]; a[21] += a[10]; a[10] -= xr;
    xr = a[12]; a[12] += a[19]; a[19] -= xr;
    xr = a[13]; a[13] += a[18]; a[18] -= xr;
    xr = a[28]; a[28] += a[ 3]; a[ 3] -= xr;
    xr = a[29]; a[29] += a[ 2]; a[ 2] -= xr;
}

}


/*-------------------------------------------------------------------*/
/*                                                                   */
/*   Function: Calculation of the MDCT                               */
/*   In the case of long blocks (type 0,1,3) there are               */
/*   36 coefficents in the time domain and 18 in the frequency       */
/*   domain.                                                         */
/*   In the case of short blocks (type 2) there are 3                */
/*   transformations with short length. This leads to 12 coefficents */
/*   in the time and 6 in the frequency domain. In this case the     */
/*   results are stored side by side in the vector out[].            */
/*                                                                   */
/*   New layer3                                                      */
/*                                                                   */
/*-------------------------------------------------------------------*/

inline static void mdct_short(FLOAT *inout)
{
    int l;
    for ( l = 0; l < 3; l++ ) {
	FLOAT tc0,tc1,tc2,ts0,ts1,ts2;

	ts0 = inout[2*3] * win[SHORT_TYPE][0] - inout[5*3];
	tc0 = inout[0*3] * win[SHORT_TYPE][2] - inout[3*3];
	tc1 = ts0 + tc0;
	tc2 = ts0 - tc0;

	ts0 = inout[5*3] * win[SHORT_TYPE][0] + inout[2*3];
	tc0 = inout[3*3] * win[SHORT_TYPE][2] + inout[0*3];
	ts1 = ts0 + tc0;
	ts2 = -ts0 + tc0;

	tc0 = (inout[1*3] * win[SHORT_TYPE][1] - inout[4*3]) * 2.069978111953089e-11; /* tritab_s[1] */
	ts0 = (inout[4*3] * win[SHORT_TYPE][1] + inout[1*3]) * 2.069978111953089e-11; /* tritab_s[1] */

	inout[3*0] = tc1 * 1.907525191737280e-11 /* tritab_s[2] */ + tc0;
	inout[3*5] = -ts1 * 1.907525191737280e-11 /* tritab_s[0] */ + ts0;

	tc2 = tc2 * 0.86602540378443870761 * 1.907525191737281e-11 /* tritab_s[2] */;
	ts1 = ts1 * 0.5 * 1.907525191737281e-11 + ts0;
	inout[3*1] = tc2-ts1;
	inout[3*2] = tc2+ts1;

	tc1 = tc1 * 0.5 * 1.907525191737281e-11 - tc0;
	ts2 = ts2 * 0.86602540378443870761 * 1.907525191737281e-11 /* tritab_s[0] */;
	inout[3*3] = tc1+ts2;
	inout[3*4] = tc1-ts2;

	inout++;
    }
}

inline static void mdct_long(FLOAT *out, FLOAT *in)
{
    FLOAT ct,st;
  {
    FLOAT tc1, tc2, tc3, tc4, ts5, ts6, ts7, ts8;
    /* 1,2, 5,6, 9,10, 13,14, 17 */
    tc1 = in[17]-in[ 9];
    tc3 = in[15]-in[11];
    tc4 = in[14]-in[12];
    ts5 = in[ 0]+in[ 8];
    ts6 = in[ 1]+in[ 7];
    ts7 = in[ 2]+in[ 6];
    ts8 = in[ 3]+in[ 5];

    out[17] = (ts5+ts7-ts8)-(ts6-in[4]);
    st = (ts5+ts7-ts8)*cx[7]+(ts6-in[4]);
    ct = (tc1-tc3-tc4)*cx[6];
    out[5] = ct+st;
    out[6] = ct-st;

    tc2 = (in[16]-in[10])*cx[6];
    ts6 = ts6*cx[7] + in[4];
    ct =  tc1*cx[0] + tc2 + tc3*cx[1] + tc4*cx[2];
    st = -ts5*cx[4] + ts6 - ts7*cx[5] + ts8*cx[3];
    out[1] = ct+st;
    out[2] = ct-st;

    ct =  tc1*cx[1] - tc2 - tc3*cx[2] + tc4*cx[0];
    st = -ts5*cx[5] + ts6 - ts7*cx[3] + ts8*cx[4];
    out[ 9] = ct+st;
    out[10] = ct-st;

    ct = tc1*cx[2] - tc2 + tc3*cx[0] - tc4*cx[1];
    st = ts5*cx[3] - ts6 + ts7*cx[4] - ts8*cx[5];
    out[13] = ct+st;
    out[14] = ct-st;
  }
  {
    FLOAT ts1, ts2, ts3, ts4, tc5, tc6, tc7, tc8;

    ts1 = in[ 8]-in[ 0];
    ts3 = in[ 6]-in[ 2];
    ts4 = in[ 5]-in[ 3];
    tc5 = in[17]+in[ 9];
    tc6 = in[16]+in[10];
    tc7 = in[15]+in[11];
    tc8 = in[14]+in[12];

    out[0]  = (tc5+tc7+tc8)+(tc6+in[13]);
    ct = (tc5+tc7+tc8)*cx[7]-(tc6+in[13]);
    st = (ts1-ts3+ts4)*cx[6];
    out[11] = ct+st;
    out[12] = ct-st;

    ts2 = (in[7]-in[1])*cx[6];
    tc6 = in[13] - tc6*cx[7];
    ct = tc5*cx[3] - tc6 + tc7*cx[4] + tc8*cx[5];
    st = ts1*cx[2] + ts2 + ts3*cx[0] + ts4*cx[1];
    out[3] = ct+st;
    out[4] = ct-st;

    ct = -tc5*cx[5] + tc6 - tc7*cx[3] - tc8*cx[4];
    st =  ts1*cx[1] + ts2 - ts3*cx[2] - ts4*cx[0];
    out[7] = ct+st;
    out[8] = ct-st;

    ct = -tc5*cx[4] + tc6 - tc7*cx[5] - tc8*cx[3];
    st =  ts1*cx[0] - ts2 + ts3*cx[1] - ts4*cx[2];
    out[15] = ct+st;
    out[16] = ct-st;
  }
}


void mdct_sub48(
    lame_internal_flags *gfc, const sample_t *w0, const sample_t *w1
    )
{
    int gr, k, ch;
    const sample_t *wk;

    wk = w0 + 286;
    /* thinking cache performance, ch->gr loop is better than gr->ch loop */
    for (ch = 0; ch < gfc->channels_out; ch++) {
	for (gr = 0; gr < gfc->mode_gr; gr++) {
	    int	band;
	    gr_info *gi = &(gfc->l3_side.tt[gr][ch]);
	    FLOAT *mdct_enc = gi->xr;
	    FLOAT *samp = gfc->sb_sample[ch][1 - gr][0];

	    for (k = 0; k < 18 / 2; k++) {
		window_subband(wk, samp);
		window_subband(wk + 32, samp + 32);
		samp += 64;
		wk += 64;
		/*
		 * Compensate for inversion in the analysis filter
		 */
		for (band = 1; band < 32; band+=2) {
		    samp[band-32] *= -1;
		}
	    }

	    /*
	     * Perform imdct of 18 previous subband samples
	     * + 18 current subband samples
	     */
	    for (band = 0; band < 32; band++, mdct_enc += 18) {
		int type = gi->block_type;
		FLOAT *band0, *band1;
		band0 = gfc->sb_sample[ch][  gr][0] + order[band];
		band1 = gfc->sb_sample[ch][1-gr][0] + order[band];
		if (gi->mixed_block_flag && band < 2)
		    type = 0;
		if (gfc->amp_filter[band] == 0.0) {
		    memset(mdct_enc, 0, 18*sizeof(FLOAT));
		} else {
		  if (gfc->amp_filter[band] != 1.0) {
		      for (k=0; k<18; k++)
			  band1[k*32] *= gfc->amp_filter[band];
		  }
		  if (type == SHORT_TYPE) {
		    for (k = -NS/4; k < 0; k++) {
			FLOAT w = win[SHORT_TYPE][k+3];
			mdct_enc[k*3+ 9] = band0[( 9+k)*32] * w - band0[( 8-k)*32];
			mdct_enc[k*3+18] = band0[(14-k)*32] * w + band0[(15+k)*32];
			mdct_enc[k*3+10] = band0[(15+k)*32] * w - band0[(14-k)*32];
			mdct_enc[k*3+19] = band1[( 2-k)*32] * w + band1[( 3+k)*32];
			mdct_enc[k*3+11] = band1[( 3+k)*32] * w - band1[( 2-k)*32];
			mdct_enc[k*3+20] = band1[( 8-k)*32] * w + band1[( 9+k)*32];
		    }
		    mdct_short(mdct_enc);
		  } else {
		    FLOAT work[18];
		    for (k = -NL/4; k < 0; k++) {
			FLOAT a, b;
			a = win[type][k+27] * band1[(k+9)*32]
			  + win[type][k+36] * band1[(8-k)*32];
			b = win[type][k+ 9] * band0[(k+9)*32]
			  - win[type][k+18] * band0[(8-k)*32];
			work[k+ 9] = a - b*tantab_l[k+9];
			work[k+18] = a*tantab_l[k+9] + b;
		    }

		    mdct_long(mdct_enc, work);
		  }
		}
		/*
		 * Perform aliasing reduction butterfly
		 */
		if (type != SHORT_TYPE && band != 0) {
		  for (k = 7; k >= 0; --k) {
		    FLOAT bu,bd;
		    bu = mdct_enc[k] * ca[k] + mdct_enc[-1-k] * cs[k];
		    bd = mdct_enc[k] * cs[k] - mdct_enc[-1-k] * ca[k];
		    
		    mdct_enc[-1-k] = bu;
		    mdct_enc[k]    = bd;
		  }
		}
	      }
	}
	wk = w1 + 286;
	if (gfc->mode_gr == 1) {
	    memcpy(gfc->sb_sample[ch][0], gfc->sb_sample[ch][1], 576 * sizeof(FLOAT));
	}
    }
}