📄 inv_mdct.cpp
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/* inv_mdct.cpp
*
* Inverse Discrete Cosine Transform for hybrid
* synthesis in MPEG Audio Layer III. Based on the public_c source,
* but almost completely redone by Jeff Tsay and Francois-Raymond Boyer.
*
* Tomilla's 9 point IDCT algorithm has been replaced with Boyer's, which
* is faster. The final output multiplications required by Lee's FDCT
* have been folded into the multiplication by the window.
*
* Last modified : 08/02/97
*/
#include "all.h"
#include "inv_mdct.h"
/*
* This uses Byeong Gi Lee's Fast Cosine Transform algorithm to
* decompose the 36 point and 12 point IDCT's into 9 point and 3
* point IDCT's, respectively. Then the 9 point IDCT is computed
* by Francois-Raymond Boyer's algorithm. See his comments before
* the first 9 point IDCT. The 3 point IDCT is already efficient
* to implement. -- Jeff Tsay.
*/
#ifdef COOLPRO
#pragma optimize("",off) // If full optimizations are done,
#pragma optimize("t",on) // VC 5.0 generates bad code
#endif
real win[4][36] =
{
{ -1.6141214951E-02f, -5.3603178919E-02f, -1.0070713296E-01f, -1.6280817573E-01f,
-4.9999999679E-01f, -3.8388735032E-01f, -6.2061144372E-01f, -1.1659756083E+00f,
-3.8720752656E+00f, -4.2256286556E+00f, -1.5195289984E+00f, -9.7416483388E-01f,
-7.3744074053E-01f, -1.2071067773E+00f, -5.1636156596E-01f, -4.5426052317E-01f,
-4.0715656898E-01f, -3.6969460527E-01f, -3.3876269197E-01f, -3.1242222492E-01f,
-2.8939587111E-01f, -2.6880081906E-01f, -5.0000000266E-01f, -2.3251417468E-01f,
-2.1596714708E-01f, -2.0004979098E-01f, -1.8449493497E-01f, -1.6905846094E-01f,
-1.5350360518E-01f, -1.3758624925E-01f, -1.2103922149E-01f, -2.0710679058E-01f,
-8.4752577594E-02f, -6.4157525656E-02f, -4.1131172614E-02f, -1.4790705759E-02f },
{ -1.6141214951E-02f, -5.3603178919E-02f, -1.0070713296E-01f, -1.6280817573E-01f,
-4.9999999679E-01f, -3.8388735032E-01f, -6.2061144372E-01f, -1.1659756083E+00f,
-3.8720752656E+00f, -4.2256286556E+00f, -1.5195289984E+00f, -9.7416483388E-01f,
-7.3744074053E-01f, -1.2071067773E+00f, -5.1636156596E-01f, -4.5426052317E-01f,
-4.0715656898E-01f, -3.6969460527E-01f, -3.3908542600E-01f, -3.1511810350E-01f,
-2.9642226150E-01f, -2.8184548650E-01f, -5.4119610000E-01f, -2.6213228100E-01f,
-2.5387916537E-01f, -2.3296291359E-01f, -1.9852728987E-01f, -1.5233534808E-01f,
-9.6496400054E-02f, -3.3423828516E-02f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f },
{ -4.8300800645E-02f, -1.5715656932E-01f, -2.8325045177E-01f, -4.2953747763E-01f,
-1.2071067795E+00f, -8.2426483178E-01f, -1.1451749106E+00f, -1.7695290101E+00f,
-4.5470225061E+00f, -3.4890531002E+00f, -7.3296292804E-01f, -1.5076514758E-01f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f },
{ 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f, 0.0000000000E+00f,
0.0000000000E+00f, 0.0000000000E+00f, -1.5076513660E-01f, -7.3296291107E-01f,
-3.4890530566E+00f, -4.5470224727E+00f, -1.7695290031E+00f, -1.1451749092E+00f,
-8.3137738100E-01f, -1.3065629650E+00f, -5.4142014250E-01f, -4.6528974900E-01f,
-4.1066990750E-01f, -3.7004680800E-01f, -3.3876269197E-01f, -3.1242222492E-01f,
-2.8939587111E-01f, -2.6880081906E-01f, -5.0000000266E-01f, -2.3251417468E-01f,
-2.1596714708E-01f, -2.0004979098E-01f, -1.8449493497E-01f, -1.6905846094E-01f,
-1.5350360518E-01f, -1.3758624925E-01f, -1.2103922149E-01f, -2.0710679058E-01f,
-8.4752577594E-02f, -6.4157525656E-02f, -4.1131172614E-02f, -1.4790705759E-02f }
};
void inv_mdct(real *in, real *out, int32 block_type)
{
real tmp[18];
real *win_bt;
int32 i;
if(block_type == 2){
for(int32 p=0;p<36;p+=9) {
out[p] = out[p+1] = out[p+2] = out[p+3] =
out[p+4] = out[p+5] = out[p+6] = out[p+7] =
out[p+8] = 0.0f;
}
int32 six_i = 0;
for(i=0;i<3;i++)
{
// 12 point IMDCT
// Begin 12 point IDCT
// Input aliasing for 12 pt IDCT
in[15+i] += in[12+i]; in[12+i] += in[9+i]; in[9+i] += in[6+i];
in[6+i] += in[3+i]; in[3+i] += in[0+i];
// Input aliasing on odd indices (for 6 point IDCT)
in[15+i] += in[9+i]; in[9+i] += in[3+i];
// 3 point IDCT on even indices
{
real pp1, pp2, sum;
pp2 = in[12+i] * 0.500000000f;
pp1 = in[ 6+i] * 0.866025403f;
sum = in[0+i] + pp2;
tmp[1] = in[0+i] - in[12+i];
tmp[0] = sum + pp1;
tmp[2] = sum - pp1;
// End 3 point IDCT on even indices
// 3 point IDCT on odd indices (for 6 point IDCT)
pp2 = in[15+i] * 0.500000000f;
pp1 = in[ 9+i] * 0.866025403f;
sum = in[ 3+i] + pp2;
tmp[4] = in[3+i] - in[15+i];
tmp[5] = sum + pp1;
tmp[3] = sum - pp1;
}
// End 3 point IDCT on odd indices
// Twiddle factors on odd indices (for 6 point IDCT)
tmp[3] *= 1.931851653f;
tmp[4] *= 0.707106781f;
tmp[5] *= 0.517638090f;
// Output butterflies on 2 3 point IDCT's (for 6 point IDCT)
{
real save = tmp[0];
tmp[0] += tmp[5];
tmp[5] = save - tmp[5];
save = tmp[1];
tmp[1] += tmp[4];
tmp[4] = save - tmp[4];
save = tmp[2];
tmp[2] += tmp[3];
tmp[3] = save - tmp[3];
}
// End 6 point IDCT
// Twiddle factors on indices (for 12 point IDCT)
tmp[0] *= 0.504314480f;
tmp[1] *= 0.541196100f;
tmp[2] *= 0.630236207f;
tmp[3] *= 0.821339815f;
tmp[4] *= 1.306562965f;
tmp[5] *= 3.830648788f;
// End 12 point IDCT
// Shift to 12 point modified IDCT, multiply by window type 2
tmp[8] = -tmp[0] * 0.793353340f;
tmp[9] = -tmp[0] * 0.608761429f;
tmp[7] = -tmp[1] * 0.923879532f;
tmp[10] = -tmp[1] * 0.382683432f;
tmp[6] = -tmp[2] * 0.991444861f;
tmp[11] = -tmp[2] * 0.130526192f;
tmp[0] = tmp[3];
tmp[1] = tmp[4] * 0.382683432f;
tmp[2] = tmp[5] * 0.608761429f;
tmp[3] = -tmp[5] * 0.793353340f;
tmp[4] = -tmp[4] * 0.923879532f;
tmp[5] = -tmp[0] * 0.991444861f;
tmp[0] *= 0.130526192f;
out[six_i + 6] += tmp[0];
out[six_i + 7] += tmp[1];
out[six_i + 8] += tmp[2];
out[six_i + 9] += tmp[3];
out[six_i + 10] += tmp[4];
out[six_i + 11] += tmp[5];
out[six_i + 12] += tmp[6];
out[six_i + 13] += tmp[7];
out[six_i + 14] += tmp[8];
out[six_i + 15] += tmp[9];
out[six_i + 16] += tmp[10];
out[six_i + 17] += tmp[11];
six_i += 6;
}
} else {
// 36 point IDCT
// input aliasing for 36 point IDCT
in[17]+=in[16]; in[16]+=in[15]; in[15]+=in[14]; in[14]+=in[13];
in[13]+=in[12]; in[12]+=in[11]; in[11]+=in[10]; in[10]+=in[9];
in[9] +=in[8]; in[8] +=in[7]; in[7] +=in[6]; in[6] +=in[5];
in[5] +=in[4]; in[4] +=in[3]; in[3] +=in[2]; in[2] +=in[1];
in[1] +=in[0];
// 18 point IDCT for odd indices
// input aliasing for 18 point IDCT
in[17]+=in[15]; in[15]+=in[13]; in[13]+=in[11]; in[11]+=in[9];
in[9] +=in[7]; in[7] +=in[5]; in[5] +=in[3]; in[3] +=in[1];
{
real tmp0,tmp1,tmp2,tmp3,tmp4,tmp0_,tmp1_,tmp2_,tmp3_;
real tmp0o,tmp1o,tmp2o,tmp3o,tmp4o,tmp0_o,tmp1_o,tmp2_o,tmp3_o;
// Fast 9 Point Inverse Discrete Cosine Transform
//
// By Francois-Raymond Boyer
// mailto:boyerf@iro.umontreal.ca
// http://www.iro.umontreal.ca/~boyerf
//
// The code has been optimized for Intel processors
// (takes a lot of time to convert float to and from iternal FPU representation)
//
// It is a simple "factorization" of the IDCT matrix.
// 9 point IDCT on even indices
{
// 5 points on odd indices (not realy an IDCT)
real i0 = in[0]+in[0];
real i0p12 = i0 + in[12];
tmp0 = i0p12 + in[4]*1.8793852415718f + in[8]*1.532088886238f + in[16]*0.34729635533386f;
tmp1 = i0 + in[4] - in[8] - in[12] - in[12] - in[16];
tmp2 = i0p12 - in[4]*0.34729635533386f - in[8]*1.8793852415718f + in[16]*1.532088886238f;
tmp3 = i0p12 - in[4]*1.532088886238f + in[8]*0.34729635533386f - in[16]*1.8793852415718f;
tmp4 = in[0] - in[4] + in[8] - in[12] + in[16];
// 4 points on even indices
real i6_ = in[6]*1.732050808f; // Sqrt[3]
tmp0_ = in[2]*1.9696155060244f + i6_ + in[10]*1.2855752193731f + in[14]*0.68404028665134f;
tmp1_ = (in[2] - in[10] - in[14])*1.732050808f;
tmp2_ = in[2]*1.2855752193731f - i6_ - in[10]*0.68404028665134f + in[14]*1.9696155060244f;
tmp3_ = in[2]*0.68404028665134f - i6_ + in[10]*1.9696155060244f - in[14]*1.2855752193731f;
}
// 9 point IDCT on odd indices
{
// 5 points on odd indices (not realy an IDCT)
real i0 = in[0+1]+in[0+1];
real i0p12 = i0 + in[12+1];
tmp0o = i0p12 + in[4+1]*1.8793852415718f + in[8+1]*1.532088886238f + in[16+1]*0.34729635533386f;
tmp1o = i0 + in[4+1] - in[8+1] - in[12+1] - in[12+1] - in[16+1];
tmp2o = i0p12 - in[4+1]*0.34729635533386f - in[8+1]*1.8793852415718f + in[16+1]*1.532088886238f;
tmp3o = i0p12 - in[4+1]*1.532088886238f + in[8+1]*0.34729635533386f - in[16+1]*1.8793852415718f;
tmp4o = (in[0+1] - in[4+1] + in[8+1] - in[12+1] + in[16+1])*0.707106781f; // Twiddled
// 4 points on even indices
real i6_ = in[6+1]*1.732050808f; // Sqrt[3]
tmp0_o = in[2+1]*1.9696155060244f + i6_ + in[10+1]*1.2855752193731f + in[14+1]*0.68404028665134f;
tmp1_o = (in[2+1] - in[10+1] - in[14+1])*1.732050808f;
tmp2_o = in[2+1]*1.2855752193731f - i6_ - in[10+1]*0.68404028665134f + in[14+1]*1.9696155060244f;
tmp3_o = in[2+1]*0.68404028665134f - i6_ + in[10+1]*1.9696155060244f - in[14+1]*1.2855752193731f;
}
// Twiddle factors on odd indices
// and
// Butterflies on 9 point IDCT's
// and
// twiddle factors for 36 point IDCT
real e, o;
e = tmp0 + tmp0_; o = (tmp0o + tmp0_o)*0.501909918f; tmp[0] = e + o; tmp[17] = e - o;
e = tmp1 + tmp1_; o = (tmp1o + tmp1_o)*0.517638090f; tmp[1] = e + o; tmp[16] = e - o;
e = tmp2 + tmp2_; o = (tmp2o + tmp2_o)*0.551688959f; tmp[2] = e + o; tmp[15] = e - o;
e = tmp3 + tmp3_; o = (tmp3o + tmp3_o)*0.610387294f; tmp[3] = e + o; tmp[14] = e - o;
tmp[4] = tmp4 + tmp4o; tmp[13] = tmp4 - tmp4o;
e = tmp3 - tmp3_; o = (tmp3o - tmp3_o)*0.871723397f; tmp[5] = e + o; tmp[12] = e - o;
e = tmp2 - tmp2_; o = (tmp2o - tmp2_o)*1.183100792f; tmp[6] = e + o; tmp[11] = e - o;
e = tmp1 - tmp1_; o = (tmp1o - tmp1_o)*1.931851653f; tmp[7] = e + o; tmp[10] = e - o;
e = tmp0 - tmp0_; o = (tmp0o - tmp0_o)*5.736856623f; tmp[8] = e + o; tmp[9] = e - o;
}
// end 36 point IDCT */
// shift to modified IDCT
win_bt = win[block_type];
out[0] =-tmp[9] * win_bt[0];
out[1] =-tmp[10] * win_bt[1];
out[2] =-tmp[11] * win_bt[2];
out[3] =-tmp[12] * win_bt[3];
out[4] =-tmp[13] * win_bt[4];
out[5] =-tmp[14] * win_bt[5];
out[6] =-tmp[15] * win_bt[6];
out[7] =-tmp[16] * win_bt[7];
out[8] =-tmp[17] * win_bt[8];
out[9] = tmp[17] * win_bt[9];
out[10]= tmp[16] * win_bt[10];
out[11]= tmp[15] * win_bt[11];
out[12]= tmp[14] * win_bt[12];
out[13]= tmp[13] * win_bt[13];
out[14]= tmp[12] * win_bt[14];
out[15]= tmp[11] * win_bt[15];
out[16]= tmp[10] * win_bt[16];
out[17]= tmp[9] * win_bt[17];
out[18]= tmp[8] * win_bt[18];
out[19]= tmp[7] * win_bt[19];
out[20]= tmp[6] * win_bt[20];
out[21]= tmp[5] * win_bt[21];
out[22]= tmp[4] * win_bt[22];
out[23]= tmp[3] * win_bt[23];
out[24]= tmp[2] * win_bt[24];
out[25]= tmp[1] * win_bt[25];
out[26]= tmp[0] * win_bt[26];
out[27]= tmp[0] * win_bt[27];
out[28]= tmp[1] * win_bt[28];
out[29]= tmp[2] * win_bt[29];
out[30]= tmp[3] * win_bt[30];
out[31]= tmp[4] * win_bt[31];
out[32]= tmp[5] * win_bt[32];
out[33]= tmp[6] * win_bt[33];
out[34]= tmp[7] * win_bt[34];
out[35]= tmp[8] * win_bt[35];
}
}
#ifdef COOLPRO
#pragma optimize("",on) // Restore optimizations for VC 5.0
#endif⌨️ 快捷键说明
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