mpv/mp3lib/dct36.c

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/*
// This is an optimized DCT from Jeff Tsay's maplay 1.2+ package.
// Saved one multiplication by doing the 'twiddle factor' stuff
// together with the window mul. (MH)
//
// This uses Byeong Gi Lee's Fast Cosine Transform algorithm, but the
// 9 point IDCT needs to be reduced further. Unfortunately, I don't
// know how to do that, because 9 is not an even number. - Jeff.
//
//////////////////////////////////////////////////////////////////
//
// 9 Point Inverse Discrete Cosine Transform
//
// This piece of code is Copyright 1997 Mikko Tommila and is freely usable
// by anybody. The algorithm itself is of course in the public domain.
//
// Again derived heuristically from the 9-point WFTA.
//
// The algorithm is optimized (?) for speed, not for small rounding errors or
// good readability.
//
// 36 additions, 11 multiplications
//
// Again this is very likely sub-optimal.
//
// The code is optimized to use a minimum number of temporary variables,
// so it should compile quite well even on 8-register Intel x86 processors.
// This makes the code quite obfuscated and very difficult to understand.
//
// References:
// [1] S. Winograd: "On Computing the Discrete Fourier Transform",
// Mathematics of Computation, Volume 32, Number 141, January 1978,
// Pages 175-199
*/
/*------------------------------------------------------------------*/
/* */
/* Function: Calculation of the inverse MDCT */
/* */
/*------------------------------------------------------------------*/
static void dct36(real *inbuf,real *o1,real *o2,real *wintab,real *tsbuf)
{
#ifdef NEW_DCT9
real tmp[18];
#endif
{
register real *in = inbuf;
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];
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];
#ifdef NEW_DCT9
{
real t0, t1, t2, t3, t4, t5, t6, t7;
t1 = COS6_2 * in[12];
t2 = COS6_2 * (in[8] + in[16] - in[4]);
t3 = in[0] + t1;
t4 = in[0] - t1 - t1;
t5 = t4 - t2;
t0 = cos9[0] * (in[4] + in[8]);
t1 = cos9[1] * (in[8] - in[16]);
tmp[4] = t4 + t2 + t2;
t2 = cos9[2] * (in[4] + in[16]);
t6 = t3 - t0 - t2;
t0 += t3 + t1;
t3 += t2 - t1;
t2 = cos18[0] * (in[2] + in[10]);
t4 = cos18[1] * (in[10] - in[14]);
t7 = COS6_1 * in[6];
t1 = t2 + t4 + t7;
tmp[0] = t0 + t1;
tmp[8] = t0 - t1;
t1 = cos18[2] * (in[2] + in[14]);
t2 += t1 - t7;
tmp[3] = t3 + t2;
t0 = COS6_1 * (in[10] + in[14] - in[2]);
tmp[5] = t3 - t2;
t4 -= t1 + t7;
tmp[1] = t5 - t0;
tmp[7] = t5 + t0;
tmp[2] = t6 + t4;
tmp[6] = t6 - t4;
}
{
real t0, t1, t2, t3, t4, t5, t6, t7;
t1 = COS6_2 * in[13];
t2 = COS6_2 * (in[9] + in[17] - in[5]);
t3 = in[1] + t1;
t4 = in[1] - t1 - t1;
t5 = t4 - t2;
t0 = cos9[0] * (in[5] + in[9]);
t1 = cos9[1] * (in[9] - in[17]);
tmp[13] = (t4 + t2 + t2) * tfcos36[17-13];
t2 = cos9[2] * (in[5] + in[17]);
t6 = t3 - t0 - t2;
t0 += t3 + t1;
t3 += t2 - t1;
t2 = cos18[0] * (in[3] + in[11]);
t4 = cos18[1] * (in[11] - in[15]);
t7 = COS6_1 * in[7];
t1 = t2 + t4 + t7;
tmp[17] = (t0 + t1) * tfcos36[17-17];
tmp[9] = (t0 - t1) * tfcos36[17-9];
t1 = cos18[2] * (in[3] + in[15]);
t2 += t1 - t7;
tmp[14] = (t3 + t2) * tfcos36[17-14];
t0 = COS6_1 * (in[11] + in[15] - in[3]);
tmp[12] = (t3 - t2) * tfcos36[17-12];
t4 -= t1 + t7;
tmp[16] = (t5 - t0) * tfcos36[17-16];
tmp[10] = (t5 + t0) * tfcos36[17-10];
tmp[15] = (t6 + t4) * tfcos36[17-15];
tmp[11] = (t6 - t4) * tfcos36[17-11];
}
#define MACRO(v) { \
real tmpval; \
real sum0 = tmp[(v)]; \
real sum1 = tmp[17-(v)]; \
out2[9+(v)] = (tmpval = sum0 + sum1) * w[27+(v)]; \
out2[8-(v)] = tmpval * w[26-(v)]; \
sum0 -= sum1; \
ts[SBLIMIT*(8-(v))] = out1[8-(v)] + sum0 * w[8-(v)]; \
ts[SBLIMIT*(9+(v))] = out1[9+(v)] + sum0 * w[9+(v)]; }
{
register real *out2 = o2;
register real *w = wintab;
register real *out1 = o1;
register real *ts = tsbuf;
MACRO(0);
MACRO(1);
MACRO(2);
MACRO(3);
MACRO(4);
MACRO(5);
MACRO(6);
MACRO(7);
MACRO(8);
}
#else
{
#define MACRO0(v) { \
real tmp; \
out2[9+(v)] = (tmp = sum0 + sum1) * w[27+(v)]; \
out2[8-(v)] = tmp * w[26-(v)]; } \
sum0 -= sum1; \
ts[SBLIMIT*(8-(v))] = out1[8-(v)] + sum0 * w[8-(v)]; \
ts[SBLIMIT*(9+(v))] = out1[9+(v)] + sum0 * w[9+(v)];
#define MACRO1(v) { \
real sum0,sum1; \
sum0 = tmp1a + tmp2a; \
sum1 = (tmp1b + tmp2b) * tfcos36[(v)]; \
MACRO0(v); }
#define MACRO2(v) { \
real sum0,sum1; \
sum0 = tmp2a - tmp1a; \
sum1 = (tmp2b - tmp1b) * tfcos36[(v)]; \
MACRO0(v); }
register const real *c = nCOS9;
register real *out2 = o2;
register real *w = wintab;
register real *out1 = o1;
register real *ts = tsbuf;
real ta33,ta66,tb33,tb66;
ta33 = in[2*3+0] * c[3];
ta66 = in[2*6+0] * c[6];
tb33 = in[2*3+1] * c[3];
tb66 = in[2*6+1] * c[6];
{
real tmp1a,tmp2a,tmp1b,tmp2b;
tmp1a = in[2*1+0] * c[1] + ta33 + in[2*5+0] * c[5] + in[2*7+0] * c[7];
tmp1b = in[2*1+1] * c[1] + tb33 + in[2*5+1] * c[5] + in[2*7+1] * c[7];
tmp2a = in[2*0+0] + in[2*2+0] * c[2] + in[2*4+0] * c[4] + ta66 + in[2*8+0] * c[8];
tmp2b = in[2*0+1] + in[2*2+1] * c[2] + in[2*4+1] * c[4] + tb66 + in[2*8+1] * c[8];
MACRO1(0);
MACRO2(8);
}
{
real tmp1a,tmp2a,tmp1b,tmp2b;
tmp1a = ( in[2*1+0] - in[2*5+0] - in[2*7+0] ) * c[3];
tmp1b = ( in[2*1+1] - in[2*5+1] - in[2*7+1] ) * c[3];
tmp2a = ( in[2*2+0] - in[2*4+0] - in[2*8+0] ) * c[6] - in[2*6+0] + in[2*0+0];
tmp2b = ( in[2*2+1] - in[2*4+1] - in[2*8+1] ) * c[6] - in[2*6+1] + in[2*0+1];
MACRO1(1);
MACRO2(7);
}
{
real tmp1a,tmp2a,tmp1b,tmp2b;
tmp1a = in[2*1+0] * c[5] - ta33 - in[2*5+0] * c[7] + in[2*7+0] * c[1];
tmp1b = in[2*1+1] * c[5] - tb33 - in[2*5+1] * c[7] + in[2*7+1] * c[1];
tmp2a = in[2*0+0] - in[2*2+0] * c[8] - in[2*4+0] * c[2] + ta66 + in[2*8+0] * c[4];
tmp2b = in[2*0+1] - in[2*2+1] * c[8] - in[2*4+1] * c[2] + tb66 + in[2*8+1] * c[4];
MACRO1(2);
MACRO2(6);
}
{
real tmp1a,tmp2a,tmp1b,tmp2b;
tmp1a = in[2*1+0] * c[7] - ta33 + in[2*5+0] * c[1] - in[2*7+0] * c[5];
tmp1b = in[2*1+1] * c[7] - tb33 + in[2*5+1] * c[1] - in[2*7+1] * c[5];
tmp2a = in[2*0+0] - in[2*2+0] * c[4] + in[2*4+0] * c[8] + ta66 - in[2*8+0] * c[2];
tmp2b = in[2*0+1] - in[2*2+1] * c[4] + in[2*4+1] * c[8] + tb66 - in[2*8+1] * c[2];
MACRO1(3);
MACRO2(5);
}
{
real sum0,sum1;
sum0 = in[2*0+0] - in[2*2+0] + in[2*4+0] - in[2*6+0] + in[2*8+0];
sum1 = (in[2*0+1] - in[2*2+1] + in[2*4+1] - in[2*6+1] + in[2*8+1] ) * tfcos36[4];
MACRO0(4);
}
}
#endif
}
}