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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
+
+ }
+}
+
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