shithub: opus

Info  •  Files  •  Log  •  Branches

optimisation: Got rid of the 32-bit mul in find_spectral_pitch()

--- a/libcelt/pitch.c

+++ b/libcelt/pitch.c

@@ -165,16 +165,15 @@

    /* Compute cross-spectrum using the inverse masking curve as weighting */

    for (i=1;i<n2;i++)

    {

-      celt_word16_t n;

-      celt_word32_t tmp;

-      /*printf ("%d %d ", X[2*i]*X[2*i]+X[2*i+1]*X[2*i+1], Y[2*i]*Y[2*i]+Y[2*i+1]*Y[2*i+1]);*/

-      /*n = DIV32_16(Q15ONE,celt_sqrt(EPSILON+curve[i]));*/

-      /*n = ROUND16(celt_rcp(celt_sqrt(EPSILON+curve[i])),16);*/

+      celt_word16_t Xr, Xi, n;

+      /* weight = 1/sqrt(curve) */

       n = celt_rsqrt(EPSILON+curve[i]);

-      /*printf ("%f ", n);*/

-      tmp = X[2*i];

-      X[2*i] = MULT16_32_Q15(n, ADD32(MULT16_16(X[2*i  ],Y[2*i  ]), MULT16_16(X[2*i+1],Y[2*i+1])));

-      X[2*i+1] = MULT16_32_Q15(n, SUB32(MULT16_16(tmp,Y[2*i+1]), MULT16_16(X[2*i+1],Y[2*i  ])));

+      /* Pre-multiply X by n, so we can keep everything in 16 bits */

+      Xr = SHR32(MULT16_16(n, X[2*i  ]),3);

+      Xi = SHR32(MULT16_16(n, X[2*i+1]),3);

+      /* Cross-spectrum between X and conj(Y) */

+      X[2*i]   = ADD16(MULT16_16_Q15(Xr, Y[2*i  ]), MULT16_16_Q15(Xi,Y[2*i+1]));

+      X[2*i+1] = SUB16(MULT16_16_Q15(Xr, Y[2*i+1]), MULT16_16_Q15(Xi,Y[2*i  ]));

    }

    /*printf ("\n");*/

    X[0] = X[1] = 0;