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Tuning the folding gain to be higher when there's only one pulse and lower
when there are many pulses.

--- a/doc/ietf/draft-valin-celt-codec.xml

+++ b/doc/ietf/draft-valin-celt-codec.xml

@@ -684,11 +684,7 @@

 </t>

 <t>

-g = N / (N + kf * K),

-</t>

-

-<t>

-where kf = 6. 

+g = N / (N + 2*K*(K+1)),

 </t>

 <t>

--- a/libcelt/vq.c

+++ b/libcelt/vq.c

@@ -360,6 +360,16 @@

    /* Here, we assume that id will never be greater than N0, i.e. that 

       no band is wider than N0. In the unlikely case it happens, we set

       everything to zero */

+   /*{

+	   int offset = (N0*C - (id+C*N))/2;

+	   if (offset > C*N0/16)

+		   offset = C*N0/16;

+	   offset -= offset % (C*B);

+	   if (offset < 0)

+		   offset = 0;

+	   //printf ("%d\n", offset);

+	   id += offset;

+   }*/

    if (id+C*N>N0*C)

       for (j=0;j<C*N;j++)

          P[j] = 0;

@@ -368,8 +378,6 @@

          P[j] = Y[id++];

 }

-#define KGAIN 6

-

 void intra_fold(const CELTMode *m, celt_norm_t * restrict x, int N, int K, celt_norm_t *Y, celt_norm_t * restrict P, int N0, int B)

 {

    celt_word16_t pred_gain;

@@ -378,7 +386,7 @@

    if (K==0)

       pred_gain = Q15ONE;

    else

-      pred_gain = celt_div((celt_word32_t)MULT16_16(Q15_ONE,N),(celt_word32_t)(N+KGAIN*K));

+      pred_gain = celt_div((celt_word32_t)MULT16_16(Q15_ONE,N),(celt_word32_t)(N+2*K*(K+1)));

    fold(m, N, Y, P, N0, B);

    renormalise_vector(P, pred_gain, C*N, 1);