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New fine energy allocation tuning.

Based on 1/2*log2(N)-19/8, but with the 2-bit and 3-bit thresholds
shifted by 2*log2(N)/8 bit and log2(N)/8 bit, respectively.

--- a/libcelt/rate.c

+++ b/libcelt/rate.c

@@ -181,25 +181,19 @@

    {

       int N0, N, den;

       int offset;

-      int fine_offset;

       N0 = m->eBands[j+1]-m->eBands[j];

       N=M*N0;

       /* Compensate for the extra DoF in stereo */

       den=(C*N+ ((C==2 && N>2) ? 1 : 0));

-      if (N0==1)

-         fine_offset = 19;

-      else if (N0<=4)

-         fine_offset = 14;

-      else

-         fine_offset = 12;

-

       /* Offset for the number of fine bits compared to their "fair share" of total/N */

-      offset = N*C*((m->logN[j] + logM - 2*fine_offset)>>1);

+      offset = N*C*(((m->logN[j] + logM)>>1)-FINE_OFFSET);

-      /* Compensate for the prediction gain in stereo */

-      if (C==2)

-         offset -= 1<<BITRES;

+      /* Changing the offset for allocating the second and third fine energy bit */

+      if (bits[j] + offset < den*2<<BITRES)

+         offset += (m->logN[j] + logM)*N*C>>BITRES-1;

+      else if (bits[j] + offset < den*3<<BITRES)

+         offset += (m->logN[j] + logM)*N*C>>BITRES;

       ebits[j] = (bits[j] + offset + (den<<(BITRES-1))) / (den<<BITRES);

--- a/libcelt/rate.h

+++ b/libcelt/rate.h

@@ -40,6 +40,7 @@

 #define LOG_MAX_PULSES 7

 #define BITRES 3

+#define FINE_OFFSET 19

 #define QTHETA_OFFSET 6

 #define QTHETA_OFFSET_STEREO 4