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Allowing fractional bits for splitting angle (theta)

--- a/libcelt/bands.c

+++ b/libcelt/bands.c

@@ -524,6 +524,35 @@

       }

 }

+static int compute_qn(int N, int b, int offset, int stereo)

+{

+   static const celt_int16 exp2_table8[8] =

+      {16384, 17867, 19484, 21247, 23170, 25268, 27554, 30048};

+   int qn, qb;

+   int N2 = 2*N-1;

+   if (stereo && N==2)

+      N2--;

+   qb = (b+N2*offset)/(N2);

+   if (qb > (b>>1)-(1<<BITRES))

+      qb = (b>>1)-(1<<BITRES);

+

+   if (qb<0)

+       qb = 0;

+   if (qb>14<<BITRES)

+     qb = 14<<BITRES;

+

+   if (qb<(1<<BITRES>>1)) {

+      qn = 1;

+   } else {

+      qn = ((1<<(qb>>BITRES))*exp2_table8[qb&0x7] + (1<<14))>>14;

+      qn = qn>>1<<1;

+      if (qn>1024)

+         qn = 1024;

+   }

+   return qn;

+}

+

+

 /* This function is responsible for encoding and decoding a band for both

    the mono and stereo case. Even in the mono case, it can split the band

    in two and transmit the energy difference with the two half-bands. It

@@ -637,35 +666,20 @@

    if (split)

    {

-      int qb, qn;

+      int qn;

       int itheta=0;

       int mbits, sbits, delta;

       int qalloc;

       celt_word16 mid, side;

-      int offset, N2;

-      offset = ((m->logN[i]+(LM<<BITRES))>>1) - (stereo ? QTHETA_OFFSET_STEREO : QTHETA_OFFSET);

+      int offset;

       /* Decide on the resolution to give to the split parameter theta */

-      N2 = 2*N-1;

-      if (stereo && N==2)

-         N2--;

-      qb = (b+N2*offset)/(N2);

-      if (qb > (b>>1)-(1<<BITRES))

-         qb = (b>>1)-(1<<BITRES);

+      offset = ((m->logN[i]+(LM<<BITRES))>>1) - (stereo ? QTHETA_OFFSET_STEREO : QTHETA_OFFSET);

+      qn = compute_qn(N, b, offset, stereo);

-      if (qb<0)

-          qb = 0;

-      if (qb>14<<BITRES)

-        qb = 14<<BITRES;

-

-      qb >>= BITRES;

-      qn = 1<<qb;

-

       qalloc = 0;

       if (qn!=1)

       {

-         int shift=14-qb;

-

          if (encode)

          {

             if (stereo)

@@ -685,7 +699,7 @@

             itheta = floor(.5f+16384*0.63662f*atan2(side,mid));

    #endif

-            itheta = (itheta+(1<<shift>>1))>>shift;

+            itheta = (itheta*qn+8192)>>14;

          }

          /* Entropy coding of the angle. We use a uniform pdf for the

@@ -732,7 +746,7 @@

             }

             qalloc = log2_frac(ft,BITRES) - log2_frac(fs,BITRES) + 1;

          }

-         itheta <<= shift;

+         itheta = itheta*16384/qn;

       } else {

          if (stereo && encode)

             stereo_band_mix(m, X, Y, bandE, 1, i, 1, N);

--- a/libcelt/rate.h

+++ b/libcelt/rate.h

@@ -36,7 +36,7 @@

 #define MAX_PSEUDO 40

 #define LOG_MAX_PSEUDO 6

-#define MAX_PULSES 128

+#define MAX_PULSES 256

 #define LOG_MAX_PULSES 7

 #define BITRES 3

@@ -61,26 +61,6 @@

    lo = 0;

    hi = MAX_PSEUDO-1;

    for (i=0;i<LOG_MAX_PSEUDO;i++)

-   {

-      int mid = (lo+hi)>>1;

-      /* OPT: Make sure this is implemented with a conditional move */

-      if (cache[mid] >= bits)

-         hi = mid;

-      else

-         lo = mid;

-   }

-   if (bits-cache[lo] <= cache[hi]-bits)

-      return lo;

-   else

-      return hi;

-   

-   lo = 0;

-   hi = MAX_PULSES-1;

-   

-   /* Instead of using the "bisection condition" we use a fixed number of 

-   iterations because it should be faster */

-   /*while (hi-lo != 1)*/

-   for (i=0;i<LOG_MAX_PULSES;i++)

    {

       int mid = (lo+hi)>>1;

       /* OPT: Make sure this is implemented with a conditional move */