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Terminate the coding of skip bits at the last dynalloc boosted band. Otherwise the bitstream allows non-sensible behavior by the encoder (dynallocing bits into a band and then skipping it). This reduces skip bit overhead by about 2-3% at moderate bitrates with the current encoder.

--- a/libcelt/rate.c

+++ b/libcelt/rate.c

@@ -140,7 +140,7 @@

 #define ALLOC_STEPS 6

-static inline int interp_bits2pulses(const CELTMode *m, int start, int end,

+static inline int interp_bits2pulses(const CELTMode *m, int start, int end, int skip_start,

       const int *bits1, const int *bits2, const int *thresh, int total, int *bits,

       int *ebits, int *fine_priority, int len, int _C, int LM, void *ec, int encode, int prev)

 {

@@ -221,7 +221,7 @@

          This means we won't be using the extra bit we reserved to signal the

           end of manual skipping, but that will get added back in by

           quant_all_bands().*/

-      if (j<=start)

+      if (j<=skip_start)

          break;

       rem = IMAX(left-(m->eBands[j]-m->eBands[start]),0);

       band_width = m->eBands[codedBands]-m->eBands[j];

@@ -363,6 +363,7 @@

    int lo, hi, len, j;

    const int C = CHANNELS(_C);

    int codedBands;

+   int skip_start;

    VARDECL(int, bits1);

    VARDECL(int, bits2);

    VARDECL(int, thresh);

@@ -371,6 +372,7 @@

    total = IMAX(total, 0);

    len = m->nbEBands;

+   skip_start = start;

    ALLOC(bits1, len, int);

    ALLOC(bits2, len, int);

    ALLOC(thresh, len, int);

@@ -424,8 +426,10 @@

       if (bits1[j] < 0)

          bits1[j] = 0;

       bits1[j] += offsets[j];

+      if (offsets[j]>0)

+         skip_start = j;

    }

-   codedBands = interp_bits2pulses(m, start, end, bits1, bits2, thresh,

+   codedBands = interp_bits2pulses(m, start, end, skip_start, bits1, bits2, thresh,

          total, pulses, ebits, fine_priority, len, C, LM, ec, encode, prev);

    RESTORE_STACK;

    return codedBands;