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Adding a special way to code digital silence in two or more bytes

--- a/libcelt/celt.c

+++ b/libcelt/celt.c

@@ -823,6 +823,7 @@

    int pf_on;

    int anti_collapse_rsv;

    int anti_collapse_on=0;

+   int silence=0;

    SAVE_STACK;

    if (nbCompressedBytes<0 || pcm==NULL)

@@ -904,6 +905,7 @@

       pre[0] = _pre;

       pre[1] = _pre + (N+COMBFILTER_MAXPERIOD);

+      silence = 1;

       c=0; do {

          const celt_word16 * restrict pcmp = pcm+c;

          celt_sig * restrict inp = in+c*(N+st->overlap)+st->overlap;

@@ -915,6 +917,7 @@

             *inp = tmp + st->preemph_memE[c];

             st->preemph_memE[c] = MULT16_32_Q15(st->mode->preemph[1], *inp)

                                    - MULT16_32_Q15(st->mode->preemph[0], tmp);

+            silence = silence && *inp == 0;

             inp++;

             pcmp+=C;

          }

@@ -922,8 +925,15 @@

          CELT_COPY(pre[c]+COMBFILTER_MAXPERIOD, in+c*(N+st->overlap)+st->overlap, N);

       } while (++c<C);

+      ec_enc_bit_logp(enc, silence, 15);

+      if (silence)

+      {

+         while (ec_enc_tell(enc,0) < nbCompressedBytes*8)

+            ec_enc_bits(enc, 0, 1);

+         tell = nbCompressedBytes*8;

+      }

 #ifdef ENABLE_POSTFILTER

-      if (nbAvailableBytes>12*C && st->start==0)

+      if (nbAvailableBytes>12*C && st->start==0 && !silence)

       {

          VARDECL(celt_word16, pitch_buf);

          ALLOC(pitch_buf, (COMBFILTER_MAXPERIOD+N)>>1, celt_word16);

@@ -1310,6 +1320,14 @@

       log2Amp(st->mode, st->start, st->end, bandE, oldBandE, C);

+      if (silence)

+      {

+         for (i=0;i<C*st->mode->nbEBands;i++)

+         {

+            bandE[i] = 0;

+            oldBandE[i] = -QCONST16(9.f,DB_SHIFT);

+         }

+      }

 #ifdef MEASURE_NORM_MSE

       measure_norm_mse(st->mode, X, X0, bandE, bandE0, M, N, C);

 #endif

@@ -1399,8 +1417,8 @@

    /* If there's any room left (can only happen for very high rates),

       fill it with zeros */

-   while (ec_enc_tell(enc,0) + 8 <= nbCompressedBytes*8)

-      ec_enc_bits(enc, 0, 8);

+   while (ec_enc_tell(enc,0) < nbCompressedBytes*8)

+      ec_enc_bits(enc, 0, 1);

    ec_enc_done(enc);

    RESTORE_STACK;

@@ -1951,6 +1969,8 @@

    int postfilter_tapset;

    int anti_collapse_rsv;

    int anti_collapse_on=0;

+   int silence;

+

    SAVE_STACK;

    if (pcm==NULL)

@@ -2013,6 +2033,14 @@

    total_bits = len*8;

    tell = ec_dec_tell(dec, 0);

+   silence = ec_dec_bit_logp(dec, 15);

+   if (silence)

+   {

+      while (ec_dec_tell(dec,0) < len*8)

+         ec_dec_bits(dec, 1);

+      tell = len*8;

+   }

+

    postfilter_gain = 0;

    postfilter_pitch = 0;

    postfilter_tapset = 0;

@@ -2131,6 +2159,14 @@

    log2Amp(st->mode, st->start, st->end, bandE, oldBandE, C);

+   if (silence)

+   {

+      for (i=0;i<C*st->mode->nbEBands;i++)

+      {

+         bandE[i] = 0;

+         oldBandE[i] = -QCONST16(9.f,DB_SHIFT);

+      }

+   }

    /* Synthesis */

    denormalise_bands(st->mode, X, freq, bandE, effEnd, C, M);