Remove Opus from DEPS and import a local copy

third_party/opus/src/celt/celt_decoder.c

+/* Copyright (c) 2007-2008 CSIRO
+   Copyright (c) 2007-2010 Xiph.Org Foundation
+   Copyright (c) 2008 Gregory Maxwell
+   Written by Jean-Marc Valin and Gregory Maxwell */
+/*
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+
+   - Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+   - Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#define CELT_DECODER_C
+
+#include "cpu_support.h"
+#include "os_support.h"
+#include "mdct.h"
+#include <math.h>
+#include "celt.h"
+#include "pitch.h"
+#include "bands.h"
+#include "modes.h"
+#include "entcode.h"
+#include "quant_bands.h"
+#include "rate.h"
+#include "stack_alloc.h"
+#include "mathops.h"
+#include "float_cast.h"
+#include <stdarg.h>
+#include "celt_lpc.h"
+#include "vq.h"
+
+#if defined(SMALL_FOOTPRINT) && defined(FIXED_POINT)
+#define NORM_ALIASING_HACK
+#endif
+/**********************************************************************/
+/*                                                                    */
+/*                             DECODER                                */
+/*                                                                    */
+/**********************************************************************/
+#define DECODE_BUFFER_SIZE 2048
+
+/** Decoder state
+ @brief Decoder state
+ */
+struct OpusCustomDecoder {
+   const OpusCustomMode *mode;
+   int overlap;
+   int channels;
+   int stream_channels;
+
+   int downsample;
+   int start, end;
+   int signalling;
+   int arch;
+
+   /* Everything beyond this point gets cleared on a reset */
+#define DECODER_RESET_START rng
+
+   opus_uint32 rng;
+   int error;
+   int last_pitch_index;
+   int loss_count;
+   int skip_plc;
+   int postfilter_period;
+   int postfilter_period_old;
+   opus_val16 postfilter_gain;
+   opus_val16 postfilter_gain_old;
+   int postfilter_tapset;
+   int postfilter_tapset_old;
+
+   celt_sig preemph_memD[2];
+
+   celt_sig _decode_mem[1]; /* Size = channels*(DECODE_BUFFER_SIZE+mode->overlap) */
+   /* opus_val16 lpc[],  Size = channels*LPC_ORDER */
+   /* opus_val16 oldEBands[], Size = 2*mode->nbEBands */
+   /* opus_val16 oldLogE[], Size = 2*mode->nbEBands */
+   /* opus_val16 oldLogE2[], Size = 2*mode->nbEBands */
+   /* opus_val16 backgroundLogE[], Size = 2*mode->nbEBands */
+};
+
+int celt_decoder_get_size(int channels)
+{
+   const CELTMode *mode = opus_custom_mode_create(48000, 960, NULL);
+   return opus_custom_decoder_get_size(mode, channels);
+}
+
+OPUS_CUSTOM_NOSTATIC int opus_custom_decoder_get_size(const CELTMode *mode, int channels)
+{
+   int size = sizeof(struct CELTDecoder)
+            + (channels*(DECODE_BUFFER_SIZE+mode->overlap)-1)*sizeof(celt_sig)
+            + channels*LPC_ORDER*sizeof(opus_val16)
+            + 4*2*mode->nbEBands*sizeof(opus_val16);
+   return size;
+}
+
+#ifdef CUSTOM_MODES
+CELTDecoder *opus_custom_decoder_create(const CELTMode *mode, int channels, int *error)
+{
+   int ret;
+   CELTDecoder *st = (CELTDecoder *)opus_alloc(opus_custom_decoder_get_size(mode, channels));
+   ret = opus_custom_decoder_init(st, mode, channels);
+   if (ret != OPUS_OK)
+   {
+      opus_custom_decoder_destroy(st);
+      st = NULL;
+   }
+   if (error)
+      *error = ret;
+   return st;
+}
+#endif /* CUSTOM_MODES */
+
+int celt_decoder_init(CELTDecoder *st, opus_int32 sampling_rate, int channels)
+{
+   int ret;
+   ret = opus_custom_decoder_init(st, opus_custom_mode_create(48000, 960, NULL), channels);
+   if (ret != OPUS_OK)
+      return ret;
+   st->downsample = resampling_factor(sampling_rate);
+   if (st->downsample==0)
+      return OPUS_BAD_ARG;
+   else
+      return OPUS_OK;
+}
+
+OPUS_CUSTOM_NOSTATIC int opus_custom_decoder_init(CELTDecoder *st, const CELTMode *mode, int channels)
+{
+   if (channels < 0 || channels > 2)
+      return OPUS_BAD_ARG;
+
+   if (st==NULL)
+      return OPUS_ALLOC_FAIL;
+
+   OPUS_CLEAR((char*)st, opus_custom_decoder_get_size(mode, channels));
+
+   st->mode = mode;
+   st->overlap = mode->overlap;
+   st->stream_channels = st->channels = channels;
+
+   st->downsample = 1;
+   st->start = 0;
+   st->end = st->mode->effEBands;
+   st->signalling = 1;
+   st->arch = opus_select_arch();
+
+   opus_custom_decoder_ctl(st, OPUS_RESET_STATE);
+
+   return OPUS_OK;
+}
+
+#ifdef CUSTOM_MODES
+void opus_custom_decoder_destroy(CELTDecoder *st)
+{
+   opus_free(st);
+}
+#endif /* CUSTOM_MODES */
+
+
+#ifndef RESYNTH
+static
+#endif
+void deemphasis(celt_sig *in[], opus_val16 *pcm, int N, int C, int downsample, const opus_val16 *coef,
+      celt_sig *mem, int accum)
+{
+   int c;
+   int Nd;
+   int apply_downsampling=0;
+   opus_val16 coef0;
+   VARDECL(celt_sig, scratch);
+   SAVE_STACK;
+#ifndef FIXED_POINT
+   (void)accum;
+   celt_assert(accum==0);
+#endif
+   ALLOC(scratch, N, celt_sig);
+   coef0 = coef[0];
+   Nd = N/downsample;
+   c=0; do {
+      int j;
+      celt_sig * OPUS_RESTRICT x;
+      opus_val16  * OPUS_RESTRICT y;
+      celt_sig m = mem[c];
+      x =in[c];
+      y = pcm+c;
+#ifdef CUSTOM_MODES
+      if (coef[1] != 0)
+      {
+         opus_val16 coef1 = coef[1];
+         opus_val16 coef3 = coef[3];
+         for (j=0;j<N;j++)
+         {
+            celt_sig tmp = x[j] + m + VERY_SMALL;
+            m = MULT16_32_Q15(coef0, tmp)
+                          - MULT16_32_Q15(coef1, x[j]);
+            tmp = SHL32(MULT16_32_Q15(coef3, tmp), 2);
+            scratch[j] = tmp;
+         }
+         apply_downsampling=1;
+      } else
+#endif
+      if (downsample>1)
+      {
+         /* Shortcut for the standard (non-custom modes) case */
+         for (j=0;j<N;j++)
+         {
+            celt_sig tmp = x[j] + m + VERY_SMALL;
+            m = MULT16_32_Q15(coef0, tmp);
+            scratch[j] = tmp;
+         }
+         apply_downsampling=1;
+      } else {
+         /* Shortcut for the standard (non-custom modes) case */
+#ifdef FIXED_POINT
+         if (accum)
+         {
+            for (j=0;j<N;j++)
+            {
+               celt_sig tmp = x[j] + m + VERY_SMALL;
+               m = MULT16_32_Q15(coef0, tmp);
+               y[j*C] = SAT16(ADD32(y[j*C], SCALEOUT(SIG2WORD16(tmp))));
+            }
+         } else
+#endif
+         {
+            for (j=0;j<N;j++)
+            {
+               celt_sig tmp = x[j] + m + VERY_SMALL;
+               m = MULT16_32_Q15(coef0, tmp);
+               y[j*C] = SCALEOUT(SIG2WORD16(tmp));
+            }
+         }
+      }
+      mem[c] = m;
+
+      if (apply_downsampling)
+      {
+         /* Perform down-sampling */
+#ifdef FIXED_POINT
+         if (accum)
+         {
+            for (j=0;j<Nd;j++)
+               y[j*C] = SAT16(ADD32(y[j*C], SCALEOUT(SIG2WORD16(scratch[j*downsample]))));
+         } else
+#endif
+         {
+            for (j=0;j<Nd;j++)
+               y[j*C] = SCALEOUT(SIG2WORD16(scratch[j*downsample]));
+         }
+      }
+   } while (++c<C);
+   RESTORE_STACK;
+}
+
+#ifndef RESYNTH
+static
+#endif
+void celt_synthesis(const CELTMode *mode, celt_norm *X, celt_sig * out_syn[],
+                    opus_val16 *oldBandE, int start, int effEnd, int C, int CC,
+                    int isTransient, int LM, int downsample,
+                    int silence, int arch)
+{
+   int c, i;
+   int M;
+   int b;
+   int B;
+   int N, NB;
+   int shift;
+   int nbEBands;
+   int overlap;
+   VARDECL(celt_sig, freq);
+   SAVE_STACK;
+
+   overlap = mode->overlap;
+   nbEBands = mode->nbEBands;
+   N = mode->shortMdctSize<<LM;
+   ALLOC(freq, N, celt_sig); /**< Interleaved signal MDCTs */
+   M = 1<<LM;
+
+   if (isTransient)
+   {
+      B = M;
+      NB = mode->shortMdctSize;
+      shift = mode->maxLM;
+   } else {
+      B = 1;
+      NB = mode->shortMdctSize<<LM;
+      shift = mode->maxLM-LM;
+   }
+
+   if (CC==2&&C==1)
+   {
+      /* Copying a mono streams to two channels */
+      celt_sig *freq2;
+      denormalise_bands(mode, X, freq, oldBandE, start, effEnd, M,
+            downsample, silence);
+      /* Store a temporary copy in the output buffer because the IMDCT destroys its input. */
+      freq2 = out_syn[1]+overlap/2;
+      OPUS_COPY(freq2, freq, N);
+      for (b=0;b<B;b++)
+         clt_mdct_backward(&mode->mdct, &freq2[b], out_syn[0]+NB*b, mode->window, overlap, shift, B, arch);
+      for (b=0;b<B;b++)
+         clt_mdct_backward(&mode->mdct, &freq[b], out_syn[1]+NB*b, mode->window, overlap, shift, B, arch);
+   } else if (CC==1&&C==2)
+   {
+      /* Downmixing a stereo stream to mono */
+      celt_sig *freq2;
+      freq2 = out_syn[0]+overlap/2;
+      denormalise_bands(mode, X, freq, oldBandE, start, effEnd, M,
+            downsample, silence);
+      /* Use the output buffer as temp array before downmixing. */
+      denormalise_bands(mode, X+N, freq2, oldBandE+nbEBands, start, effEnd, M,
+            downsample, silence);
+      for (i=0;i<N;i++)
+         freq[i] = HALF32(ADD32(freq[i],freq2[i]));
+      for (b=0;b<B;b++)
+         clt_mdct_backward(&mode->mdct, &freq[b], out_syn[0]+NB*b, mode->window, overlap, shift, B, arch);
+   } else {
+      /* Normal case (mono or stereo) */
+      c=0; do {
+         denormalise_bands(mode, X+c*N, freq, oldBandE+c*nbEBands, start, effEnd, M,
+               downsample, silence);
+         for (b=0;b<B;b++)
+            clt_mdct_backward(&mode->mdct, &freq[b], out_syn[c]+NB*b, mode->window, overlap, shift, B, arch);
+      } while (++c<CC);
+   }
+   RESTORE_STACK;
+}
+
+static void tf_decode(int start, int end, int isTransient, int *tf_res, int LM, ec_dec *dec)
+{
+   int i, curr, tf_select;
+   int tf_select_rsv;
+   int tf_changed;
+   int logp;
+   opus_uint32 budget;
+   opus_uint32 tell;
+
+   budget = dec->storage*8;
+   tell = ec_tell(dec);
+   logp = isTransient ? 2 : 4;
+   tf_select_rsv = LM>0 && tell+logp+1<=budget;
+   budget -= tf_select_rsv;
+   tf_changed = curr = 0;
+   for (i=start;i<end;i++)
+   {
+      if (tell+logp<=budget)
+      {
+         curr ^= ec_dec_bit_logp(dec, logp);
+         tell = ec_tell(dec);
+         tf_changed |= curr;
+      }
+      tf_res[i] = curr;
+      logp = isTransient ? 4 : 5;
+   }
+   tf_select = 0;
+   if (tf_select_rsv &&
+     tf_select_table[LM][4*isTransient+0+tf_changed] !=
+     tf_select_table[LM][4*isTransient+2+tf_changed])
+   {
+      tf_select = ec_dec_bit_logp(dec, 1);
+   }
+   for (i=start;i<end;i++)
+   {
+      tf_res[i] = tf_select_table[LM][4*isTransient+2*tf_select+tf_res[i]];
+   }
+}
+
+/* The maximum pitch lag to allow in the pitch-based PLC. It's possible to save
+   CPU time in the PLC pitch search by making this smaller than MAX_PERIOD. The
+   current value corresponds to a pitch of 66.67 Hz. */
+#define PLC_PITCH_LAG_MAX (720)
+/* The minimum pitch lag to allow in the pitch-based PLC. This corresponds to a
+   pitch of 480 Hz. */
+#define PLC_PITCH_LAG_MIN (100)
+
+static int celt_plc_pitch_search(celt_sig *decode_mem[2], int C, int arch)
+{
+   int pitch_index;
+   VARDECL( opus_val16, lp_pitch_buf );
+   SAVE_STACK;
+   ALLOC( lp_pitch_buf, DECODE_BUFFER_SIZE>>1, opus_val16 );
+   pitch_downsample(decode_mem, lp_pitch_buf,
+         DECODE_BUFFER_SIZE, C, arch);
+   pitch_search(lp_pitch_buf+(PLC_PITCH_LAG_MAX>>1), lp_pitch_buf,
+         DECODE_BUFFER_SIZE-PLC_PITCH_LAG_MAX,
+         PLC_PITCH_LAG_MAX-PLC_PITCH_LAG_MIN, &pitch_index, arch);
+   pitch_index = PLC_PITCH_LAG_MAX-pitch_index;
+   RESTORE_STACK;
+   return pitch_index;
+}
+
+static void celt_decode_lost(CELTDecoder * OPUS_RESTRICT st, int N, int LM)
+{
+   int c;
+   int i;
+   const int C = st->channels;
+   celt_sig *decode_mem[2];
+   celt_sig *out_syn[2];
+   opus_val16 *lpc;
+   opus_val16 *oldBandE, *oldLogE, *oldLogE2, *backgroundLogE;
+   const OpusCustomMode *mode;
+   int nbEBands;
+   int overlap;
+   int start;
+   int loss_count;
+   int noise_based;
+   const opus_int16 *eBands;
+   SAVE_STACK;
+
+   mode = st->mode;
+   nbEBands = mode->nbEBands;
+   overlap = mode->overlap;
+   eBands = mode->eBands;
+
+   c=0; do {
+      decode_mem[c] = st->_decode_mem + c*(DECODE_BUFFER_SIZE+overlap);
+      out_syn[c] = decode_mem[c]+DECODE_BUFFER_SIZE-N;
+   } while (++c<C);
+   lpc = (opus_val16*)(st->_decode_mem+(DECODE_BUFFER_SIZE+overlap)*C);
+   oldBandE = lpc+C*LPC_ORDER;
+   oldLogE = oldBandE + 2*nbEBands;
+   oldLogE2 = oldLogE + 2*nbEBands;
+   backgroundLogE = oldLogE2  + 2*nbEBands;
+
+   loss_count = st->loss_count;
+   start = st->start;
+   noise_based = loss_count >= 5 || start != 0 || st->skip_plc;
+   if (noise_based)
+   {
+      /* Noise-based PLC/CNG */
+#ifdef NORM_ALIASING_HACK
+      celt_norm *X;
+#else
+      VARDECL(celt_norm, X);
+#endif
+      opus_uint32 seed;
+      int end;
+      int effEnd;
+      opus_val16 decay;
+      end = st->end;
+      effEnd = IMAX(start, IMIN(end, mode->effEBands));
+
+#ifdef NORM_ALIASING_HACK
+      /* This is an ugly hack that breaks aliasing rules and would be easily broken,
+         but it saves almost 4kB of stack. */
+      X = (celt_norm*)(out_syn[C-1]+overlap/2);
+#else
+      ALLOC(X, C*N, celt_norm);   /**< Interleaved normalised MDCTs */
+#endif
+
+      /* Energy decay */
+      decay = loss_count==0 ? QCONST16(1.5f, DB_SHIFT) : QCONST16(.5f, DB_SHIFT);
+      c=0; do
+      {
+         for (i=start;i<end;i++)
+            oldBandE[c*nbEBands+i] = MAX16(backgroundLogE[c*nbEBands+i], oldBandE[c*nbEBands+i] - decay);
+      } while (++c<C);
+      seed = st->rng;
+      for (c=0;c<C;c++)
+      {
+         for (i=start;i<effEnd;i++)
+         {
+            int j;
+            int boffs;
+            int blen;
+            boffs = N*c+(eBands[i]<<LM);
+            blen = (eBands[i+1]-eBands[i])<<LM;
+            for (j=0;j<blen;j++)
+            {
+               seed = celt_lcg_rand(seed);
+               X[boffs+j] = (celt_norm)((opus_int32)seed>>20);
+            }
+            renormalise_vector(X+boffs, blen, Q15ONE, st->arch);
+         }
+      }
+      st->rng = seed;
+
+      c=0; do {
+         OPUS_MOVE(decode_mem[c], decode_mem[c]+N,
+               DECODE_BUFFER_SIZE-N+(overlap>>1));
+      } while (++c<C);
+
+      celt_synthesis(mode, X, out_syn, oldBandE, start, effEnd, C, C, 0, LM, st->downsample, 0, st->arch);
+   } else {
+      /* Pitch-based PLC */
+      const opus_val16 *window;
+      opus_val16 fade = Q15ONE;
+      int pitch_index;
+      VARDECL(opus_val32, etmp);
+      VARDECL(opus_val16, exc);
+
+      if (loss_count == 0)
+      {
+         st->last_pitch_index = pitch_index = celt_plc_pitch_search(decode_mem, C, st->arch);
+      } else {
+         pitch_index = st->last_pitch_index;
+         fade = QCONST16(.8f,15);
+      }
+
+      ALLOC(etmp, overlap, opus_val32);
+      ALLOC(exc, MAX_PERIOD, opus_val16);
+      window = mode->window;
+      c=0; do {
+         opus_val16 decay;
+         opus_val16 attenuation;
+         opus_val32 S1=0;
+         celt_sig *buf;
+         int extrapolation_offset;
+         int extrapolation_len;
+         int exc_length;
+         int j;
+
+         buf = decode_mem[c];
+         for (i=0;i<MAX_PERIOD;i++) {
+            exc[i] = ROUND16(buf[DECODE_BUFFER_SIZE-MAX_PERIOD+i], SIG_SHIFT);
+         }
+
+         if (loss_count == 0)
+         {
+            opus_val32 ac[LPC_ORDER+1];
+            /* Compute LPC coefficients for the last MAX_PERIOD samples before
+               the first loss so we can work in the excitation-filter domain. */
+            _celt_autocorr(exc, ac, window, overlap,
+                   LPC_ORDER, MAX_PERIOD, st->arch);
+            /* Add a noise floor of -40 dB. */
+#ifdef FIXED_POINT
+            ac[0] += SHR32(ac[0],13);
+#else
+            ac[0] *= 1.0001f;
+#endif
+            /* Use lag windowing to stabilize the Levinson-Durbin recursion. */
+            for (i=1;i<=LPC_ORDER;i++)
+            {
+               /*ac[i] *= exp(-.5*(2*M_PI*.002*i)*(2*M_PI*.002*i));*/
+#ifdef FIXED_POINT
+               ac[i] -= MULT16_32_Q15(2*i*i, ac[i]);
+#else
+               ac[i] -= ac[i]*(0.008f*0.008f)*i*i;
+#endif
+            }
+            _celt_lpc(lpc+c*LPC_ORDER, ac, LPC_ORDER);
+         }
+         /* We want the excitation for 2 pitch periods in order to look for a
+            decaying signal, but we can't get more than MAX_PERIOD. */
+         exc_length = IMIN(2*pitch_index, MAX_PERIOD);
+         /* Initialize the LPC history with the samples just before the start
+            of the region for which we're computing the excitation. */
+         {
+            opus_val16 lpc_mem[LPC_ORDER];
+            for (i=0;i<LPC_ORDER;i++)
+            {
+               lpc_mem[i] =
+                     ROUND16(buf[DECODE_BUFFER_SIZE-exc_length-1-i], SIG_SHIFT);
+            }
+            /* Compute the excitation for exc_length samples before the loss. */
+            celt_fir(exc+MAX_PERIOD-exc_length, lpc+c*LPC_ORDER,
+                  exc+MAX_PERIOD-exc_length, exc_length, LPC_ORDER, lpc_mem, st->arch);
+         }
+
+         /* Check if the waveform is decaying, and if so how fast.
+            We do this to avoid adding energy when concealing in a segment
+            with decaying energy. */
+         {
+            opus_val32 E1=1, E2=1;
+            int decay_length;
+#ifdef FIXED_POINT
+            int shift = IMAX(0,2*celt_zlog2(celt_maxabs16(&exc[MAX_PERIOD-exc_length], exc_length))-20);
+#endif
+            decay_length = exc_length>>1;
+            for (i=0;i<decay_length;i++)
+            {
+               opus_val16 e;
+               e = exc[MAX_PERIOD-decay_length+i];
+               E1 += SHR32(MULT16_16(e, e), shift);
+               e = exc[MAX_PERIOD-2*decay_length+i];
+               E2 += SHR32(MULT16_16(e, e), shift);
+            }
+            E1 = MIN32(E1, E2);
+            decay = celt_sqrt(frac_div32(SHR32(E1, 1), E2));
+         }
+
+         /* Move the decoder memory one frame to the left to give us room to
+            add the data for the new frame. We ignore the overlap that extends
+            past the end of the buffer, because we aren't going to use it. */
+         OPUS_MOVE(buf, buf+N, DECODE_BUFFER_SIZE-N);
+
+         /* Extrapolate from the end of the excitation with a period of
+            "pitch_index", scaling down each period by an additional factor of
+            "decay". */
+         extrapolation_offset = MAX_PERIOD-pitch_index;
+         /* We need to extrapolate enough samples to cover a complete MDCT
+            window (including overlap/2 samples on both sides). */
+         extrapolation_len = N+overlap;
+         /* We also apply fading if this is not the first loss. */
+         attenuation = MULT16_16_Q15(fade, decay);
+         for (i=j=0;i<extrapolation_len;i++,j++)
+         {
+            opus_val16 tmp;
+            if (j >= pitch_index) {
+               j -= pitch_index;
+               attenuation = MULT16_16_Q15(attenuation, decay);
+            }
+            buf[DECODE_BUFFER_SIZE-N+i] =
+                  SHL32(EXTEND32(MULT16_16_Q15(attenuation,
+                        exc[extrapolation_offset+j])), SIG_SHIFT);
+            /* Compute the energy of the previously decoded signal whose
+               excitation we're copying. */
+            tmp = ROUND16(
+                  buf[DECODE_BUFFER_SIZE-MAX_PERIOD-N+extrapolation_offset+j],
+                  SIG_SHIFT);
+            S1 += SHR32(MULT16_16(tmp, tmp), 8);
+         }
+
+         {
+            opus_val16 lpc_mem[LPC_ORDER];
+            /* Copy the last decoded samples (prior to the overlap region) to
+               synthesis filter memory so we can have a continuous signal. */
+            for (i=0;i<LPC_ORDER;i++)
+               lpc_mem[i] = ROUND16(buf[DECODE_BUFFER_SIZE-N-1-i], SIG_SHIFT);
+            /* Apply the synthesis filter to convert the excitation back into
+               the signal domain. */
+            celt_iir(buf+DECODE_BUFFER_SIZE-N, lpc+c*LPC_ORDER,
+                  buf+DECODE_BUFFER_SIZE-N, extrapolation_len, LPC_ORDER,
+                  lpc_mem, st->arch);
+         }
+
+         /* Check if the synthesis energy is higher than expected, which can
+            happen with the signal changes during our window. If so,
+            attenuate. */
+         {
+            opus_val32 S2=0;
+            for (i=0;i<extrapolation_len;i++)
+            {
+               opus_val16 tmp = ROUND16(buf[DECODE_BUFFER_SIZE-N+i], SIG_SHIFT);
+               S2 += SHR32(MULT16_16(tmp, tmp), 8);
+            }
+            /* This checks for an "explosion" in the synthesis. */
+#ifdef FIXED_POINT
+            if (!(S1 > SHR32(S2,2)))
+#else
+            /* The float test is written this way to catch NaNs in the output
+               of the IIR filter at the same time. */
+            if (!(S1 > 0.2f*S2))
+#endif
+            {
+               for (i=0;i<extrapolation_len;i++)
+                  buf[DECODE_BUFFER_SIZE-N+i] = 0;
+            } else if (S1 < S2)
+            {
+               opus_val16 ratio = celt_sqrt(frac_div32(SHR32(S1,1)+1,S2+1));
+               for (i=0;i<overlap;i++)
+               {
+                  opus_val16 tmp_g = Q15ONE
+                        - MULT16_16_Q15(window[i], Q15ONE-ratio);
+                  buf[DECODE_BUFFER_SIZE-N+i] =
+                        MULT16_32_Q15(tmp_g, buf[DECODE_BUFFER_SIZE-N+i]);
+               }
+               for (i=overlap;i<extrapolation_len;i++)
+               {
+                  buf[DECODE_BUFFER_SIZE-N+i] =
+                        MULT16_32_Q15(ratio, buf[DECODE_BUFFER_SIZE-N+i]);
+               }
+            }
+         }
+
+         /* Apply the pre-filter to the MDCT overlap for the next frame because
+            the post-filter will be re-applied in the decoder after the MDCT
+            overlap. */
+         comb_filter(etmp, buf+DECODE_BUFFER_SIZE,
+              st->postfilter_period, st->postfilter_period, overlap,
+              -st->postfilter_gain, -st->postfilter_gain,
+              st->postfilter_tapset, st->postfilter_tapset, NULL, 0, st->arch);
+
+         /* Simulate TDAC on the concealed audio so that it blends with the
+            MDCT of the next frame. */
+         for (i=0;i<overlap/2;i++)
+         {
+            buf[DECODE_BUFFER_SIZE+i] =
+               MULT16_32_Q15(window[i], etmp[overlap-1-i])
+               + MULT16_32_Q15(window[overlap-i-1], etmp[i]);
+         }
+      } while (++c<C);
+   }
+
+   st->loss_count = loss_count+1;
+
+   RESTORE_STACK;
+}
+
+int celt_decode_with_ec(CELTDecoder * OPUS_RESTRICT st, const unsigned char *data,
+      int len, opus_val16 * OPUS_RESTRICT pcm, int frame_size, ec_dec *dec, int accum)
+{
+   int c, i, N;
+   int spread_decision;
+   opus_int32 bits;
+   ec_dec _dec;
+#ifdef NORM_ALIASING_HACK
+   celt_norm *X;
+#else
+   VARDECL(celt_norm, X);
+#endif
+   VARDECL(int, fine_quant);
+   VARDECL(int, pulses);
+   VARDECL(int, cap);
+   VARDECL(int, offsets);
+   VARDECL(int, fine_priority);
+   VARDECL(int, tf_res);
+   VARDECL(unsigned char, collapse_masks);
+   celt_sig *decode_mem[2];
+   celt_sig *out_syn[2];
+   opus_val16 *lpc;
+   opus_val16 *oldBandE, *oldLogE, *oldLogE2, *backgroundLogE;
+
+   int shortBlocks;
+   int isTransient;
+   int intra_ener;
+   const int CC = st->channels;
+   int LM, M;
+   int start;
+   int end;
+   int effEnd;
+   int codedBands;
+   int alloc_trim;
+   int postfilter_pitch;
+   opus_val16 postfilter_gain;
+   int intensity=0;
+   int dual_stereo=0;
+   opus_int32 total_bits;
+   opus_int32 balance;
+   opus_int32 tell;
+   int dynalloc_logp;
+   int postfilter_tapset;
+   int anti_collapse_rsv;
+   int anti_collapse_on=0;
+   int silence;
+   int C = st->stream_channels;
+   const OpusCustomMode *mode;
+   int nbEBands;
+   int overlap;
+   const opus_int16 *eBands;
+   ALLOC_STACK;
+
+   mode = st->mode;
+   nbEBands = mode->nbEBands;
+   overlap = mode->overlap;
+   eBands = mode->eBands;
+   start = st->start;
+   end = st->end;
+   frame_size *= st->downsample;
+
+   lpc = (opus_val16*)(st->_decode_mem+(DECODE_BUFFER_SIZE+overlap)*CC);
+   oldBandE = lpc+CC*LPC_ORDER;
+   oldLogE = oldBandE + 2*nbEBands;
+   oldLogE2 = oldLogE + 2*nbEBands;
+   backgroundLogE = oldLogE2  + 2*nbEBands;
+
+#ifdef CUSTOM_MODES
+   if (st->signalling && data!=NULL)
+   {
+      int data0=data[0];
+      /* Convert "standard mode" to Opus header */
+      if (mode->Fs==48000 && mode->shortMdctSize==120)
+      {
+         data0 = fromOpus(data0);
+         if (data0<0)
+            return OPUS_INVALID_PACKET;
+      }
+      st->end = end = IMAX(1, mode->effEBands-2*(data0>>5));
+      LM = (data0>>3)&0x3;
+      C = 1 + ((data0>>2)&0x1);
+      data++;
+      len--;
+      if (LM>mode->maxLM)
+         return OPUS_INVALID_PACKET;
+      if (frame_size < mode->shortMdctSize<<LM)
+         return OPUS_BUFFER_TOO_SMALL;
+      else
+         frame_size = mode->shortMdctSize<<LM;
+   } else {
+#else
+   {
+#endif
+      for (LM=0;LM<=mode->maxLM;LM++)
+         if (mode->shortMdctSize<<LM==frame_size)
+            break;
+      if (LM>mode->maxLM)
+         return OPUS_BAD_ARG;
+   }
+   M=1<<LM;
+
+   if (len<0 || len>1275 || pcm==NULL)
+      return OPUS_BAD_ARG;
+
+   N = M*mode->shortMdctSize;
+   c=0; do {
+      decode_mem[c] = st->_decode_mem + c*(DECODE_BUFFER_SIZE+overlap);
+      out_syn[c] = decode_mem[c]+DECODE_BUFFER_SIZE-N;
+   } while (++c<CC);
+
+   effEnd = end;
+   if (effEnd > mode->effEBands)
+      effEnd = mode->effEBands;
+
+   if (data == NULL || len<=1)
+   {
+      celt_decode_lost(st, N, LM);
+      deemphasis(out_syn, pcm, N, CC, st->downsample, mode->preemph, st->preemph_memD, accum);
+      RESTORE_STACK;
+      return frame_size/st->downsample;
+   }
+
+   /* Check if there are at least two packets received consecutively before
+    * turning on the pitch-based PLC */
+   st->skip_plc = st->loss_count != 0;
+
+   if (dec == NULL)
+   {
+      ec_dec_init(&_dec,(unsigned char*)data,len);
+      dec = &_dec;
+   }
+
+   if (C==1)
+   {
+      for (i=0;i<nbEBands;i++)
+         oldBandE[i]=MAX16(oldBandE[i],oldBandE[nbEBands+i]);
+   }
+
+   total_bits = len*8;
+   tell = ec_tell(dec);
+
+   if (tell >= total_bits)
+      silence = 1;
+   else if (tell==1)
+      silence = ec_dec_bit_logp(dec, 15);
+   else
+      silence = 0;
+   if (silence)
+   {
+      /* Pretend we've read all the remaining bits */
+      tell = len*8;
+      dec->nbits_total+=tell-ec_tell(dec);
+   }
+
+   postfilter_gain = 0;
+   postfilter_pitch = 0;
+   postfilter_tapset = 0;
+   if (start==0 && tell+16 <= total_bits)
+   {
+      if(ec_dec_bit_logp(dec, 1))
+      {
+         int qg, octave;
+         octave = ec_dec_uint(dec, 6);
+         postfilter_pitch = (16<<octave)+ec_dec_bits(dec, 4+octave)-1;
+         qg = ec_dec_bits(dec, 3);
+         if (ec_tell(dec)+2<=total_bits)
+            postfilter_tapset = ec_dec_icdf(dec, tapset_icdf, 2);
+         postfilter_gain = QCONST16(.09375f,15)*(qg+1);
+      }
+      tell = ec_tell(dec);
+   }
+
+   if (LM > 0 && tell+3 <= total_bits)
+   {
+      isTransient = ec_dec_bit_logp(dec, 3);
+      tell = ec_tell(dec);
+   }
+   else
+      isTransient = 0;
+
+   if (isTransient)
+      shortBlocks = M;
+   else
+      shortBlocks = 0;
+
+   /* Decode the global flags (first symbols in the stream) */
+   intra_ener = tell+3<=total_bits ? ec_dec_bit_logp(dec, 3) : 0;
+   /* Get band energies */
+   unquant_coarse_energy(mode, start, end, oldBandE,
+         intra_ener, dec, C, LM);
+
+   ALLOC(tf_res, nbEBands, int);
+   tf_decode(start, end, isTransient, tf_res, LM, dec);
+
+   tell = ec_tell(dec);
+   spread_decision = SPREAD_NORMAL;
+   if (tell+4 <= total_bits)
+      spread_decision = ec_dec_icdf(dec, spread_icdf, 5);
+
+   ALLOC(cap, nbEBands, int);
+
+   init_caps(mode,cap,LM,C);
+
+   ALLOC(offsets, nbEBands, int);
+
+   dynalloc_logp = 6;
+   total_bits<<=BITRES;
+   tell = ec_tell_frac(dec);
+   for (i=start;i<end;i++)
+   {
+      int width, quanta;
+      int dynalloc_loop_logp;
+      int boost;
+      width = C*(eBands[i+1]-eBands[i])<<LM;
+      /* quanta is 6 bits, but no more than 1 bit/sample
+         and no less than 1/8 bit/sample */
+      quanta = IMIN(width<<BITRES, IMAX(6<<BITRES, width));
+      dynalloc_loop_logp = dynalloc_logp;
+      boost = 0;
+      while (tell+(dynalloc_loop_logp<<BITRES) < total_bits && boost < cap[i])
+      {
+         int flag;
+         flag = ec_dec_bit_logp(dec, dynalloc_loop_logp);
+         tell = ec_tell_frac(dec);
+         if (!flag)
+            break;
+         boost += quanta;
+         total_bits -= quanta;
+         dynalloc_loop_logp = 1;
+      }
+      offsets[i] = boost;
+      /* Making dynalloc more likely */
+      if (boost>0)
+         dynalloc_logp = IMAX(2, dynalloc_logp-1);
+   }
+
+   ALLOC(fine_quant, nbEBands, int);
+   alloc_trim = tell+(6<<BITRES) <= total_bits ?
+         ec_dec_icdf(dec, trim_icdf, 7) : 5;
+
+   bits = (((opus_int32)len*8)<<BITRES) - ec_tell_frac(dec) - 1;
+   anti_collapse_rsv = isTransient&&LM>=2&&bits>=((LM+2)<<BITRES) ? (1<<BITRES) : 0;
+   bits -= anti_collapse_rsv;
+
+   ALLOC(pulses, nbEBands, int);
+   ALLOC(fine_priority, nbEBands, int);
+
+   codedBands = compute_allocation(mode, start, end, offsets, cap,
+         alloc_trim, &intensity, &dual_stereo, bits, &balance, pulses,
+         fine_quant, fine_priority, C, LM, dec, 0, 0, 0);
+
+   unquant_fine_energy(mode, start, end, oldBandE, fine_quant, dec, C);
+
+   c=0; do {
+      OPUS_MOVE(decode_mem[c], decode_mem[c]+N, DECODE_BUFFER_SIZE-N+overlap/2);
+   } while (++c<CC);
+
+   /* Decode fixed codebook */
+   ALLOC(collapse_masks, C*nbEBands, unsigned char);
+
+#ifdef NORM_ALIASING_HACK
+   /* This is an ugly hack that breaks aliasing rules and would be easily broken,
+      but it saves almost 4kB of stack. */
+   X = (celt_norm*)(out_syn[CC-1]+overlap/2);
+#else
+   ALLOC(X, C*N, celt_norm);   /**< Interleaved normalised MDCTs */
+#endif
+
+   quant_all_bands(0, mode, start, end, X, C==2 ? X+N : NULL, collapse_masks,
+         NULL, pulses, shortBlocks, spread_decision, dual_stereo, intensity, tf_res,
+         len*(8<<BITRES)-anti_collapse_rsv, balance, dec, LM, codedBands, &st->rng, st->arch);
+
+   if (anti_collapse_rsv > 0)
+   {
+      anti_collapse_on = ec_dec_bits(dec, 1);
+   }
+
+   unquant_energy_finalise(mode, start, end, oldBandE,
+         fine_quant, fine_priority, len*8-ec_tell(dec), dec, C);
+
+   if (anti_collapse_on)
+      anti_collapse(mode, X, collapse_masks, LM, C, N,
+            start, end, oldBandE, oldLogE, oldLogE2, pulses, st->rng, st->arch);
+
+   if (silence)
+   {
+      for (i=0;i<C*nbEBands;i++)
+         oldBandE[i] = -QCONST16(28.f,DB_SHIFT);
+   }
+
+   celt_synthesis(mode, X, out_syn, oldBandE, start, effEnd,
+                  C, CC, isTransient, LM, st->downsample, silence, st->arch);
+
+   c=0; do {
+      st->postfilter_period=IMAX(st->postfilter_period, COMBFILTER_MINPERIOD);
+      st->postfilter_period_old=IMAX(st->postfilter_period_old, COMBFILTER_MINPERIOD);
+      comb_filter(out_syn[c], out_syn[c], st->postfilter_period_old, st->postfilter_period, mode->shortMdctSize,
+            st->postfilter_gain_old, st->postfilter_gain, st->postfilter_tapset_old, st->postfilter_tapset,
+            mode->window, overlap, st->arch);
+      if (LM!=0)
+         comb_filter(out_syn[c]+mode->shortMdctSize, out_syn[c]+mode->shortMdctSize, st->postfilter_period, postfilter_pitch, N-mode->shortMdctSize,
+               st->postfilter_gain, postfilter_gain, st->postfilter_tapset, postfilter_tapset,
+               mode->window, overlap, st->arch);
+
+   } while (++c<CC);
+   st->postfilter_period_old = st->postfilter_period;
+   st->postfilter_gain_old = st->postfilter_gain;
+   st->postfilter_tapset_old = st->postfilter_tapset;
+   st->postfilter_period = postfilter_pitch;
+   st->postfilter_gain = postfilter_gain;
+   st->postfilter_tapset = postfilter_tapset;
+   if (LM!=0)
+   {
+      st->postfilter_period_old = st->postfilter_period;
+      st->postfilter_gain_old = st->postfilter_gain;
+      st->postfilter_tapset_old = st->postfilter_tapset;
+   }
+
+   if (C==1)
+      OPUS_COPY(&oldBandE[nbEBands], oldBandE, nbEBands);
+
+   /* In case start or end were to change */
+   if (!isTransient)
+   {
+      opus_val16 max_background_increase;
+      OPUS_COPY(oldLogE2, oldLogE, 2*nbEBands);
+      OPUS_COPY(oldLogE, oldBandE, 2*nbEBands);
+      /* In normal circumstances, we only allow the noise floor to increase by
+         up to 2.4 dB/second, but when we're in DTX, we allow up to 6 dB
+         increase for each update.*/
+      if (st->loss_count < 10)
+         max_background_increase = M*QCONST16(0.001f,DB_SHIFT);
+      else
+         max_background_increase = QCONST16(1.f,DB_SHIFT);
+      for (i=0;i<2*nbEBands;i++)
+         backgroundLogE[i] = MIN16(backgroundLogE[i] + max_background_increase, oldBandE[i]);
+   } else {
+      for (i=0;i<2*nbEBands;i++)
+         oldLogE[i] = MIN16(oldLogE[i], oldBandE[i]);
+   }
+   c=0; do
+   {
+      for (i=0;i<start;i++)
+      {
+         oldBandE[c*nbEBands+i]=0;
+         oldLogE[c*nbEBands+i]=oldLogE2[c*nbEBands+i]=-QCONST16(28.f,DB_SHIFT);
+      }
+      for (i=end;i<nbEBands;i++)
+      {
+         oldBandE[c*nbEBands+i]=0;
+         oldLogE[c*nbEBands+i]=oldLogE2[c*nbEBands+i]=-QCONST16(28.f,DB_SHIFT);
+      }
+   } while (++c<2);
+   st->rng = dec->rng;
+
+   deemphasis(out_syn, pcm, N, CC, st->downsample, mode->preemph, st->preemph_memD, accum);
+   st->loss_count = 0;
+   RESTORE_STACK;
+   if (ec_tell(dec) > 8*len)
+      return OPUS_INTERNAL_ERROR;
+   if(ec_get_error(dec))
+      st->error = 1;
+   return frame_size/st->downsample;
+}
+
+
+#ifdef CUSTOM_MODES
+
+#ifdef FIXED_POINT
+int opus_custom_decode(CELTDecoder * OPUS_RESTRICT st, const unsigned char *data, int len, opus_int16 * OPUS_RESTRICT pcm, int frame_size)
+{
+   return celt_decode_with_ec(st, data, len, pcm, frame_size, NULL, 0);
+}
+
+#ifndef DISABLE_FLOAT_API
+int opus_custom_decode_float(CELTDecoder * OPUS_RESTRICT st, const unsigned char *data, int len, float * OPUS_RESTRICT pcm, int frame_size)
+{
+   int j, ret, C, N;
+   VARDECL(opus_int16, out);
+   ALLOC_STACK;
+
+   if (pcm==NULL)
+      return OPUS_BAD_ARG;
+
+   C = st->channels;
+   N = frame_size;
+
+   ALLOC(out, C*N, opus_int16);
+   ret=celt_decode_with_ec(st, data, len, out, frame_size, NULL, 0);
+   if (ret>0)
+      for (j=0;j<C*ret;j++)
+         pcm[j]=out[j]*(1.f/32768.f);
+
+   RESTORE_STACK;
+   return ret;
+}
+#endif /* DISABLE_FLOAT_API */
+
+#else
+
+int opus_custom_decode_float(CELTDecoder * OPUS_RESTRICT st, const unsigned char *data, int len, float * OPUS_RESTRICT pcm, int frame_size)
+{
+   return celt_decode_with_ec(st, data, len, pcm, frame_size, NULL, 0);
+}
+
+int opus_custom_decode(CELTDecoder * OPUS_RESTRICT st, const unsigned char *data, int len, opus_int16 * OPUS_RESTRICT pcm, int frame_size)
+{
+   int j, ret, C, N;
+   VARDECL(celt_sig, out);
+   ALLOC_STACK;
+
+   if (pcm==NULL)
+      return OPUS_BAD_ARG;
+
+   C = st->channels;
+   N = frame_size;
+   ALLOC(out, C*N, celt_sig);
+
+   ret=celt_decode_with_ec(st, data, len, out, frame_size, NULL, 0);
+
+   if (ret>0)
+      for (j=0;j<C*ret;j++)
+         pcm[j] = FLOAT2INT16 (out[j]);
+
+   RESTORE_STACK;
+   return ret;
+}
+
+#endif
+#endif /* CUSTOM_MODES */
+
+int opus_custom_decoder_ctl(CELTDecoder * OPUS_RESTRICT st, int request, ...)
+{
+   va_list ap;
+
+   va_start(ap, request);
+   switch (request)
+   {
+      case CELT_SET_START_BAND_REQUEST:
+      {
+         opus_int32 value = va_arg(ap, opus_int32);
+         if (value<0 || value>=st->mode->nbEBands)
+            goto bad_arg;
+         st->start = value;
+      }
+      break;
+      case CELT_SET_END_BAND_REQUEST:
+      {
+         opus_int32 value = va_arg(ap, opus_int32);
+         if (value<1 || value>st->mode->nbEBands)
+            goto bad_arg;
+         st->end = value;
+      }
+      break;
+      case CELT_SET_CHANNELS_REQUEST:
+      {
+         opus_int32 value = va_arg(ap, opus_int32);
+         if (value<1 || value>2)
+            goto bad_arg;
+         st->stream_channels = value;
+      }
+      break;
+      case CELT_GET_AND_CLEAR_ERROR_REQUEST:
+      {
+         opus_int32 *value = va_arg(ap, opus_int32*);
+         if (value==NULL)
+            goto bad_arg;
+         *value=st->error;
+         st->error = 0;
+      }
+      break;
+      case OPUS_GET_LOOKAHEAD_REQUEST:
+      {
+         opus_int32 *value = va_arg(ap, opus_int32*);
+         if (value==NULL)
+            goto bad_arg;
+         *value = st->overlap/st->downsample;
+      }
+      break;
+      case OPUS_RESET_STATE:
+      {
+         int i;
+         opus_val16 *lpc, *oldBandE, *oldLogE, *oldLogE2;
+         lpc = (opus_val16*)(st->_decode_mem+(DECODE_BUFFER_SIZE+st->overlap)*st->channels);
+         oldBandE = lpc+st->channels*LPC_ORDER;
+         oldLogE = oldBandE + 2*st->mode->nbEBands;
+         oldLogE2 = oldLogE + 2*st->mode->nbEBands;
+         OPUS_CLEAR((char*)&st->DECODER_RESET_START,
+               opus_custom_decoder_get_size(st->mode, st->channels)-
+               ((char*)&st->DECODER_RESET_START - (char*)st));
+         for (i=0;i<2*st->mode->nbEBands;i++)
+            oldLogE[i]=oldLogE2[i]=-QCONST16(28.f,DB_SHIFT);
+         st->skip_plc = 1;
+      }
+      break;
+      case OPUS_GET_PITCH_REQUEST:
+      {
+         opus_int32 *value = va_arg(ap, opus_int32*);
+         if (value==NULL)
+            goto bad_arg;
+         *value = st->postfilter_period;
+      }
+      break;
+      case CELT_GET_MODE_REQUEST:
+      {
+         const CELTMode ** value = va_arg(ap, const CELTMode**);
+         if (value==0)
+            goto bad_arg;
+         *value=st->mode;
+      }
+      break;
+      case CELT_SET_SIGNALLING_REQUEST:
+      {
+         opus_int32 value = va_arg(ap, opus_int32);
+         st->signalling = value;
+      }
+      break;
+      case OPUS_GET_FINAL_RANGE_REQUEST:
+      {
+         opus_uint32 * value = va_arg(ap, opus_uint32 *);
+         if (value==0)
+            goto bad_arg;
+         *value=st->rng;
+      }
+      break;
+      default:
+         goto bad_request;
+   }
+   va_end(ap);
+   return OPUS_OK;
+bad_arg:
+   va_end(ap);
+   return OPUS_BAD_ARG;
+bad_request:
+      va_end(ap);
+  return OPUS_UNIMPLEMENTED;
+}