text: /*
   * Opus encoder
   * Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@gmail.com>
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "encode.h"
  #include "opusenc.h"
  #include "opus_pvq.h"
  #include "opusenc_psy.h"
  #include "opustab.h"
  
  #include "libavutil/channel_layout.h"
  #include "libavutil/float_dsp.h"
  #include "libavutil/mem_internal.h"
  #include "libavutil/opt.h"
  #include "internal.h"
  #include "bytestream.h"
  #include "audio_frame_queue.h"
  
  typedef struct OpusEncContext {
      AVClass *av_class;
      OpusEncOptions options;
      OpusPsyContext psyctx;
      AVCodecContext *avctx;
      AudioFrameQueue afq;
      AVFloatDSPContext *dsp;
      MDCT15Context *mdct[CELT_BLOCK_NB];
      CeltPVQ *pvq;
      struct FFBufQueue bufqueue;
  
      uint8_t enc_id[64];
      int enc_id_bits;
  
      OpusPacketInfo packet;
  
      int channels;
  
      CeltFrame *frame;
      OpusRangeCoder *rc;
  
      /* Actual energy the decoder will have */
      float last_quantized_energy[OPUS_MAX_CHANNELS][CELT_MAX_BANDS];
  
      DECLARE_ALIGNED(32, float, scratch)[2048];
  } OpusEncContext;
  
  static void opus_write_extradata(AVCodecContext *avctx)
  {
      uint8_t *bs = avctx->extradata;
  
      bytestream_put_buffer(&bs, "OpusHead", 8);
      bytestream_put_byte  (&bs, 0x1);
      bytestream_put_byte  (&bs, avctx->channels);
      bytestream_put_le16  (&bs, avctx->initial_padding);
      bytestream_put_le32  (&bs, avctx->sample_rate);
      bytestream_put_le16  (&bs, 0x0);
      bytestream_put_byte  (&bs, 0x0); /* Default layout */
  }
  
  static int opus_gen_toc(OpusEncContext *s, uint8_t *toc, int *size, int *fsize_needed)
  {
      int tmp = 0x0, extended_toc = 0;
      static const int toc_cfg[][OPUS_MODE_NB][OPUS_BANDWITH_NB] = {
          /*  Silk                    Hybrid                  Celt                    Layer     */
          /*  NB  MB  WB SWB  FB      NB  MB  WB SWB  FB      NB  MB  WB SWB  FB      Bandwidth */
          { {  0,  0,  0,  0,  0 }, {  0,  0,  0,  0,  0 }, { 17,  0, 21, 25, 29 } }, /* 2.5 ms */
          { {  0,  0,  0,  0,  0 }, {  0,  0,  0,  0,  0 }, { 18,  0, 22, 26, 30 } }, /*   5 ms */
          { {  1,  5,  9,  0,  0 }, {  0,  0,  0, 13, 15 }, { 19,  0, 23, 27, 31 } }, /*  10 ms */
          { {  2,  6, 10,  0,  0 }, {  0,  0,  0, 14, 16 }, { 20,  0, 24, 28, 32 } }, /*  20 ms */
          { {  3,  7, 11,  0,  0 }, {  0,  0,  0,  0,  0 }, {  0,  0,  0,  0,  0 } }, /*  40 ms */
          { {  4,  8, 12,  0,  0 }, {  0,  0,  0,  0,  0 }, {  0,  0,  0,  0,  0 } }, /*  60 ms */
      };
      int cfg = toc_cfg[s->packet.framesize][s->packet.mode][s->packet.bandwidth];
      *fsize_needed = 0;
      if (!cfg)
          return 1;
      if (s->packet.frames == 2) {                                       /* 2 packets */
          if (s->frame[0].framebits == s->frame[1].framebits) {          /* same size */
              tmp = 0x1;
          } else {                                                  /* different size */
              tmp = 0x2;
              *fsize_needed = 1;                     /* put frame sizes in the packet */
          }
      } else if (s->packet.frames > 2) {
          tmp = 0x3;
          extended_toc = 1;
      }
      tmp |= (s->channels > 1) << 2;                                /* Stereo or mono */
      tmp |= (cfg - 1)         << 3;                           /* codec configuration */
      *toc++ = tmp;
      if (extended_toc) {
          for (int i = 0; i < (s->packet.frames - 1); i++)
              *fsize_needed |= (s->frame[i].framebits != s->frame[i + 1].framebits);
          tmp = (*fsize_needed) << 7;                                /* vbr flag */
          tmp |= (0) << 6;                                       /* padding flag */
          tmp |= s->packet.frames;
          *toc++ = tmp;
      }
      *size = 1 + extended_toc;
      return 0;
  }
  
  static void celt_frame_setup_input(OpusEncContext *s, CeltFrame *f)
  {
      AVFrame *cur = NULL;
      const int subframesize = s->avctx->frame_size;
      int subframes = OPUS_BLOCK_SIZE(s->packet.framesize) / subframesize;
  
      cur = ff_bufqueue_get(&s->bufqueue);
  
      for (int ch = 0; ch < f->channels; ch++) {
          CeltBlock *b = &f->block[ch];
          const void *input = cur->extended_data[ch];
          size_t bps = av_get_bytes_per_sample(cur->format);
          memcpy(b->overlap, input, bps*cur->nb_samples);
      }
  
      av_frame_free(&cur);
  
      for (int sf = 0; sf < subframes; sf++) {
          if (sf != (subframes - 1))
              cur = ff_bufqueue_get(&s->bufqueue);
          else
              cur = ff_bufqueue_peek(&s->bufqueue, 0);
  
          for (int ch = 0; ch < f->channels; ch++) {
              CeltBlock *b = &f->block[ch];
              const void *input = cur->extended_data[ch];
              const size_t bps  = av_get_bytes_per_sample(cur->format);
              const size_t left = (subframesize - cur->nb_samples)*bps;
              const size_t len  = FFMIN(subframesize, cur->nb_samples)*bps;
              memcpy(&b->samples[sf*subframesize], input, len);
              memset(&b->samples[cur->nb_samples], 0, left);
          }
  
          /* Last frame isn't popped off and freed yet - we need it for overlap */
          if (sf != (subframes - 1))
              av_frame_free(&cur);
      }
  }
  
  /* Apply the pre emphasis filter */
  static void celt_apply_preemph_filter(OpusEncContext *s, CeltFrame *f)
  {
      const int subframesize = s->avctx->frame_size;
      const int subframes = OPUS_BLOCK_SIZE(s->packet.framesize) / subframesize;
  
      /* Filter overlap */
      for (int ch = 0; ch < f->channels; ch++) {
          CeltBlock *b = &f->block[ch];
          float m = b->emph_coeff;
          for (int i = 0; i < CELT_OVERLAP; i++) {
              float sample = b->overlap[i];
              b->overlap[i] = sample - m;
              m = sample * CELT_EMPH_COEFF;
          }
          b->emph_coeff = m;
      }
  
      /* Filter the samples but do not update the last subframe's coeff - overlap ^^^ */
      for (int sf = 0; sf < subframes; sf++) {
          for (int ch = 0; ch < f->channels; ch++) {
              CeltBlock *b = &f->block[ch];
              float m = b->emph_coeff;
              for (int i = 0; i < subframesize; i++) {
                  float sample = b->samples[sf*subframesize + i];
                  b->samples[sf*subframesize + i] = sample - m;
                  m = sample * CELT_EMPH_COEFF;
              }
              if (sf != (subframes - 1))
                  b->emph_coeff = m;
          }
      }
  }
  
  /* Create the window and do the mdct */
  static void celt_frame_mdct(OpusEncContext *s, CeltFrame *f)
  {
      float *win = s->scratch, *temp = s->scratch + 1920;
  
      if (f->transient) {
          for (int ch = 0; ch < f->channels; ch++) {
              CeltBlock *b = &f->block[ch];
              float *src1 = b->overlap;
              for (int t = 0; t < f->blocks; t++) {
                  float *src2 = &b->samples[CELT_OVERLAP*t];
                  s->dsp->vector_fmul(win, src1, ff_celt_window, 128);
                  s->dsp->vector_fmul_reverse(&win[CELT_OVERLAP], src2,
                                              ff_celt_window - 8, 128);
                  src1 = src2;
                  s->mdct[0]->mdct(s->mdct[0], b->coeffs + t, win, f->blocks);
              }
          }
      } else {
          int blk_len = OPUS_BLOCK_SIZE(f->size), wlen = OPUS_BLOCK_SIZE(f->size + 1);
          int rwin = blk_len - CELT_OVERLAP, lap_dst = (wlen - blk_len - CELT_OVERLAP) >> 1;
          memset(win, 0, wlen*sizeof(float));
          for (int ch = 0; ch < f->channels; ch++) {
              CeltBlock *b = &f->block[ch];
  
              /* Overlap */
              s->dsp->vector_fmul(temp, b->overlap, ff_celt_window, 128);
              memcpy(win + lap_dst, temp, CELT_OVERLAP*sizeof(float));
  
              /* Samples, flat top window */
              memcpy(&win[lap_dst + CELT_OVERLAP], b->samples, rwin*sizeof(float));
  
              /* Samples, windowed */
              s->dsp->vector_fmul_reverse(temp, b->samples + rwin,
                                          ff_celt_window - 8, 128);
              memcpy(win + lap_dst + blk_len, temp, CELT_OVERLAP*sizeof(float));
  
              s->mdct[f->size]->mdct(s->mdct[f->size], b->coeffs, win, 1);
          }
      }
  
      for (int ch = 0; ch < f->channels; ch++) {
          CeltBlock *block = &f->block[ch];
          for (int i = 0; i < CELT_MAX_BANDS; i++) {
              float ener = 0.0f;
              int band_offset = ff_celt_freq_bands[i] << f->size;
              int band_size   = ff_celt_freq_range[i] << f->size;
              float *coeffs   = &block->coeffs[band_offset];
  
              for (int j = 0; j < band_size; j++)
                  ener += coeffs[j]*coeffs[j];
  
              block->lin_energy[i] = sqrtf(ener) + FLT_EPSILON;
              ener = 1.0f/block->lin_energy[i];
  
              for (int j = 0; j < band_size; j++)
                  coeffs[j] *= ener;
  
              block->energy[i] = log2f(block->lin_energy[i]) - ff_celt_mean_energy[i];
  
              /* CELT_ENERGY_SILENCE is what the decoder uses and its not -infinity */
              block->energy[i] = FFMAX(block->energy[i], CELT_ENERGY_SILENCE);
          }
      }
  }
  
  static void celt_enc_tf(CeltFrame *f, OpusRangeCoder *rc)
  {
      int tf_select = 0, diff = 0, tf_changed = 0, tf_select_needed;
      int bits = f->transient ? 2 : 4;
  
      tf_select_needed = ((f->size && (opus_rc_tell(rc) + bits + 1) <= f->framebits));
  
      for (int i = f->start_band; i < f->end_band; i++) {
          if ((opus_rc_tell(rc) + bits + tf_select_needed) <= f->framebits) {
              const int tbit = (diff ^ 1) == f->tf_change[i];
              ff_opus_rc_enc_log(rc, tbit, bits);
              diff ^= tbit;
              tf_changed |= diff;
          }
          bits = f->transient ? 4 : 5;
      }
  
      if (tf_select_needed && ff_celt_tf_select[f->size][f->transient][0][tf_changed] !=
                              ff_celt_tf_select[f->size][f->transient][1][tf_changed]) {
          ff_opus_rc_enc_log(rc, f->tf_select, 1);
          tf_select = f->tf_select;
      }
  
      for (int i = f->start_band; i < f->end_band; i++)
          f->tf_change[i] = ff_celt_tf_select[f->size][f->transient][tf_select][f->tf_change[i]];
  }
  
  static void celt_enc_quant_pfilter(OpusRangeCoder *rc, CeltFrame *f)
  {
      float gain = f->pf_gain;
      int txval, octave = f->pf_octave, period = f->pf_period, tapset = f->pf_tapset;
  
      ff_opus_rc_enc_log(rc, f->pfilter, 1);
      if (!f->pfilter)
          return;
  
      /* Octave */
      txval = FFMIN(octave, 6);
      ff_opus_rc_enc_uint(rc, txval, 6);
      octave = txval;
      /* Period */
      txval = av_clip(period - (16 << octave) + 1, 0, (1 << (4 + octave)) - 1);
      ff_opus_rc_put_raw(rc, period, 4 + octave);
      period = txval + (16 << octave) - 1;
      /* Gain */
      txval = FFMIN(((int)(gain / 0.09375f)) - 1, 7);
      ff_opus_rc_put_raw(rc, txval, 3);
      gain   = 0.09375f * (txval + 1);
      /* Tapset */
      if ((opus_rc_tell(rc) + 2) <= f->framebits)
          ff_opus_rc_enc_cdf(rc, tapset, ff_celt_model_tapset);
      else
          tapset = 0;
      /* Finally create the coeffs */
      for (int i = 0; i < 2; i++) {
          CeltBlock *block = &f->block[i];
  
          block->pf_period_new = FFMAX(period, CELT_POSTFILTER_MINPERIOD);
          block->pf_gains_new[0] = gain * ff_celt_postfilter_taps[tapset][0];
          block->pf_gains_new[1] = gain * ff_celt_postfilter_taps[tapset][1];
          block->pf_gains_new[2] = gain * ff_celt_postfilter_taps[tapset][2];
      }
  }
  
  static void exp_quant_coarse(OpusRangeCoder *rc, CeltFrame *f,
                               float last_energy[][CELT_MAX_BANDS], int intra)
  {
      float alpha, beta, prev[2] = { 0, 0 };
      const uint8_t *pmod = ff_celt_coarse_energy_dist[f->size][intra];
  
      /* Inter is really just differential coding */
      if (opus_rc_tell(rc) + 3 <= f->framebits)
          ff_opus_rc_enc_log(rc, intra, 3);
      else
          intra = 0;
  
      if (intra) {
          alpha = 0.0f;
          beta  = 1.0f - (4915.0f/32768.0f);
      } else {
          alpha = ff_celt_alpha_coef[f->size];
          beta  = ff_celt_beta_coef[f->size];
      }
  
      for (int i = f->start_band; i < f->end_band; i++) {
          for (int ch = 0; ch < f->channels; ch++) {
              CeltBlock *block = &f->block[ch];
              const int left = f->framebits - opus_rc_tell(rc);
              const float last = FFMAX(-9.0f, last_energy[ch][i]);
              float diff = block->energy[i] - prev[ch] - last*alpha;
              int q_en = lrintf(diff);
              if (left >= 15) {
                  ff_opus_rc_enc_laplace(rc, &q_en, pmod[i << 1] << 7, pmod[(i << 1) + 1] << 6);
              } else if (left >= 2) {
                  q_en = av_clip(q_en, -1, 1);
                  ff_opus_rc_enc_cdf(rc, 2*q_en + 3*(q_en < 0), ff_celt_model_energy_small);
              } else if (left >= 1) {
                  q_en = av_clip(q_en, -1, 0);
                  ff_opus_rc_enc_log(rc, (q_en & 1), 1);
              } else q_en = -1;
  
              block->error_energy[i] = q_en - diff;
              prev[ch] += beta * q_en;
          }
      }
  }
  
  static void celt_quant_coarse(CeltFrame *f, OpusRangeCoder *rc,
                                float last_energy[][CELT_MAX_BANDS])
  {
      uint32_t inter, intra;
      OPUS_RC_CHECKPOINT_SPAWN(rc);
  
      exp_quant_coarse(rc, f, last_energy, 1);
      intra = OPUS_RC_CHECKPOINT_BITS(rc);
  
      OPUS_RC_CHECKPOINT_ROLLBACK(rc);
  
      exp_quant_coarse(rc, f, last_energy, 0);
      inter = OPUS_RC_CHECKPOINT_BITS(rc);
  
      if (inter > intra) { /* Unlikely */
          OPUS_RC_CHECKPOINT_ROLLBACK(rc);
          exp_quant_coarse(rc, f, last_energy, 1);
      }
  }
  
  static void celt_quant_fine(CeltFrame *f, OpusRangeCoder *rc)
  {
      for (int i = f->start_band; i < f->end_band; i++) {
          if (!f->fine_bits[i])
              continue;
          for (int ch = 0; ch < f->channels; ch++) {
              CeltBlock *block = &f->block[ch];
              int quant, lim = (1 << f->fine_bits[i]);
              float offset, diff = 0.5f - block->error_energy[i];
              quant = av_clip(floor(diff*lim), 0, lim - 1);
              ff_opus_rc_put_raw(rc, quant, f->fine_bits[i]);
              offset = 0.5f - ((quant + 0.5f) * (1 << (14 - f->fine_bits[i])) / 16384.0f);
              block->error_energy[i] -= offset;
          }
      }
  }
  
  static void celt_quant_final(OpusEncContext *s, OpusRangeCoder *rc, CeltFrame *f)
  {
      for (int priority = 0; priority < 2; priority++) {
          for (int i = f->start_band; i < f->end_band && (f->framebits - opus_rc_tell(rc)) >= f->channels; i++) {
              if (f->fine_priority[i] != priority || f->fine_bits[i] >= CELT_MAX_FINE_BITS)
                  continue;
              for (int ch = 0; ch < f->channels; ch++) {
                  CeltBlock *block = &f->block[ch];
                  const float err = block->error_energy[i];
                  const float offset = 0.5f * (1 << (14 - f->fine_bits[i] - 1)) / 16384.0f;
                  const int sign = FFABS(err + offset) < FFABS(err - offset);
                  ff_opus_rc_put_raw(rc, sign, 1);
                  block->error_energy[i] -= offset*(1 - 2*sign);
              }
          }
      }
  }
  
  static void celt_encode_frame(OpusEncContext *s, OpusRangeCoder *rc,
                                CeltFrame *f, int index)
  {
      ff_opus_rc_enc_init(rc);
  
      ff_opus_psy_celt_frame_init(&s->psyctx, f, index);
  
      celt_frame_setup_input(s, f);
  
      if (f->silence) {
          if (f->framebits >= 16)
              ff_opus_rc_enc_log(rc, 1, 15); /* Silence (if using explicit singalling) */
          for (int ch = 0; ch < s->channels; ch++)
              memset(s->last_quantized_energy[ch], 0.0f, sizeof(float)*CELT_MAX_BANDS);
          return;
      }
  
      /* Filters */
      celt_apply_preemph_filter(s, f);
      if (f->pfilter) {
          ff_opus_rc_enc_log(rc, 0, 15);
          celt_enc_quant_pfilter(rc, f);
      }
  
      /* Transform */
      celt_frame_mdct(s, f);
  
      /* Need to handle transient/non-transient switches at any point during analysis */
      while (ff_opus_psy_celt_frame_process(&s->psyctx, f, index))
          celt_frame_mdct(s, f);
  
      ff_opus_rc_enc_init(rc);
  
      /* Silence */
      ff_opus_rc_enc_log(rc, 0, 15);
  
      /* Pitch filter */
      if (!f->start_band && opus_rc_tell(rc) + 16 <= f->framebits)
          celt_enc_quant_pfilter(rc, f);
  
      /* Transient flag */
      if (f->size && opus_rc_tell(rc) + 3 <= f->framebits)
          ff_opus_rc_enc_log(rc, f->transient, 3);
  
      /* Main encoding */
      celt_quant_coarse  (f, rc, s->last_quantized_energy);
      celt_enc_tf        (f, rc);
      ff_celt_bitalloc   (f, rc, 1);
      celt_quant_fine    (f, rc);
      ff_celt_quant_bands(f, rc);
  
      /* Anticollapse bit */
      if (f->anticollapse_needed)
          ff_opus_rc_put_raw(rc, f->anticollapse, 1);
  
      /* Final per-band energy adjustments from leftover bits */
      celt_quant_final(s, rc, f);
  
      for (int ch = 0; ch < f->channels; ch++) {
          CeltBlock *block = &f->block[ch];
          for (int i = 0; i < CELT_MAX_BANDS; i++)
              s->last_quantized_energy[ch][i] = block->energy[i] + block->error_energy[i];
      }
  }
  
  static inline int write_opuslacing(uint8_t *dst, int v)
  {
      dst[0] = FFMIN(v - FFALIGN(v - 255, 4), v);
      dst[1] = v - dst[0] >> 2;
      return 1 + (v >= 252);
  }
  
  static void opus_packet_assembler(OpusEncContext *s, AVPacket *avpkt)
  {
      int offset, fsize_needed;
  
      /* Write toc */
      opus_gen_toc(s, avpkt->data, &offset, &fsize_needed);
  
      /* Frame sizes if needed */
      if (fsize_needed) {
          for (int i = 0; i < s->packet.frames - 1; i++) {
              offset += write_opuslacing(avpkt->data + offset,
                                         s->frame[i].framebits >> 3);
          }
      }
  
      /* Packets */
      for (int i = 0; i < s->packet.frames; i++) {
          ff_opus_rc_enc_end(&s->rc[i], avpkt->data + offset,
                             s->frame[i].framebits >> 3);
          offset += s->frame[i].framebits >> 3;
      }
  
      avpkt->size = offset;
  }
  
  /* Used as overlap for the first frame and padding for the last encoded packet */
  static AVFrame *spawn_empty_frame(OpusEncContext *s)
  {
      AVFrame *f = av_frame_alloc();
      if (!f)
          return NULL;
      f->format         = s->avctx->sample_fmt;
      f->nb_samples     = s->avctx->frame_size;
      f->channel_layout = s->avctx->channel_layout;
      if (av_frame_get_buffer(f, 4)) {
          av_frame_free(&f);
          return NULL;
      }
      for (int i = 0; i < s->channels; i++) {
          size_t bps = av_get_bytes_per_sample(f->format);
          memset(f->extended_data[i], 0, bps*f->nb_samples);
      }
      return f;
  }
  
  static int opus_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
                               const AVFrame *frame, int *got_packet_ptr)
  {
      OpusEncContext *s = avctx->priv_data;
      int ret, frame_size, alloc_size = 0;
  
      if (frame) { /* Add new frame to queue */
          if ((ret = ff_af_queue_add(&s->afq, frame)) < 0)
              return ret;
          ff_bufqueue_add(avctx, &s->bufqueue, av_frame_clone(frame));
      } else {
          ff_opus_psy_signal_eof(&s->psyctx);
          if (!s->afq.remaining_samples || !avctx->frame_number)
              return 0; /* We've been flushed and there's nothing left to encode */
      }
  
      /* Run the psychoacoustic system */
      if (ff_opus_psy_process(&s->psyctx, &s->packet))
          return 0;
  
      frame_size = OPUS_BLOCK_SIZE(s->packet.framesize);
  
      if (!frame) {
          /* This can go negative, that's not a problem, we only pad if positive */
          int pad_empty = s->packet.frames*(frame_size/s->avctx->frame_size) - s->bufqueue.available + 1;
          /* Pad with empty 2.5 ms frames to whatever framesize was decided,
           * this should only happen at the very last flush frame. The frames
           * allocated here will be freed (because they have no other references)
           * after they get used by celt_frame_setup_input() */
          for (int i = 0; i < pad_empty; i++) {
              AVFrame *empty = spawn_empty_frame(s);
              if (!empty)
                  return AVERROR(ENOMEM);
              ff_bufqueue_add(avctx, &s->bufqueue, empty);
          }
      }
  
      for (int i = 0; i < s->packet.frames; i++) {
          celt_encode_frame(s, &s->rc[i], &s->frame[i], i);
          alloc_size += s->frame[i].framebits >> 3;
      }
  
      /* Worst case toc + the frame lengths if needed */
      alloc_size += 2 + s->packet.frames*2;
  
      if ((ret = ff_alloc_packet(avctx, avpkt, alloc_size)) < 0)
          return ret;
  
      /* Assemble packet */
      opus_packet_assembler(s, avpkt);
  
      /* Update the psychoacoustic system */
      ff_opus_psy_postencode_update(&s->psyctx, s->frame, s->rc);
  
      /* Remove samples from queue and skip if needed */
      ff_af_queue_remove(&s->afq, s->packet.frames*frame_size, &avpkt->pts, &avpkt->duration);
      if (s->packet.frames*frame_size > avpkt->duration) {
          uint8_t *side = av_packet_new_side_data(avpkt, AV_PKT_DATA_SKIP_SAMPLES, 10);
          if (!side)
              return AVERROR(ENOMEM);
          AV_WL32(&side[4], s->packet.frames*frame_size - avpkt->duration + 120);
      }
  
      *got_packet_ptr = 1;
  
      return 0;
  }
  
  static av_cold int opus_encode_end(AVCodecContext *avctx)
  {
      OpusEncContext *s = avctx->priv_data;
  
      for (int i = 0; i < CELT_BLOCK_NB; i++)
          ff_mdct15_uninit(&s->mdct[i]);
  
      ff_celt_pvq_uninit(&s->pvq);
      av_freep(&s->dsp);
      av_freep(&s->frame);
      av_freep(&s->rc);
      ff_af_queue_close(&s->afq);
      ff_opus_psy_end(&s->psyctx);
      ff_bufqueue_discard_all(&s->bufqueue);
  
      return 0;
  }
  
  static av_cold int opus_encode_init(AVCodecContext *avctx)
  {
      int ret, max_frames;
      OpusEncContext *s = avctx->priv_data;
  
      s->avctx = avctx;
      s->channels = avctx->channels;
  
      /* Opus allows us to change the framesize on each packet (and each packet may
       * have multiple frames in it) but we can't change the codec's frame size on
       * runtime, so fix it to the lowest possible number of samples and use a queue
       * to accumulate AVFrames until we have enough to encode whatever the encoder
       * decides is the best */
      avctx->frame_size = 120;
      /* Initial padding will change if SILK is ever supported */
      avctx->initial_padding = 120;
  
      if (!avctx->bit_rate) {
          int coupled = ff_opus_default_coupled_streams[s->channels - 1];
          avctx->bit_rate = coupled*(96000) + (s->channels - coupled*2)*(48000);
      } else if (avctx->bit_rate < 6000 || avctx->bit_rate > 255000 * s->channels) {
          int64_t clipped_rate = av_clip(avctx->bit_rate, 6000, 255000 * s->channels);
          av_log(avctx, AV_LOG_ERROR, "Unsupported bitrate %"PRId64" kbps, clipping to %"PRId64" kbps\n",
                 avctx->bit_rate/1000, clipped_rate/1000);
          avctx->bit_rate = clipped_rate;
      }
  
      /* Extradata */
      avctx->extradata_size = 19;
      avctx->extradata = av_malloc(avctx->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
      if (!avctx->extradata)
          return AVERROR(ENOMEM);
      opus_write_extradata(avctx);
  
      ff_af_queue_init(avctx, &s->afq);
  
      if ((ret = ff_celt_pvq_init(&s->pvq, 1)) < 0)
          return ret;
  
      if (!(s->dsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT)))
          return AVERROR(ENOMEM);
  
      /* I have no idea why a base scaling factor of 68 works, could be the twiddles */
      for (int i = 0; i < CELT_BLOCK_NB; i++)
          if ((ret = ff_mdct15_init(&s->mdct[i], 0, i + 3, 68 << (CELT_BLOCK_NB - 1 - i))))
              return AVERROR(ENOMEM);
  
      /* Zero out previous energy (matters for inter first frame) */
      for (int ch = 0; ch < s->channels; ch++)
          memset(s->last_quantized_energy[ch], 0.0f, sizeof(float)*CELT_MAX_BANDS);
  
      /* Allocate an empty frame to use as overlap for the first frame of audio */
      ff_bufqueue_add(avctx, &s->bufqueue, spawn_empty_frame(s));
      if (!ff_bufqueue_peek(&s->bufqueue, 0))
          return AVERROR(ENOMEM);
  
      if ((ret = ff_opus_psy_init(&s->psyctx, s->avctx, &s->bufqueue, &s->options)))
          return ret;
  
      /* Frame structs and range coder buffers */
      max_frames = ceilf(FFMIN(s->options.max_delay_ms, 120.0f)/2.5f);
      s->frame = av_malloc(max_frames*sizeof(CeltFrame));
      if (!s->frame)
          return AVERROR(ENOMEM);
      s->rc = av_malloc(max_frames*sizeof(OpusRangeCoder));
      if (!s->rc)
          return AVERROR(ENOMEM);
  
      for (int i = 0; i < max_frames; i++) {
          s->frame[i].dsp = s->dsp;
          s->frame[i].avctx = s->avctx;
          s->frame[i].seed = 0;
          s->frame[i].pvq = s->pvq;
          s->frame[i].apply_phase_inv = s->options.apply_phase_inv;
          s->frame[i].block[0].emph_coeff = s->frame[i].block[1].emph_coeff = 0.0f;
      }
  
      return 0;
  }
  
  #define OPUSENC_FLAGS AV_OPT_FLAG_ENCODING_PARAM | AV_OPT_FLAG_AUDIO_PARAM
  static const AVOption opusenc_options[] = {
      { "opus_delay", "Maximum delay in milliseconds", offsetof(OpusEncContext, options.max_delay_ms), AV_OPT_TYPE_FLOAT, { .dbl = OPUS_MAX_LOOKAHEAD }, 2.5f, OPUS_MAX_LOOKAHEAD, OPUSENC_FLAGS, "max_delay_ms" },
      { "apply_phase_inv", "Apply intensity stereo phase inversion", offsetof(OpusEncContext, options.apply_phase_inv), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, OPUSENC_FLAGS, "apply_phase_inv" },
      { NULL },
  };
  
  static const AVClass opusenc_class = {
      .class_name = "Opus encoder",
      .item_name  = av_default_item_name,
      .option     = opusenc_options,
      .version    = LIBAVUTIL_VERSION_INT,
  };
  
  static const AVCodecDefault opusenc_defaults[] = {
      { "b", "0" },
      { "compression_level", "10" },
      { NULL },
  };
  
  const AVCodec ff_opus_encoder = {
      .name           = "opus",
      .long_name      = NULL_IF_CONFIG_SMALL("Opus"),
      .type           = AVMEDIA_TYPE_AUDIO,
      .id             = AV_CODEC_ID_OPUS,
      .defaults       = opusenc_defaults,
      .priv_class     = &opusenc_class,
      .priv_data_size = sizeof(OpusEncContext),
      .init           = opus_encode_init,
      .encode2        = opus_encode_frame,
      .close          = opus_encode_end,
      .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
      .capabilities   = AV_CODEC_CAP_EXPERIMENTAL | AV_CODEC_CAP_SMALL_LAST_FRAME | AV_CODEC_CAP_DELAY,
      .supported_samplerates = (const int []){ 48000, 0 },
      .channel_layouts = (const uint64_t []){ AV_CH_LAYOUT_MONO,
                                              AV_CH_LAYOUT_STEREO, 0 },
      .sample_fmts    = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
                                                       AV_SAMPLE_FMT_NONE },
  };
  