/*
  * Copyright (c) 2012 Andrew D'Addesio
  * Copyright (c) 2013-2014 Mozilla Corporation
  *

  * 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
  */
 
 /**
  * @file
  * Opus decoder/parser shared code
  */
 
 #include <stdint.h>
 
 #include "libavutil/error.h"

 #include "libavutil/ffmath.h"

 #include "opus_celt.h"
 #include "opustab.h"

 #include "vorbis.h"
 
 static const uint16_t opus_frame_duration[32] = {
     480, 960, 1920, 2880,
     480, 960, 1920, 2880,
     480, 960, 1920, 2880,
     480, 960,
     480, 960,
     120, 240,  480,  960,
     120, 240,  480,  960,
     120, 240,  480,  960,
     120, 240,  480,  960,
 };
 
 /**
  * Read a 1- or 2-byte frame length
  */
 static inline int xiph_lacing_16bit(const uint8_t **ptr, const uint8_t *end)
 {
     int val;
 
     if (*ptr >= end)
         return AVERROR_INVALIDDATA;
     val = *(*ptr)++;
     if (val >= 252) {
         if (*ptr >= end)
             return AVERROR_INVALIDDATA;
         val += 4 * *(*ptr)++;
     }
     return val;
 }
 
 /**
  * Read a multi-byte length (used for code 3 packet padding size)
  */
 static inline int xiph_lacing_full(const uint8_t **ptr, const uint8_t *end)
 {
     int val = 0;
     int next;
 
     while (1) {
         if (*ptr >= end || val > INT_MAX - 254)
             return AVERROR_INVALIDDATA;
         next = *(*ptr)++;
         val += next;
         if (next < 255)
             break;
         else
             val--;
     }
     return val;
 }
 
 /**
  * Parse Opus packet info from raw packet data
  */
 int ff_opus_parse_packet(OpusPacket *pkt, const uint8_t *buf, int buf_size,
                          int self_delimiting)
 {
     const uint8_t *ptr = buf;
     const uint8_t *end = buf + buf_size;
     int padding = 0;
     int frame_bytes, i;
 
     if (buf_size < 1)
         goto fail;
 
     /* TOC byte */
     i = *ptr++;
     pkt->code   = (i     ) & 0x3;
     pkt->stereo = (i >> 2) & 0x1;
     pkt->config = (i >> 3) & 0x1F;
 
     /* code 2 and code 3 packets have at least 1 byte after the TOC */
     if (pkt->code >= 2 && buf_size < 2)
         goto fail;
 
     switch (pkt->code) {
     case 0:
         /* 1 frame */
         pkt->frame_count = 1;
         pkt->vbr         = 0;
 
         if (self_delimiting) {
             int len = xiph_lacing_16bit(&ptr, end);
             if (len < 0 || len > end - ptr)
                 goto fail;
             end      = ptr + len;
             buf_size = end - buf;
         }
 
         frame_bytes = end - ptr;
         if (frame_bytes > MAX_FRAME_SIZE)
             goto fail;
         pkt->frame_offset[0] = ptr - buf;
         pkt->frame_size[0]   = frame_bytes;
         break;
     case 1:
         /* 2 frames, equal size */
         pkt->frame_count = 2;
         pkt->vbr         = 0;
 
         if (self_delimiting) {
             int len = xiph_lacing_16bit(&ptr, end);
             if (len < 0 || 2 * len > end - ptr)
                 goto fail;
             end      = ptr + 2 * len;
             buf_size = end - buf;
         }
 
         frame_bytes = end - ptr;
         if (frame_bytes & 1 || frame_bytes >> 1 > MAX_FRAME_SIZE)
             goto fail;
         pkt->frame_offset[0] = ptr - buf;
         pkt->frame_size[0]   = frame_bytes >> 1;
         pkt->frame_offset[1] = pkt->frame_offset[0] + pkt->frame_size[0];
         pkt->frame_size[1]   = frame_bytes >> 1;
         break;
     case 2:
         /* 2 frames, different sizes */
         pkt->frame_count = 2;
         pkt->vbr         = 1;
 
         /* read 1st frame size */
         frame_bytes = xiph_lacing_16bit(&ptr, end);
         if (frame_bytes < 0)
             goto fail;
 
         if (self_delimiting) {
             int len = xiph_lacing_16bit(&ptr, end);
             if (len < 0 || len + frame_bytes > end - ptr)
                 goto fail;
             end      = ptr + frame_bytes + len;
             buf_size = end - buf;
         }
 
         pkt->frame_offset[0] = ptr - buf;
         pkt->frame_size[0]   = frame_bytes;
 
         /* calculate 2nd frame size */
         frame_bytes = end - ptr - pkt->frame_size[0];
         if (frame_bytes < 0 || frame_bytes > MAX_FRAME_SIZE)
             goto fail;
         pkt->frame_offset[1] = pkt->frame_offset[0] + pkt->frame_size[0];
         pkt->frame_size[1]   = frame_bytes;
         break;
     case 3:
         /* 1 to 48 frames, can be different sizes */
         i = *ptr++;
         pkt->frame_count = (i     ) & 0x3F;
         padding          = (i >> 6) & 0x01;
         pkt->vbr         = (i >> 7) & 0x01;
 
         if (pkt->frame_count == 0 || pkt->frame_count > MAX_FRAMES)
             goto fail;
 
         /* read padding size */
         if (padding) {
             padding = xiph_lacing_full(&ptr, end);
             if (padding < 0)
                 goto fail;
         }
 
         /* read frame sizes */
         if (pkt->vbr) {
             /* for VBR, all frames except the final one have their size coded
                in the bitstream. the last frame size is implicit. */
             int total_bytes = 0;
             for (i = 0; i < pkt->frame_count - 1; i++) {
                 frame_bytes = xiph_lacing_16bit(&ptr, end);
                 if (frame_bytes < 0)
                     goto fail;
                 pkt->frame_size[i] = frame_bytes;
                 total_bytes += frame_bytes;
             }
 
             if (self_delimiting) {
                 int len = xiph_lacing_16bit(&ptr, end);
                 if (len < 0 || len + total_bytes + padding > end - ptr)
                     goto fail;
                 end      = ptr + total_bytes + len + padding;
                 buf_size = end - buf;
             }
 
             frame_bytes = end - ptr - padding;
             if (total_bytes > frame_bytes)
                 goto fail;
             pkt->frame_offset[0] = ptr - buf;
             for (i = 1; i < pkt->frame_count; i++)
                 pkt->frame_offset[i] = pkt->frame_offset[i-1] + pkt->frame_size[i-1];
             pkt->frame_size[pkt->frame_count-1] = frame_bytes - total_bytes;
         } else {
             /* for CBR, the remaining packet bytes are divided evenly between
                the frames */
             if (self_delimiting) {
                 frame_bytes = xiph_lacing_16bit(&ptr, end);
                 if (frame_bytes < 0 || pkt->frame_count * frame_bytes + padding > end - ptr)
                     goto fail;
                 end      = ptr + pkt->frame_count * frame_bytes + padding;
                 buf_size = end - buf;
             } else {
                 frame_bytes = end - ptr - padding;
                 if (frame_bytes % pkt->frame_count ||
                     frame_bytes / pkt->frame_count > MAX_FRAME_SIZE)
                     goto fail;
                 frame_bytes /= pkt->frame_count;
             }
 
             pkt->frame_offset[0] = ptr - buf;
             pkt->frame_size[0]   = frame_bytes;
             for (i = 1; i < pkt->frame_count; i++) {
                 pkt->frame_offset[i] = pkt->frame_offset[i-1] + pkt->frame_size[i-1];
                 pkt->frame_size[i]   = frame_bytes;
             }
         }
     }
 
     pkt->packet_size = buf_size;
     pkt->data_size   = pkt->packet_size - padding;
 
     /* total packet duration cannot be larger than 120ms */
     pkt->frame_duration = opus_frame_duration[pkt->config];
     if (pkt->frame_duration * pkt->frame_count > MAX_PACKET_DUR)
         goto fail;
 
     /* set mode and bandwidth */
     if (pkt->config < 12) {
         pkt->mode = OPUS_MODE_SILK;
         pkt->bandwidth = pkt->config >> 2;
     } else if (pkt->config < 16) {
         pkt->mode = OPUS_MODE_HYBRID;
         pkt->bandwidth = OPUS_BANDWIDTH_SUPERWIDEBAND + (pkt->config >= 14);
     } else {
         pkt->mode = OPUS_MODE_CELT;
         pkt->bandwidth = (pkt->config - 16) >> 2;

         /* skip medium band */

         if (pkt->bandwidth)
             pkt->bandwidth++;
     }
 
     return 0;
 
 fail:
     memset(pkt, 0, sizeof(*pkt));
     return AVERROR_INVALIDDATA;
 }
 
 static int channel_reorder_vorbis(int nb_channels, int channel_idx)
 {
     return ff_vorbis_channel_layout_offsets[nb_channels - 1][channel_idx];
 }
 
 static int channel_reorder_unknown(int nb_channels, int channel_idx)
 {
     return channel_idx;
 }
 
 av_cold int ff_opus_parse_extradata(AVCodecContext *avctx,
                                     OpusContext *s)
 {
     static const uint8_t default_channel_map[2] = { 0, 1 };
 
     int (*channel_reorder)(int, int) = channel_reorder_unknown;
 
     const uint8_t *extradata, *channel_map;
     int extradata_size;
     int version, channels, map_type, streams, stereo_streams, i, j;
     uint64_t layout;
 
     if (!avctx->extradata) {
         if (avctx->channels > 2) {
             av_log(avctx, AV_LOG_ERROR,
                    "Multichannel configuration without extradata.\n");
             return AVERROR(EINVAL);
         }

         extradata      = opus_default_extradata;
         extradata_size = sizeof(opus_default_extradata);

     } else {
         extradata = avctx->extradata;
         extradata_size = avctx->extradata_size;
     }
 
     if (extradata_size < 19) {
         av_log(avctx, AV_LOG_ERROR, "Invalid extradata size: %d\n",
                extradata_size);
         return AVERROR_INVALIDDATA;
     }
 
     version = extradata[8];
     if (version > 15) {
         avpriv_request_sample(avctx, "Extradata version %d", version);
         return AVERROR_PATCHWELCOME;
     }
 
     avctx->delay = AV_RL16(extradata + 10);
 

     channels = avctx->extradata ? extradata[9] : (avctx->channels == 1) ? 1 : 2;

     if (!channels) {

         av_log(avctx, AV_LOG_ERROR, "Zero channel count specified in the extradata\n");

         return AVERROR_INVALIDDATA;
     }
 
     s->gain_i = AV_RL16(extradata + 16);
     if (s->gain_i)

         s->gain = ff_exp10(s->gain_i / (20.0 * 256));

 
     map_type = extradata[18];
     if (!map_type) {
         if (channels > 2) {
             av_log(avctx, AV_LOG_ERROR,
                    "Channel mapping 0 is only specified for up to 2 channels\n");
             return AVERROR_INVALIDDATA;
         }
         layout         = (channels == 1) ? AV_CH_LAYOUT_MONO : AV_CH_LAYOUT_STEREO;
         streams        = 1;
         stereo_streams = channels - 1;
         channel_map    = default_channel_map;

     } else if (map_type == 1 || map_type == 2 || map_type == 255) {

         if (extradata_size < 21 + channels) {
             av_log(avctx, AV_LOG_ERROR, "Invalid extradata size: %d\n",
                    extradata_size);
             return AVERROR_INVALIDDATA;
         }
 
         streams        = extradata[19];
         stereo_streams = extradata[20];
         if (!streams || stereo_streams > streams ||
             streams + stereo_streams > 255) {
             av_log(avctx, AV_LOG_ERROR,
                    "Invalid stream/stereo stream count: %d/%d\n", streams, stereo_streams);
             return AVERROR_INVALIDDATA;
         }
 
         if (map_type == 1) {
             if (channels > 8) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Channel mapping 1 is only specified for up to 8 channels\n");
                 return AVERROR_INVALIDDATA;
             }
             layout = ff_vorbis_channel_layouts[channels - 1];
             channel_reorder = channel_reorder_vorbis;

         } else if (map_type == 2) {
             int ambisonic_order = ff_sqrt(channels) - 1;

             if (channels != ((ambisonic_order + 1) * (ambisonic_order + 1)) &&
                 channels != ((ambisonic_order + 1) * (ambisonic_order + 1) + 2)) {

                 av_log(avctx, AV_LOG_ERROR,
                        "Channel mapping 2 is only specified for channel counts"

                        " which can be written as (n + 1)^2 or (n + 1)^2 + 2"
                        " for nonnegative integer n\n");

                 return AVERROR_INVALIDDATA;
             }

             if (channels > 227) {
                 av_log(avctx, AV_LOG_ERROR, "Too many channels\n");
                 return AVERROR_INVALIDDATA;
             }

             layout = 0;

         } else
             layout = 0;
 
         channel_map = extradata + 21;
     } else {
         avpriv_request_sample(avctx, "Mapping type %d", map_type);
         return AVERROR_PATCHWELCOME;
     }
 
     s->channel_maps = av_mallocz_array(channels, sizeof(*s->channel_maps));
     if (!s->channel_maps)
         return AVERROR(ENOMEM);
 
     for (i = 0; i < channels; i++) {
         ChannelMap *map = &s->channel_maps[i];
         uint8_t     idx = channel_map[channel_reorder(channels, i)];
 
         if (idx == 255) {
             map->silence = 1;
             continue;
         } else if (idx >= streams + stereo_streams) {
             av_log(avctx, AV_LOG_ERROR,
                    "Invalid channel map for output channel %d: %d\n", i, idx);

             av_freep(&s->channel_maps);

             return AVERROR_INVALIDDATA;
         }
 

         /* check that we did not see this index yet */

         map->copy = 0;
         for (j = 0; j < i; j++)
             if (channel_map[channel_reorder(channels, j)] == idx) {
                 map->copy     = 1;
                 map->copy_idx = j;
                 break;
             }
 
         if (idx < 2 * stereo_streams) {
             map->stream_idx  = idx / 2;
             map->channel_idx = idx & 1;
         } else {
             map->stream_idx  = idx - stereo_streams;
             map->channel_idx = 0;
         }
     }
 
     avctx->channels       = channels;
     avctx->channel_layout = layout;
     s->nb_streams         = streams;
     s->nb_stereo_streams  = stereo_streams;
 
     return 0;
 }

 
 void ff_celt_quant_bands(CeltFrame *f, OpusRangeCoder *rc)
 {
     float lowband_scratch[8 * 22];
     float norm1[2 * 8 * 100];
     float *norm2 = norm1 + 8 * 100;
 
     int totalbits = (f->framebits << 3) - f->anticollapse_needed;
 
     int update_lowband = 1;
     int lowband_offset = 0;
 
     int i, j;
 
     for (i = f->start_band; i < f->end_band; i++) {
         uint32_t cm[2] = { (1 << f->blocks) - 1, (1 << f->blocks) - 1 };
         int band_offset = ff_celt_freq_bands[i] << f->size;
         int band_size   = ff_celt_freq_range[i] << f->size;
         float *X = f->block[0].coeffs + band_offset;
         float *Y = (f->channels == 2) ? f->block[1].coeffs + band_offset : NULL;
         float *norm_loc1, *norm_loc2;
 
         int consumed = opus_rc_tell_frac(rc);
         int effective_lowband = -1;
         int b = 0;
 
         /* Compute how many bits we want to allocate to this band */
         if (i != f->start_band)
             f->remaining -= consumed;
         f->remaining2 = totalbits - consumed - 1;
         if (i <= f->coded_bands - 1) {
             int curr_balance = f->remaining / FFMIN(3, f->coded_bands-i);
             b = av_clip_uintp2(FFMIN(f->remaining2 + 1, f->pulses[i] + curr_balance), 14);
         }
 
         if ((ff_celt_freq_bands[i] - ff_celt_freq_range[i] >= ff_celt_freq_bands[f->start_band] ||
             i == f->start_band + 1) && (update_lowband || lowband_offset == 0))
             lowband_offset = i;
 
         if (i == f->start_band + 1) {
             /* Special Hybrid Folding (RFC 8251 section 9). Copy the first band into
             the second to ensure the second band never has to use the LCG. */

             int count = (ff_celt_freq_range[i] - ff_celt_freq_range[i-1]) << f->size;

             memcpy(&norm1[band_offset], &norm1[band_offset - count], count * sizeof(float));

 
             if (f->channels == 2)

                 memcpy(&norm2[band_offset], &norm2[band_offset - count], count * sizeof(float));

         }
 
         /* Get a conservative estimate of the collapse_mask's for the bands we're
            going to be folding from. */
         if (lowband_offset != 0 && (f->spread != CELT_SPREAD_AGGRESSIVE ||
                                     f->blocks > 1 || f->tf_change[i] < 0)) {
             int foldstart, foldend;
 
             /* This ensures we never repeat spectral content within one band */
             effective_lowband = FFMAX(ff_celt_freq_bands[f->start_band],
                                       ff_celt_freq_bands[lowband_offset] - ff_celt_freq_range[i]);
             foldstart = lowband_offset;
             while (ff_celt_freq_bands[--foldstart] > effective_lowband);
             foldend = lowband_offset - 1;
             while (++foldend < i && ff_celt_freq_bands[foldend] < effective_lowband + ff_celt_freq_range[i]);
 
             cm[0] = cm[1] = 0;
             for (j = foldstart; j < foldend; j++) {
                 cm[0] |= f->block[0].collapse_masks[j];
                 cm[1] |= f->block[f->channels - 1].collapse_masks[j];
             }
         }
 
         if (f->dual_stereo && i == f->intensity_stereo) {
             /* Switch off dual stereo to do intensity */
             f->dual_stereo = 0;
             for (j = ff_celt_freq_bands[f->start_band] << f->size; j < band_offset; j++)
                 norm1[j] = (norm1[j] + norm2[j]) / 2;
         }
 
         norm_loc1 = effective_lowband != -1 ? norm1 + (effective_lowband << f->size) : NULL;
         norm_loc2 = effective_lowband != -1 ? norm2 + (effective_lowband << f->size) : NULL;
 
         if (f->dual_stereo) {
             cm[0] = f->pvq->quant_band(f->pvq, f, rc, i, X, NULL, band_size, b >> 1,
                                        f->blocks, norm_loc1, f->size,
                                        norm1 + band_offset, 0, 1.0f,
                                        lowband_scratch, cm[0]);
 
             cm[1] = f->pvq->quant_band(f->pvq, f, rc, i, Y, NULL, band_size, b >> 1,
                                        f->blocks, norm_loc2, f->size,
                                        norm2 + band_offset, 0, 1.0f,
                                        lowband_scratch, cm[1]);
         } else {
             cm[0] = f->pvq->quant_band(f->pvq, f, rc, i, X,    Y, band_size, b >> 0,
                                        f->blocks, norm_loc1, f->size,
                                        norm1 + band_offset, 0, 1.0f,
                                        lowband_scratch, cm[0] | cm[1]);
             cm[1] = cm[0];
         }
 
         f->block[0].collapse_masks[i]               = (uint8_t)cm[0];
         f->block[f->channels - 1].collapse_masks[i] = (uint8_t)cm[1];
         f->remaining += f->pulses[i] + consumed;
 
         /* Update the folding position only as long as we have 1 bit/sample depth */
         update_lowband = (b > band_size << 3);
     }
 }

 
 #define NORMC(bits) ((bits) << (f->channels - 1) << f->size >> 2)
 
 void ff_celt_bitalloc(CeltFrame *f, OpusRangeCoder *rc, int encode)
 {
     int i, j, low, high, total, done, bandbits, remaining, tbits_8ths;
     int skip_startband      = f->start_band;
     int skip_bit            = 0;
     int intensitystereo_bit = 0;
     int dualstereo_bit      = 0;
     int dynalloc            = 6;
     int extrabits           = 0;
 
     int boost[CELT_MAX_BANDS] = { 0 };
     int trim_offset[CELT_MAX_BANDS];
     int threshold[CELT_MAX_BANDS];
     int bits1[CELT_MAX_BANDS];
     int bits2[CELT_MAX_BANDS];
 
     /* Spread */

     if (opus_rc_tell(rc) + 4 <= f->framebits) {

         if (encode)
             ff_opus_rc_enc_cdf(rc, f->spread, ff_celt_model_spread);
         else
             f->spread = ff_opus_rc_dec_cdf(rc, ff_celt_model_spread);

     } else {

         f->spread = CELT_SPREAD_NORMAL;

     }

 
     /* Initialize static allocation caps */
     for (i = 0; i < CELT_MAX_BANDS; i++)
         f->caps[i] = NORMC((ff_celt_static_caps[f->size][f->channels - 1][i] + 64) * ff_celt_freq_range[i]);
 
     /* Band boosts */
     tbits_8ths = f->framebits << 3;
     for (i = f->start_band; i < f->end_band; i++) {
         int quanta = ff_celt_freq_range[i] << (f->channels - 1) << f->size;
         int b_dynalloc = dynalloc;
         int boost_amount = f->alloc_boost[i];
         quanta = FFMIN(quanta << 3, FFMAX(6 << 3, quanta));
 
         while (opus_rc_tell_frac(rc) + (b_dynalloc << 3) < tbits_8ths && boost[i] < f->caps[i]) {
             int is_boost;
             if (encode) {
                 is_boost = boost_amount--;
                 ff_opus_rc_enc_log(rc, is_boost, b_dynalloc);
             } else {
                 is_boost = ff_opus_rc_dec_log(rc, b_dynalloc);
             }
 
             if (!is_boost)
                 break;
 
             boost[i]   += quanta;
             tbits_8ths -= quanta;
 
             b_dynalloc = 1;
         }
 
         if (boost[i])
             dynalloc = FFMAX(dynalloc - 1, 2);
     }
 
     /* Allocation trim */
     if (opus_rc_tell_frac(rc) + (6 << 3) <= tbits_8ths)
         if (encode)
             ff_opus_rc_enc_cdf(rc, f->alloc_trim, ff_celt_model_alloc_trim);
         else
             f->alloc_trim = ff_opus_rc_dec_cdf(rc, ff_celt_model_alloc_trim);
 
     /* Anti-collapse bit reservation */
     tbits_8ths = (f->framebits << 3) - opus_rc_tell_frac(rc) - 1;
     f->anticollapse_needed = 0;
     if (f->transient && f->size >= 2 && tbits_8ths >= ((f->size + 2) << 3))
         f->anticollapse_needed = 1 << 3;
     tbits_8ths -= f->anticollapse_needed;
 
     /* Band skip bit reservation */
     if (tbits_8ths >= 1 << 3)
         skip_bit = 1 << 3;
     tbits_8ths -= skip_bit;
 
     /* Intensity/dual stereo bit reservation */
     if (f->channels == 2) {
         intensitystereo_bit = ff_celt_log2_frac[f->end_band - f->start_band];
         if (intensitystereo_bit <= tbits_8ths) {
             tbits_8ths -= intensitystereo_bit;
             if (tbits_8ths >= 1 << 3) {
                 dualstereo_bit = 1 << 3;
                 tbits_8ths -= 1 << 3;
             }
         } else {
             intensitystereo_bit = 0;
         }
     }
 
     /* Trim offsets */
     for (i = f->start_band; i < f->end_band; i++) {
         int trim     = f->alloc_trim - 5 - f->size;
         int band     = ff_celt_freq_range[i] * (f->end_band - i - 1);
         int duration = f->size + 3;
         int scale    = duration + f->channels - 1;
 
         /* PVQ minimum allocation threshold, below this value the band is
          * skipped */
         threshold[i] = FFMAX(3 * ff_celt_freq_range[i] << duration >> 4,
                              f->channels << 3);
 
         trim_offset[i] = trim * (band << scale) >> 6;
 
         if (ff_celt_freq_range[i] << f->size == 1)
             trim_offset[i] -= f->channels << 3;
     }
 
     /* Bisection */
     low  = 1;
     high = CELT_VECTORS - 1;
     while (low <= high) {
         int center = (low + high) >> 1;
         done = total = 0;
 
         for (i = f->end_band - 1; i >= f->start_band; i--) {
             bandbits = NORMC(ff_celt_freq_range[i] * ff_celt_static_alloc[center][i]);
 
             if (bandbits)
                 bandbits = FFMAX(bandbits + trim_offset[i], 0);
             bandbits += boost[i];
 
             if (bandbits >= threshold[i] || done) {
                 done = 1;
                 total += FFMIN(bandbits, f->caps[i]);
             } else if (bandbits >= f->channels << 3) {
                 total += f->channels << 3;
             }
         }
 
         if (total > tbits_8ths)
             high = center - 1;
         else
             low = center + 1;
     }
     high = low--;
 
     /* Bisection */
     for (i = f->start_band; i < f->end_band; i++) {
         bits1[i] = NORMC(ff_celt_freq_range[i] * ff_celt_static_alloc[low][i]);
         bits2[i] = high >= CELT_VECTORS ? f->caps[i] :
                    NORMC(ff_celt_freq_range[i] * ff_celt_static_alloc[high][i]);
 
         if (bits1[i])
             bits1[i] = FFMAX(bits1[i] + trim_offset[i], 0);
         if (bits2[i])
             bits2[i] = FFMAX(bits2[i] + trim_offset[i], 0);
 
         if (low)
             bits1[i] += boost[i];
         bits2[i] += boost[i];
 
         if (boost[i])
             skip_startband = i;
         bits2[i] = FFMAX(bits2[i] - bits1[i], 0);
     }
 
     /* Bisection */
     low  = 0;
     high = 1 << CELT_ALLOC_STEPS;
     for (i = 0; i < CELT_ALLOC_STEPS; i++) {
         int center = (low + high) >> 1;
         done = total = 0;
 
         for (j = f->end_band - 1; j >= f->start_band; j--) {
             bandbits = bits1[j] + (center * bits2[j] >> CELT_ALLOC_STEPS);
 
             if (bandbits >= threshold[j] || done) {
                 done = 1;
                 total += FFMIN(bandbits, f->caps[j]);
             } else if (bandbits >= f->channels << 3)
                 total += f->channels << 3;
         }
         if (total > tbits_8ths)
             high = center;
         else
             low = center;
     }
 
     /* Bisection */
     done = total = 0;
     for (i = f->end_band - 1; i >= f->start_band; i--) {
         bandbits = bits1[i] + (low * bits2[i] >> CELT_ALLOC_STEPS);
 
         if (bandbits >= threshold[i] || done)
             done = 1;
         else
             bandbits = (bandbits >= f->channels << 3) ?
             f->channels << 3 : 0;
 
         bandbits     = FFMIN(bandbits, f->caps[i]);
         f->pulses[i] = bandbits;
         total      += bandbits;
     }
 
     /* Band skipping */
     for (f->coded_bands = f->end_band; ; f->coded_bands--) {
         int allocation;
         j = f->coded_bands - 1;
 
         if (j == skip_startband) {
             /* all remaining bands are not skipped */
             tbits_8ths += skip_bit;
             break;
         }
 
         /* determine the number of bits available for coding "do not skip" markers */
         remaining   = tbits_8ths - total;
         bandbits    = remaining / (ff_celt_freq_bands[j+1] - ff_celt_freq_bands[f->start_band]);
         remaining  -= bandbits  * (ff_celt_freq_bands[j+1] - ff_celt_freq_bands[f->start_band]);
         allocation  = f->pulses[j] + bandbits * ff_celt_freq_range[j];
         allocation += FFMAX(remaining - (ff_celt_freq_bands[j] - ff_celt_freq_bands[f->start_band]), 0);
 
         /* a "do not skip" marker is only coded if the allocation is
          * above the chosen threshold */
         if (allocation >= FFMAX(threshold[j], (f->channels + 1) << 3)) {
             int do_not_skip;
             if (encode) {
                 do_not_skip = f->coded_bands <= f->skip_band_floor;
                 ff_opus_rc_enc_log(rc, do_not_skip, 1);
             } else {
                 do_not_skip = ff_opus_rc_dec_log(rc, 1);
             }
 
             if (do_not_skip)
                 break;
 
             total      += 1 << 3;
             allocation -= 1 << 3;
         }
 
         /* the band is skipped, so reclaim its bits */
         total -= f->pulses[j];
         if (intensitystereo_bit) {
             total -= intensitystereo_bit;
             intensitystereo_bit = ff_celt_log2_frac[j - f->start_band];
             total += intensitystereo_bit;
         }
 
         total += f->pulses[j] = (allocation >= f->channels << 3) ? f->channels << 3 : 0;
     }
 
     /* IS start band */
     if (encode) {
         if (intensitystereo_bit) {
             f->intensity_stereo = FFMIN(f->intensity_stereo, f->coded_bands);
             ff_opus_rc_enc_uint(rc, f->intensity_stereo, f->coded_bands + 1 - f->start_band);
         }
     } else {
         f->intensity_stereo = f->dual_stereo = 0;
         if (intensitystereo_bit)
             f->intensity_stereo = f->start_band + ff_opus_rc_dec_uint(rc, f->coded_bands + 1 - f->start_band);
     }
 
     /* DS flag */
     if (f->intensity_stereo <= f->start_band)
         tbits_8ths += dualstereo_bit; /* no intensity stereo means no dual stereo */
     else if (dualstereo_bit)
         if (encode)
             ff_opus_rc_enc_log(rc, f->dual_stereo, 1);
         else
             f->dual_stereo = ff_opus_rc_dec_log(rc, 1);
 
     /* Supply the remaining bits in this frame to lower bands */
     remaining = tbits_8ths - total;
     bandbits  = remaining / (ff_celt_freq_bands[f->coded_bands] - ff_celt_freq_bands[f->start_band]);
     remaining -= bandbits * (ff_celt_freq_bands[f->coded_bands] - ff_celt_freq_bands[f->start_band]);
     for (i = f->start_band; i < f->coded_bands; i++) {
         const int bits = FFMIN(remaining, ff_celt_freq_range[i]);
         f->pulses[i] += bits + bandbits * ff_celt_freq_range[i];
         remaining    -= bits;
     }
 
     /* Finally determine the allocation */
     for (i = f->start_band; i < f->coded_bands; i++) {
         int N = ff_celt_freq_range[i] << f->size;
         int prev_extra = extrabits;
         f->pulses[i] += extrabits;
 
         if (N > 1) {
             int dof;        /* degrees of freedom */
             int temp;       /* dof * channels * log(dof) */
             int fine_bits;
             int max_bits;
             int offset;     /* fine energy quantization offset, i.e.
                              * extra bits assigned over the standard
                              * totalbits/dof */
 
             extrabits = FFMAX(f->pulses[i] - f->caps[i], 0);
             f->pulses[i] -= extrabits;
 
             /* intensity stereo makes use of an extra degree of freedom */
             dof = N * f->channels + (f->channels == 2 && N > 2 && !f->dual_stereo && i < f->intensity_stereo);
             temp = dof * (ff_celt_log_freq_range[i] + (f->size << 3));
             offset = (temp >> 1) - dof * CELT_FINE_OFFSET;
             if (N == 2) /* dof=2 is the only case that doesn't fit the model */
                 offset += dof << 1;
 
             /* grant an additional bias for the first and second pulses */
             if (f->pulses[i] + offset < 2 * (dof << 3))
                 offset += temp >> 2;
             else if (f->pulses[i] + offset < 3 * (dof << 3))
                 offset += temp >> 3;
 
             fine_bits = (f->pulses[i] + offset + (dof << 2)) / (dof << 3);
             max_bits  = FFMIN((f->pulses[i] >> 3) >> (f->channels - 1), CELT_MAX_FINE_BITS);
             max_bits  = FFMAX(max_bits, 0);
             f->fine_bits[i] = av_clip(fine_bits, 0, max_bits);
 
             /* If fine_bits was rounded down or capped,
              * give priority for the final fine energy pass */
             f->fine_priority[i] = (f->fine_bits[i] * (dof << 3) >= f->pulses[i] + offset);
 
             /* the remaining bits are assigned to PVQ */
             f->pulses[i] -= f->fine_bits[i] << (f->channels - 1) << 3;
         } else {
             /* all bits go to fine energy except for the sign bit */
             extrabits = FFMAX(f->pulses[i] - (f->channels << 3), 0);
             f->pulses[i] -= extrabits;
             f->fine_bits[i] = 0;
             f->fine_priority[i] = 1;
         }
 
         /* hand back a limited number of extra fine energy bits to this band */
         if (extrabits > 0) {
             int fineextra = FFMIN(extrabits >> (f->channels + 2),
                                   CELT_MAX_FINE_BITS - f->fine_bits[i]);
             f->fine_bits[i] += fineextra;
 
             fineextra <<= f->channels + 2;
             f->fine_priority[i] = (fineextra >= extrabits - prev_extra);
             extrabits -= fineextra;
         }
     }
     f->remaining = extrabits;
 
     /* skipped bands dedicate all of their bits for fine energy */
     for (; i < f->end_band; i++) {
         f->fine_bits[i]     = f->pulses[i] >> (f->channels - 1) >> 3;
         f->pulses[i]        = 0;
         f->fine_priority[i] = f->fine_bits[i] < 1;
     }
 }