avcodec/opus: Rename opus.c->opus_celt.c, opus_celt.c->opusdec_celt.c

Since commit 4fc2531fff112836026aad2bdaf128c9d15a72e3 opus.c
contains only the celt stuff shared between decoder and encoder.
meanwhile, opus_celt.c is decoder-only. So the new names
reflect the actual content better than the current ones.

Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

4 files changed, 977 insertions, 977 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 592d9347f6..37b63cadc2 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -554,11 +554,11 @@ OBJS-$(CONFIG_NELLYMOSER_ENCODER)      += nellymoserenc.o nellymoser.o
 OBJS-$(CONFIG_NOTCHLC_DECODER)         += notchlc.o
 OBJS-$(CONFIG_NUV_DECODER)             += nuv.o rtjpeg.o
 OBJS-$(CONFIG_ON2AVC_DECODER)          += on2avc.o on2avcdata.o
-OBJS-$(CONFIG_OPUS_DECODER)            += opusdec.o opus.o opus_celt.o opus_rc.o \
+OBJS-$(CONFIG_OPUS_DECODER)            += opusdec.o opusdec_celt.o opus_celt.o \
                                           opus_pvq.o opus_silk.o opustab.o vorbis_data.o \
-                                          opusdsp.o opus_parse.o
-OBJS-$(CONFIG_OPUS_ENCODER)            += opusenc.o opus.o opus_rc.o opustab.o opus_pvq.o \
-                                          opusenc_psy.o
+                                          opusdsp.o opus_parse.o opus_rc.o
+OBJS-$(CONFIG_OPUS_ENCODER)            += opusenc.o opusenc_psy.o opus_celt.o \
+                                          opus_pvq.o opus_rc.o opustab.o
 OBJS-$(CONFIG_PAF_AUDIO_DECODER)       += pafaudio.o
 OBJS-$(CONFIG_PAF_VIDEO_DECODER)       += pafvideo.o
 OBJS-$(CONFIG_PAM_DECODER)             += pnmdec.o pnm.o
diff --git a/libavcodec/opus.c b/libavcodec/opus.c
deleted file mode 100644
index a24c38be52..0000000000
--- a/libavcodec/opus.c
+++ /dev/null
@@ -1,484 +0,0 @@
-/*
- * 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
- */
-
-#include <stdint.h>
-
-#include "opus_celt.h"
-#include "opus_pvq.h"
-#include "opustab.h"
-
-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 (!encode)
-        f->alloc_trim = 5;
-    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;
-    }
-}
diff --git a/libavcodec/opus_celt.c b/libavcodec/opus_celt.c
index c2904cc9e0..a24c38be52 100644
--- a/libavcodec/opus_celt.c
+++ b/libavcodec/opus_celt.c
@@ -1,7 +1,6 @@
 /*
  * Copyright (c) 2012 Andrew D'Addesio
  * Copyright (c) 2013-2014 Mozilla Corporation
- * Copyright (c) 2016 Rostislav Pehlivanov <atomnuker@gmail.com>
  *
  * This file is part of FFmpeg.
  *
@@ -20,567 +19,466 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-/**
- * @file
- * Opus CELT decoder
- */
-
-#include <float.h>
+#include <stdint.h>
 
 #include "opus_celt.h"
-#include "opustab.h"
 #include "opus_pvq.h"
+#include "opustab.h"
 
-/* Use the 2D z-transform to apply prediction in both the time domain (alpha)
- * and the frequency domain (beta) */
-static void celt_decode_coarse_energy(CeltFrame *f, OpusRangeCoder *rc)
+void ff_celt_quant_bands(CeltFrame *f, OpusRangeCoder *rc)
 {
-    int i, j;
-    float prev[2] = { 0 };
-    float alpha = ff_celt_alpha_coef[f->size];
-    float beta  = ff_celt_beta_coef[f->size];
-    const uint8_t *model = ff_celt_coarse_energy_dist[f->size][0];
-
-    /* intra frame */
-    if (opus_rc_tell(rc) + 3 <= f->framebits && ff_opus_rc_dec_log(rc, 3)) {
-        alpha = 0.0f;
-        beta  = 1.0f - (4915.0f/32768.0f);
-        model = ff_celt_coarse_energy_dist[f->size][1];
-    }
+    float lowband_scratch[8 * 22];
+    float norm1[2 * 8 * 100];
+    float *norm2 = norm1 + 8 * 100;
 
-    for (i = 0; i < CELT_MAX_BANDS; i++) {
-        for (j = 0; j < f->channels; j++) {
-            CeltBlock *block = &f->block[j];
-            float value;
-            int available;
+    int totalbits = (f->framebits << 3) - f->anticollapse_needed;
 
-            if (i < f->start_band || i >= f->end_band) {
-                block->energy[i] = 0.0;
-                continue;
-            }
+    int update_lowband = 1;
+    int lowband_offset = 0;
 
-            available = f->framebits - opus_rc_tell(rc);
-            if (available >= 15) {
-                /* decode using a Laplace distribution */
-                int k = FFMIN(i, 20) << 1;
-                value = ff_opus_rc_dec_laplace(rc, model[k] << 7, model[k+1] << 6);
-            } else if (available >= 2) {
-                int x = ff_opus_rc_dec_cdf(rc, ff_celt_model_energy_small);
-                value = (x>>1) ^ -(x&1);
-            } else if (available >= 1) {
-                value = -(float)ff_opus_rc_dec_log(rc, 1);
-            } else value = -1;
-
-            block->energy[i] = FFMAX(-9.0f, block->energy[i]) * alpha + prev[j] + value;
-            prev[j] += beta * value;
-        }
-    }
-}
+    int i, j;
 
-static void celt_decode_fine_energy(CeltFrame *f, OpusRangeCoder *rc)
-{
-    int i;
     for (i = f->start_band; i < f->end_band; i++) {
-        int j;
-        if (!f->fine_bits[i])
-            continue;
-
-        for (j = 0; j < f->channels; j++) {
-            CeltBlock *block = &f->block[j];
-            int q2;
-            float offset;
-            q2 = ff_opus_rc_get_raw(rc, f->fine_bits[i]);
-            offset = (q2 + 0.5f) * (1 << (14 - f->fine_bits[i])) / 16384.0f - 0.5f;
-            block->energy[i] += offset;
+        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);
         }
-    }
-}
 
-static void celt_decode_final_energy(CeltFrame *f, OpusRangeCoder *rc)
-{
-    int priority, i, j;
-    int bits_left = f->framebits - opus_rc_tell(rc);
-
-    for (priority = 0; priority < 2; priority++) {
-        for (i = f->start_band; i < f->end_band && bits_left >= f->channels; i++) {
-            if (f->fine_priority[i] != priority || f->fine_bits[i] >= CELT_MAX_FINE_BITS)
-                continue;
-
-            for (j = 0; j < f->channels; j++) {
-                int q2;
-                float offset;
-                q2 = ff_opus_rc_get_raw(rc, 1);
-                offset = (q2 - 0.5f) * (1 << (14 - f->fine_bits[i] - 1)) / 16384.0f;
-                f->block[j].energy[i] += offset;
-                bits_left--;
-            }
-        }
-    }
-}
+        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;
 
-static void celt_decode_tf_changes(CeltFrame *f, OpusRangeCoder *rc)
-{
-    int i, diff = 0, tf_select = 0, tf_changed = 0, tf_select_bit;
-    int consumed, bits = f->transient ? 2 : 4;
+        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;
 
-    consumed = opus_rc_tell(rc);
-    tf_select_bit = (f->size != 0 && consumed+bits+1 <= f->framebits);
+            memcpy(&norm1[band_offset], &norm1[band_offset - count], count * sizeof(float));
 
-    for (i = f->start_band; i < f->end_band; i++) {
-        if (consumed+bits+tf_select_bit <= f->framebits) {
-            diff ^= ff_opus_rc_dec_log(rc, bits);
-            consumed = opus_rc_tell(rc);
-            tf_changed |= diff;
+            if (f->channels == 2)
+                memcpy(&norm2[band_offset], &norm2[band_offset - count], count * sizeof(float));
         }
-        f->tf_change[i] = diff;
-        bits = f->transient ? 4 : 5;
-    }
 
-    if (tf_select_bit && ff_celt_tf_select[f->size][f->transient][0][tf_changed] !=
-                         ff_celt_tf_select[f->size][f->transient][1][tf_changed])
-        tf_select = ff_opus_rc_dec_log(rc, 1);
+        /* 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];
+            }
+        }
 
-    for (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]];
-    }
-}
+        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;
+        }
 
-static void celt_denormalize(CeltFrame *f, CeltBlock *block, float *data)
-{
-    int i, j;
+        norm_loc1 = effective_lowband != -1 ? norm1 + (effective_lowband << f->size) : NULL;
+        norm_loc2 = effective_lowband != -1 ? norm2 + (effective_lowband << f->size) : NULL;
 
-    for (i = f->start_band; i < f->end_band; i++) {
-        float *dst = data + (ff_celt_freq_bands[i] << f->size);
-        float log_norm = block->energy[i] + ff_celt_mean_energy[i];
-        float norm = exp2f(FFMIN(log_norm, 32.0f));
+        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]);
 
-        for (j = 0; j < ff_celt_freq_range[i] << f->size; j++)
-            dst[j] *= norm;
-    }
-}
+            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];
+        }
 
-static void celt_postfilter_apply_transition(CeltBlock *block, float *data)
-{
-    const int T0 = block->pf_period_old;
-    const int T1 = block->pf_period;
-
-    float g00, g01, g02;
-    float g10, g11, g12;
-
-    float x0, x1, x2, x3, x4;
-
-    int i;
-
-    if (block->pf_gains[0]     == 0.0 &&
-        block->pf_gains_old[0] == 0.0)
-        return;
-
-    g00 = block->pf_gains_old[0];
-    g01 = block->pf_gains_old[1];
-    g02 = block->pf_gains_old[2];
-    g10 = block->pf_gains[0];
-    g11 = block->pf_gains[1];
-    g12 = block->pf_gains[2];
-
-    x1 = data[-T1 + 1];
-    x2 = data[-T1];
-    x3 = data[-T1 - 1];
-    x4 = data[-T1 - 2];
-
-    for (i = 0; i < CELT_OVERLAP; i++) {
-        float w = ff_celt_window2[i];
-        x0 = data[i - T1 + 2];
-
-        data[i] +=  (1.0 - w) * g00 * data[i - T0]                          +
-                    (1.0 - w) * g01 * (data[i - T0 - 1] + data[i - T0 + 1]) +
-                    (1.0 - w) * g02 * (data[i - T0 - 2] + data[i - T0 + 2]) +
-                    w         * g10 * x2                                    +
-                    w         * g11 * (x1 + x3)                             +
-                    w         * g12 * (x0 + x4);
-        x4 = x3;
-        x3 = x2;
-        x2 = x1;
-        x1 = x0;
+        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);
     }
 }
 
-static void celt_postfilter(CeltFrame *f, CeltBlock *block)
+#define NORMC(bits) ((bits) << (f->channels - 1) << f->size >> 2)
+
+void ff_celt_bitalloc(CeltFrame *f, OpusRangeCoder *rc, int encode)
 {
-    int len = f->blocksize * f->blocks;
-    const int filter_len = len - 2 * CELT_OVERLAP;
+    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;
+    }
 
-    celt_postfilter_apply_transition(block, block->buf + 1024);
+    /* 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]);
 
-    block->pf_period_old = block->pf_period;
-    memcpy(block->pf_gains_old, block->pf_gains, sizeof(block->pf_gains));
+    /* 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);
+            }
 
-    block->pf_period = block->pf_period_new;
-    memcpy(block->pf_gains, block->pf_gains_new, sizeof(block->pf_gains));
+            if (!is_boost)
+                break;
 
-    if (len > CELT_OVERLAP) {
-        celt_postfilter_apply_transition(block, block->buf + 1024 + CELT_OVERLAP);
+            boost[i]   += quanta;
+            tbits_8ths -= quanta;
 
-        if (block->pf_gains[0] > FLT_EPSILON && filter_len > 0)
-            f->opusdsp.postfilter(block->buf + 1024 + 2 * CELT_OVERLAP,
-                                  block->pf_period, block->pf_gains,
-                                  filter_len);
+            b_dynalloc = 1;
+        }
 
-        block->pf_period_old = block->pf_period;
-        memcpy(block->pf_gains_old, block->pf_gains, sizeof(block->pf_gains));
+        if (boost[i])
+            dynalloc = FFMAX(dynalloc - 1, 2);
     }
 
-    memmove(block->buf, block->buf + len, (1024 + CELT_OVERLAP / 2) * sizeof(float));
-}
-
-static int parse_postfilter(CeltFrame *f, OpusRangeCoder *rc, int consumed)
-{
-    int i;
-
-    memset(f->block[0].pf_gains_new, 0, sizeof(f->block[0].pf_gains_new));
-    memset(f->block[1].pf_gains_new, 0, sizeof(f->block[1].pf_gains_new));
-
-    if (f->start_band == 0 && consumed + 16 <= f->framebits) {
-        int has_postfilter = ff_opus_rc_dec_log(rc, 1);
-        if (has_postfilter) {
-            float gain;
-            int tapset, octave, period;
-
-            octave = ff_opus_rc_dec_uint(rc, 6);
-            period = (16 << octave) + ff_opus_rc_get_raw(rc, 4 + octave) - 1;
-            gain   = 0.09375f * (ff_opus_rc_get_raw(rc, 3) + 1);
-            tapset = (opus_rc_tell(rc) + 2 <= f->framebits) ?
-                     ff_opus_rc_dec_cdf(rc, ff_celt_model_tapset) : 0;
-
-            for (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];
+    /* Allocation trim */
+    if (!encode)
+        f->alloc_trim = 5;
+    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;
         }
-
-        consumed = opus_rc_tell(rc);
     }
 
-    return consumed;
-}
-
-static void process_anticollapse(CeltFrame *f, CeltBlock *block, float *X)
-{
-    int i, j, k;
-
+    /* Trim offsets */
     for (i = f->start_band; i < f->end_band; i++) {
-        int renormalize = 0;
-        float *xptr;
-        float prev[2];
-        float Ediff, r;
-        float thresh, sqrt_1;
-        int depth;
-
-        /* depth in 1/8 bits */
-        depth = (1 + f->pulses[i]) / (ff_celt_freq_range[i] << f->size);
-        thresh = exp2f(-1.0 - 0.125f * depth);
-        sqrt_1 = 1.0f / sqrtf(ff_celt_freq_range[i] << f->size);
-
-        xptr = X + (ff_celt_freq_bands[i] << f->size);
-
-        prev[0] = block->prev_energy[0][i];
-        prev[1] = block->prev_energy[1][i];
-        if (f->channels == 1) {
-            CeltBlock *block1 = &f->block[1];
-
-            prev[0] = FFMAX(prev[0], block1->prev_energy[0][i]);
-            prev[1] = FFMAX(prev[1], block1->prev_energy[1][i]);
-        }
-        Ediff = block->energy[i] - FFMIN(prev[0], prev[1]);
-        Ediff = FFMAX(0, Ediff);
-
-        /* r needs to be multiplied by 2 or 2*sqrt(2) depending on LM because
-        short blocks don't have the same energy as long */
-        r = exp2f(1 - Ediff);
-        if (f->size == 3)
-            r *= M_SQRT2;
-        r = FFMIN(thresh, r) * sqrt_1;
-        for (k = 0; k < 1 << f->size; k++) {
-            /* Detect collapse */
-            if (!(block->collapse_masks[i] & 1 << k)) {
-                /* Fill with noise */
-                for (j = 0; j < ff_celt_freq_range[i]; j++)
-                    xptr[(j << f->size) + k] = (celt_rng(f) & 0x8000) ? r : -r;
-                renormalize = 1;
-            }
-        }
+        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;
 
-        /* We just added some energy, so we need to renormalize */
-        if (renormalize)
-            celt_renormalize_vector(xptr, ff_celt_freq_range[i] << f->size, 1.0f);
-    }
-}
+        /* 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);
 
-int ff_celt_decode_frame(CeltFrame *f, OpusRangeCoder *rc,
-                         float **output, int channels, int frame_size,
-                         int start_band,  int end_band)
-{
-    int i, j, downmix = 0;
-    int consumed;           // bits of entropy consumed thus far for this frame
-    AVTXContext *imdct;
-    av_tx_fn imdct_fn;
-
-    if (channels != 1 && channels != 2) {
-        av_log(f->avctx, AV_LOG_ERROR, "Invalid number of coded channels: %d\n",
-               channels);
-        return AVERROR_INVALIDDATA;
-    }
-    if (start_band < 0 || start_band > end_band || end_band > CELT_MAX_BANDS) {
-        av_log(f->avctx, AV_LOG_ERROR, "Invalid start/end band: %d %d\n",
-               start_band, end_band);
-        return AVERROR_INVALIDDATA;
-    }
+        trim_offset[i] = trim * (band << scale) >> 6;
 
-    f->silence        = 0;
-    f->transient      = 0;
-    f->anticollapse   = 0;
-    f->flushed        = 0;
-    f->channels       = channels;
-    f->start_band     = start_band;
-    f->end_band       = end_band;
-    f->framebits      = rc->rb.bytes * 8;
-
-    f->size = av_log2(frame_size / CELT_SHORT_BLOCKSIZE);
-    if (f->size > CELT_MAX_LOG_BLOCKS ||
-        frame_size != CELT_SHORT_BLOCKSIZE * (1 << f->size)) {
-        av_log(f->avctx, AV_LOG_ERROR, "Invalid CELT frame size: %d\n",
-               frame_size);
-        return AVERROR_INVALIDDATA;
+        if (ff_celt_freq_range[i] << f->size == 1)
+            trim_offset[i] -= f->channels << 3;
     }
 
-    if (!f->output_channels)
-        f->output_channels = channels;
+    /* 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;
+            }
+        }
 
-    for (i = 0; i < f->channels; i++) {
-        memset(f->block[i].coeffs,         0, sizeof(f->block[i].coeffs));
-        memset(f->block[i].collapse_masks, 0, sizeof(f->block[i].collapse_masks));
+        if (total > tbits_8ths)
+            high = center - 1;
+        else
+            low = center + 1;
     }
+    high = low--;
 
-    consumed = opus_rc_tell(rc);
-
-    /* obtain silence flag */
-    if (consumed >= f->framebits)
-        f->silence = 1;
-    else if (consumed == 1)
-        f->silence = ff_opus_rc_dec_log(rc, 15);
-
-
-    if (f->silence) {
-        consumed = f->framebits;
-        rc->total_bits += f->framebits - opus_rc_tell(rc);
+    /* 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);
     }
 
-    /* obtain post-filter options */
-    consumed = parse_postfilter(f, rc, consumed);
-
-    /* obtain transient flag */
-    if (f->size != 0 && consumed+3 <= f->framebits)
-        f->transient = ff_opus_rc_dec_log(rc, 3);
-
-    f->blocks    = f->transient ? 1 << f->size : 1;
-    f->blocksize = frame_size / f->blocks;
-
-    imdct = f->tx[f->transient ? 0 : f->size];
-    imdct_fn = f->tx_fn[f->transient ? 0 : f->size];
-
-    if (channels == 1) {
-        for (i = 0; i < CELT_MAX_BANDS; i++)
-            f->block[0].energy[i] = FFMAX(f->block[0].energy[i], f->block[1].energy[i]);
+    /* 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;
     }
 
-    celt_decode_coarse_energy(f, rc);
-    celt_decode_tf_changes   (f, rc);
-    ff_celt_bitalloc         (f, rc, 0);
-    celt_decode_fine_energy  (f, rc);
-    ff_celt_quant_bands      (f, rc);
-
-    if (f->anticollapse_needed)
-        f->anticollapse = ff_opus_rc_get_raw(rc, 1);
-
-    celt_decode_final_energy(f, rc);
-
-    /* apply anti-collapse processing and denormalization to
-     * each coded channel */
-    for (i = 0; i < f->channels; i++) {
-        CeltBlock *block = &f->block[i];
+    /* 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 (f->anticollapse)
-            process_anticollapse(f, block, f->block[i].coeffs);
+        if (bandbits >= threshold[i] || done)
+            done = 1;
+        else
+            bandbits = (bandbits >= f->channels << 3) ?
+            f->channels << 3 : 0;
 
-        celt_denormalize(f, block, f->block[i].coeffs);
+        bandbits     = FFMIN(bandbits, f->caps[i]);
+        f->pulses[i] = bandbits;
+        total      += bandbits;
     }
 
-    /* stereo -> mono downmix */
-    if (f->output_channels < f->channels) {
-        f->dsp->vector_fmac_scalar(f->block[0].coeffs, f->block[1].coeffs, 1.0, FFALIGN(frame_size, 16));
-        downmix = 1;
-    } else if (f->output_channels > f->channels)
-        memcpy(f->block[1].coeffs, f->block[0].coeffs, frame_size * sizeof(float));
+    /* Band skipping */
+    for (f->coded_bands = f->end_band; ; f->coded_bands--) {
+        int allocation;
+        j = f->coded_bands - 1;
 
-    if (f->silence) {
-        for (i = 0; i < 2; i++) {
-            CeltBlock *block = &f->block[i];
-
-            for (j = 0; j < FF_ARRAY_ELEMS(block->energy); j++)
-                block->energy[j] = CELT_ENERGY_SILENCE;
+        if (j == skip_startband) {
+            /* all remaining bands are not skipped */
+            tbits_8ths += skip_bit;
+            break;
         }
-        memset(f->block[0].coeffs, 0, sizeof(f->block[0].coeffs));
-        memset(f->block[1].coeffs, 0, sizeof(f->block[1].coeffs));
-    }
 
-    /* transform and output for each output channel */
-    for (i = 0; i < f->output_channels; i++) {
-        CeltBlock *block = &f->block[i];
+        /* 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);
+            }
 
-        /* iMDCT and overlap-add */
-        for (j = 0; j < f->blocks; j++) {
-            float *dst  = block->buf + 1024 + j * f->blocksize;
+            if (do_not_skip)
+                break;
 
-            imdct_fn(imdct, dst + CELT_OVERLAP / 2, f->block[i].coeffs + j,
-                     sizeof(float)*f->blocks);
-            f->dsp->vector_fmul_window(dst, dst, dst + CELT_OVERLAP / 2,
-                                       ff_celt_window, CELT_OVERLAP / 2);
+            total      += 1 << 3;
+            allocation -= 1 << 3;
         }
 
-        if (downmix)
-            f->dsp->vector_fmul_scalar(&block->buf[1024], &block->buf[1024], 0.5f, frame_size);
-
-        /* postfilter */
-        celt_postfilter(f, block);
-
-        /* deemphasis */
-        block->emph_coeff = f->opusdsp.deemphasis(output[i],
-                                                  &block->buf[1024 - frame_size],
-                                                  block->emph_coeff, frame_size);
-    }
-
-    if (channels == 1)
-        memcpy(f->block[1].energy, f->block[0].energy, sizeof(f->block[0].energy));
-
-    for (i = 0; i < 2; i++ ) {
-        CeltBlock *block = &f->block[i];
-
-        if (!f->transient) {
-            memcpy(block->prev_energy[1], block->prev_energy[0], sizeof(block->prev_energy[0]));
-            memcpy(block->prev_energy[0], block->energy,         sizeof(block->prev_energy[0]));
-        } else {
-            for (j = 0; j < CELT_MAX_BANDS; j++)
-                block->prev_energy[0][j] = FFMIN(block->prev_energy[0][j], block->energy[j]);
+        /* 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;
         }
 
-        for (j = 0; j < f->start_band; j++) {
-            block->prev_energy[0][j] = CELT_ENERGY_SILENCE;
-            block->energy[j]         = 0.0;
-        }
-        for (j = f->end_band; j < CELT_MAX_BANDS; j++) {
-            block->prev_energy[0][j] = CELT_ENERGY_SILENCE;
-            block->energy[j]         = 0.0;
-        }
+        total += f->pulses[j] = (allocation >= f->channels << 3) ? f->channels << 3 : 0;
     }
 
-    f->seed = rc->range;
-
-    return 0;
-}
-
-void ff_celt_flush(CeltFrame *f)
-{
-    int i, j;
-
-    if (f->flushed)
-        return;
-
-    for (i = 0; i < 2; i++) {
-        CeltBlock *block = &f->block[i];
-
-        for (j = 0; j < CELT_MAX_BANDS; j++)
-            block->prev_energy[0][j] = block->prev_energy[1][j] = CELT_ENERGY_SILENCE;
-
-        memset(block->energy, 0, sizeof(block->energy));
-        memset(block->buf,    0, sizeof(block->buf));
-
-        memset(block->pf_gains,     0, sizeof(block->pf_gains));
-        memset(block->pf_gains_old, 0, sizeof(block->pf_gains_old));
-        memset(block->pf_gains_new, 0, sizeof(block->pf_gains_new));
-
-        /* libopus uses CELT_EMPH_COEFF on init, but 0 is better since there's
-         * a lesser discontinuity when seeking.
-         * The deemphasis functions differ from libopus in that they require
-         * an initial state divided by the coefficient. */
-        block->emph_coeff = 0.0f / CELT_EMPH_COEFF;
+    /* 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);
     }
-    f->seed = 0;
-
-    f->flushed = 1;
-}
-
-void ff_celt_free(CeltFrame **f)
-{
-    CeltFrame *frm = *f;
-    int i;
 
-    if (!frm)
-        return;
-
-    for (i = 0; i < FF_ARRAY_ELEMS(frm->tx); i++)
-        av_tx_uninit(&frm->tx[i]);
-
-    ff_celt_pvq_uninit(&frm->pvq);
-
-    av_freep(&frm->dsp);
-    av_freep(f);
-}
-
-int ff_celt_init(AVCodecContext *avctx, CeltFrame **f, int output_channels,
-                 int apply_phase_inv)
-{
-    CeltFrame *frm;
-    int i, ret;
-
-    if (output_channels != 1 && output_channels != 2) {
-        av_log(avctx, AV_LOG_ERROR, "Invalid number of output channels: %d\n",
-               output_channels);
-        return AVERROR(EINVAL);
+    /* 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;
     }
 
-    frm = av_mallocz(sizeof(*frm));
-    if (!frm)
-        return AVERROR(ENOMEM);
+    /* 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;
+        }
 
-    frm->avctx           = avctx;
-    frm->output_channels = output_channels;
-    frm->apply_phase_inv = apply_phase_inv;
+        /* 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;
 
-    for (i = 0; i < FF_ARRAY_ELEMS(frm->tx); i++) {
-        const float scale = -1.0f/32768;
-        if ((ret = av_tx_init(&frm->tx[i], &frm->tx_fn[i], AV_TX_FLOAT_MDCT, 1, 15 << (i + 3), &scale, 0)) < 0)
-            goto fail;
+            fineextra <<= f->channels + 2;
+            f->fine_priority[i] = (fineextra >= extrabits - prev_extra);
+            extrabits -= fineextra;
+        }
     }
+    f->remaining = extrabits;
 
-    if ((ret = ff_celt_pvq_init(&frm->pvq, 0)) < 0)
-        goto fail;
-
-    frm->dsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
-    if (!frm->dsp) {
-        ret = AVERROR(ENOMEM);
-        goto fail;
+    /* 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;
     }
-
-    ff_opus_dsp_init(&frm->opusdsp);
-    ff_celt_flush(frm);
-
-    *f = frm;
-
-    return 0;
-fail:
-    ff_celt_free(&frm);
-    return ret;
 }
diff --git a/libavcodec/opusdec_celt.c b/libavcodec/opusdec_celt.c
new file mode 100644
index 0000000000..c2904cc9e0
--- /dev/null
+++ b/libavcodec/opusdec_celt.c
@@ -0,0 +1,586 @@
+/*
+ * Copyright (c) 2012 Andrew D'Addesio
+ * Copyright (c) 2013-2014 Mozilla Corporation
+ * Copyright (c) 2016 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
+ */
+
+/**
+ * @file
+ * Opus CELT decoder
+ */
+
+#include <float.h>
+
+#include "opus_celt.h"
+#include "opustab.h"
+#include "opus_pvq.h"
+
+/* Use the 2D z-transform to apply prediction in both the time domain (alpha)
+ * and the frequency domain (beta) */
+static void celt_decode_coarse_energy(CeltFrame *f, OpusRangeCoder *rc)
+{
+    int i, j;
+    float prev[2] = { 0 };
+    float alpha = ff_celt_alpha_coef[f->size];
+    float beta  = ff_celt_beta_coef[f->size];
+    const uint8_t *model = ff_celt_coarse_energy_dist[f->size][0];
+
+    /* intra frame */
+    if (opus_rc_tell(rc) + 3 <= f->framebits && ff_opus_rc_dec_log(rc, 3)) {
+        alpha = 0.0f;
+        beta  = 1.0f - (4915.0f/32768.0f);
+        model = ff_celt_coarse_energy_dist[f->size][1];
+    }
+
+    for (i = 0; i < CELT_MAX_BANDS; i++) {
+        for (j = 0; j < f->channels; j++) {
+            CeltBlock *block = &f->block[j];
+            float value;
+            int available;
+
+            if (i < f->start_band || i >= f->end_band) {
+                block->energy[i] = 0.0;
+                continue;
+            }
+
+            available = f->framebits - opus_rc_tell(rc);
+            if (available >= 15) {
+                /* decode using a Laplace distribution */
+                int k = FFMIN(i, 20) << 1;
+                value = ff_opus_rc_dec_laplace(rc, model[k] << 7, model[k+1] << 6);
+            } else if (available >= 2) {
+                int x = ff_opus_rc_dec_cdf(rc, ff_celt_model_energy_small);
+                value = (x>>1) ^ -(x&1);
+            } else if (available >= 1) {
+                value = -(float)ff_opus_rc_dec_log(rc, 1);
+            } else value = -1;
+
+            block->energy[i] = FFMAX(-9.0f, block->energy[i]) * alpha + prev[j] + value;
+            prev[j] += beta * value;
+        }
+    }
+}
+
+static void celt_decode_fine_energy(CeltFrame *f, OpusRangeCoder *rc)
+{
+    int i;
+    for (i = f->start_band; i < f->end_band; i++) {
+        int j;
+        if (!f->fine_bits[i])
+            continue;
+
+        for (j = 0; j < f->channels; j++) {
+            CeltBlock *block = &f->block[j];
+            int q2;
+            float offset;
+            q2 = ff_opus_rc_get_raw(rc, f->fine_bits[i]);
+            offset = (q2 + 0.5f) * (1 << (14 - f->fine_bits[i])) / 16384.0f - 0.5f;
+            block->energy[i] += offset;
+        }
+    }
+}
+
+static void celt_decode_final_energy(CeltFrame *f, OpusRangeCoder *rc)
+{
+    int priority, i, j;
+    int bits_left = f->framebits - opus_rc_tell(rc);
+
+    for (priority = 0; priority < 2; priority++) {
+        for (i = f->start_band; i < f->end_band && bits_left >= f->channels; i++) {
+            if (f->fine_priority[i] != priority || f->fine_bits[i] >= CELT_MAX_FINE_BITS)
+                continue;
+
+            for (j = 0; j < f->channels; j++) {
+                int q2;
+                float offset;
+                q2 = ff_opus_rc_get_raw(rc, 1);
+                offset = (q2 - 0.5f) * (1 << (14 - f->fine_bits[i] - 1)) / 16384.0f;
+                f->block[j].energy[i] += offset;
+                bits_left--;
+            }
+        }
+    }
+}
+
+static void celt_decode_tf_changes(CeltFrame *f, OpusRangeCoder *rc)
+{
+    int i, diff = 0, tf_select = 0, tf_changed = 0, tf_select_bit;
+    int consumed, bits = f->transient ? 2 : 4;
+
+    consumed = opus_rc_tell(rc);
+    tf_select_bit = (f->size != 0 && consumed+bits+1 <= f->framebits);
+
+    for (i = f->start_band; i < f->end_band; i++) {
+        if (consumed+bits+tf_select_bit <= f->framebits) {
+            diff ^= ff_opus_rc_dec_log(rc, bits);
+            consumed = opus_rc_tell(rc);
+            tf_changed |= diff;
+        }
+        f->tf_change[i] = diff;
+        bits = f->transient ? 4 : 5;
+    }
+
+    if (tf_select_bit && ff_celt_tf_select[f->size][f->transient][0][tf_changed] !=
+                         ff_celt_tf_select[f->size][f->transient][1][tf_changed])
+        tf_select = ff_opus_rc_dec_log(rc, 1);
+
+    for (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_denormalize(CeltFrame *f, CeltBlock *block, float *data)
+{
+    int i, j;
+
+    for (i = f->start_band; i < f->end_band; i++) {
+        float *dst = data + (ff_celt_freq_bands[i] << f->size);
+        float log_norm = block->energy[i] + ff_celt_mean_energy[i];
+        float norm = exp2f(FFMIN(log_norm, 32.0f));
+
+        for (j = 0; j < ff_celt_freq_range[i] << f->size; j++)
+            dst[j] *= norm;
+    }
+}
+
+static void celt_postfilter_apply_transition(CeltBlock *block, float *data)
+{
+    const int T0 = block->pf_period_old;
+    const int T1 = block->pf_period;
+
+    float g00, g01, g02;
+    float g10, g11, g12;
+
+    float x0, x1, x2, x3, x4;
+
+    int i;
+
+    if (block->pf_gains[0]     == 0.0 &&
+        block->pf_gains_old[0] == 0.0)
+        return;
+
+    g00 = block->pf_gains_old[0];
+    g01 = block->pf_gains_old[1];
+    g02 = block->pf_gains_old[2];
+    g10 = block->pf_gains[0];
+    g11 = block->pf_gains[1];
+    g12 = block->pf_gains[2];
+
+    x1 = data[-T1 + 1];
+    x2 = data[-T1];
+    x3 = data[-T1 - 1];
+    x4 = data[-T1 - 2];
+
+    for (i = 0; i < CELT_OVERLAP; i++) {
+        float w = ff_celt_window2[i];
+        x0 = data[i - T1 + 2];
+
+        data[i] +=  (1.0 - w) * g00 * data[i - T0]                          +
+                    (1.0 - w) * g01 * (data[i - T0 - 1] + data[i - T0 + 1]) +
+                    (1.0 - w) * g02 * (data[i - T0 - 2] + data[i - T0 + 2]) +
+                    w         * g10 * x2                                    +
+                    w         * g11 * (x1 + x3)                             +
+                    w         * g12 * (x0 + x4);
+        x4 = x3;
+        x3 = x2;
+        x2 = x1;
+        x1 = x0;
+    }
+}
+
+static void celt_postfilter(CeltFrame *f, CeltBlock *block)
+{
+    int len = f->blocksize * f->blocks;
+    const int filter_len = len - 2 * CELT_OVERLAP;
+
+    celt_postfilter_apply_transition(block, block->buf + 1024);
+
+    block->pf_period_old = block->pf_period;
+    memcpy(block->pf_gains_old, block->pf_gains, sizeof(block->pf_gains));
+
+    block->pf_period = block->pf_period_new;
+    memcpy(block->pf_gains, block->pf_gains_new, sizeof(block->pf_gains));
+
+    if (len > CELT_OVERLAP) {
+        celt_postfilter_apply_transition(block, block->buf + 1024 + CELT_OVERLAP);
+
+        if (block->pf_gains[0] > FLT_EPSILON && filter_len > 0)
+            f->opusdsp.postfilter(block->buf + 1024 + 2 * CELT_OVERLAP,
+                                  block->pf_period, block->pf_gains,
+                                  filter_len);
+
+        block->pf_period_old = block->pf_period;
+        memcpy(block->pf_gains_old, block->pf_gains, sizeof(block->pf_gains));
+    }
+
+    memmove(block->buf, block->buf + len, (1024 + CELT_OVERLAP / 2) * sizeof(float));
+}
+
+static int parse_postfilter(CeltFrame *f, OpusRangeCoder *rc, int consumed)
+{
+    int i;
+
+    memset(f->block[0].pf_gains_new, 0, sizeof(f->block[0].pf_gains_new));
+    memset(f->block[1].pf_gains_new, 0, sizeof(f->block[1].pf_gains_new));
+
+    if (f->start_band == 0 && consumed + 16 <= f->framebits) {
+        int has_postfilter = ff_opus_rc_dec_log(rc, 1);
+        if (has_postfilter) {
+            float gain;
+            int tapset, octave, period;
+
+            octave = ff_opus_rc_dec_uint(rc, 6);
+            period = (16 << octave) + ff_opus_rc_get_raw(rc, 4 + octave) - 1;
+            gain   = 0.09375f * (ff_opus_rc_get_raw(rc, 3) + 1);
+            tapset = (opus_rc_tell(rc) + 2 <= f->framebits) ?
+                     ff_opus_rc_dec_cdf(rc, ff_celt_model_tapset) : 0;
+
+            for (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];
+            }
+        }
+
+        consumed = opus_rc_tell(rc);
+    }
+
+    return consumed;
+}
+
+static void process_anticollapse(CeltFrame *f, CeltBlock *block, float *X)
+{
+    int i, j, k;
+
+    for (i = f->start_band; i < f->end_band; i++) {
+        int renormalize = 0;
+        float *xptr;
+        float prev[2];
+        float Ediff, r;
+        float thresh, sqrt_1;
+        int depth;
+
+        /* depth in 1/8 bits */
+        depth = (1 + f->pulses[i]) / (ff_celt_freq_range[i] << f->size);
+        thresh = exp2f(-1.0 - 0.125f * depth);
+        sqrt_1 = 1.0f / sqrtf(ff_celt_freq_range[i] << f->size);
+
+        xptr = X + (ff_celt_freq_bands[i] << f->size);
+
+        prev[0] = block->prev_energy[0][i];
+        prev[1] = block->prev_energy[1][i];
+        if (f->channels == 1) {
+            CeltBlock *block1 = &f->block[1];
+
+            prev[0] = FFMAX(prev[0], block1->prev_energy[0][i]);
+            prev[1] = FFMAX(prev[1], block1->prev_energy[1][i]);
+        }
+        Ediff = block->energy[i] - FFMIN(prev[0], prev[1]);
+        Ediff = FFMAX(0, Ediff);
+
+        /* r needs to be multiplied by 2 or 2*sqrt(2) depending on LM because
+        short blocks don't have the same energy as long */
+        r = exp2f(1 - Ediff);
+        if (f->size == 3)
+            r *= M_SQRT2;
+        r = FFMIN(thresh, r) * sqrt_1;
+        for (k = 0; k < 1 << f->size; k++) {
+            /* Detect collapse */
+            if (!(block->collapse_masks[i] & 1 << k)) {
+                /* Fill with noise */
+                for (j = 0; j < ff_celt_freq_range[i]; j++)
+                    xptr[(j << f->size) + k] = (celt_rng(f) & 0x8000) ? r : -r;
+                renormalize = 1;
+            }
+        }
+
+        /* We just added some energy, so we need to renormalize */
+        if (renormalize)
+            celt_renormalize_vector(xptr, ff_celt_freq_range[i] << f->size, 1.0f);
+    }
+}
+
+int ff_celt_decode_frame(CeltFrame *f, OpusRangeCoder *rc,
+                         float **output, int channels, int frame_size,
+                         int start_band,  int end_band)
+{
+    int i, j, downmix = 0;
+    int consumed;           // bits of entropy consumed thus far for this frame
+    AVTXContext *imdct;
+    av_tx_fn imdct_fn;
+
+    if (channels != 1 && channels != 2) {
+        av_log(f->avctx, AV_LOG_ERROR, "Invalid number of coded channels: %d\n",
+               channels);
+        return AVERROR_INVALIDDATA;
+    }
+    if (start_band < 0 || start_band > end_band || end_band > CELT_MAX_BANDS) {
+        av_log(f->avctx, AV_LOG_ERROR, "Invalid start/end band: %d %d\n",
+               start_band, end_band);
+        return AVERROR_INVALIDDATA;
+    }
+
+    f->silence        = 0;
+    f->transient      = 0;
+    f->anticollapse   = 0;
+    f->flushed        = 0;
+    f->channels       = channels;
+    f->start_band     = start_band;
+    f->end_band       = end_band;
+    f->framebits      = rc->rb.bytes * 8;
+
+    f->size = av_log2(frame_size / CELT_SHORT_BLOCKSIZE);
+    if (f->size > CELT_MAX_LOG_BLOCKS ||
+        frame_size != CELT_SHORT_BLOCKSIZE * (1 << f->size)) {
+        av_log(f->avctx, AV_LOG_ERROR, "Invalid CELT frame size: %d\n",
+               frame_size);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (!f->output_channels)
+        f->output_channels = channels;
+
+    for (i = 0; i < f->channels; i++) {
+        memset(f->block[i].coeffs,         0, sizeof(f->block[i].coeffs));
+        memset(f->block[i].collapse_masks, 0, sizeof(f->block[i].collapse_masks));
+    }
+
+    consumed = opus_rc_tell(rc);
+
+    /* obtain silence flag */
+    if (consumed >= f->framebits)
+        f->silence = 1;
+    else if (consumed == 1)
+        f->silence = ff_opus_rc_dec_log(rc, 15);
+
+
+    if (f->silence) {
+        consumed = f->framebits;
+        rc->total_bits += f->framebits - opus_rc_tell(rc);
+    }
+
+    /* obtain post-filter options */
+    consumed = parse_postfilter(f, rc, consumed);
+
+    /* obtain transient flag */
+    if (f->size != 0 && consumed+3 <= f->framebits)
+        f->transient = ff_opus_rc_dec_log(rc, 3);
+
+    f->blocks    = f->transient ? 1 << f->size : 1;
+    f->blocksize = frame_size / f->blocks;
+
+    imdct = f->tx[f->transient ? 0 : f->size];
+    imdct_fn = f->tx_fn[f->transient ? 0 : f->size];
+
+    if (channels == 1) {
+        for (i = 0; i < CELT_MAX_BANDS; i++)
+            f->block[0].energy[i] = FFMAX(f->block[0].energy[i], f->block[1].energy[i]);
+    }
+
+    celt_decode_coarse_energy(f, rc);
+    celt_decode_tf_changes   (f, rc);
+    ff_celt_bitalloc         (f, rc, 0);
+    celt_decode_fine_energy  (f, rc);
+    ff_celt_quant_bands      (f, rc);
+
+    if (f->anticollapse_needed)
+        f->anticollapse = ff_opus_rc_get_raw(rc, 1);
+
+    celt_decode_final_energy(f, rc);
+
+    /* apply anti-collapse processing and denormalization to
+     * each coded channel */
+    for (i = 0; i < f->channels; i++) {
+        CeltBlock *block = &f->block[i];
+
+        if (f->anticollapse)
+            process_anticollapse(f, block, f->block[i].coeffs);
+
+        celt_denormalize(f, block, f->block[i].coeffs);
+    }
+
+    /* stereo -> mono downmix */
+    if (f->output_channels < f->channels) {
+        f->dsp->vector_fmac_scalar(f->block[0].coeffs, f->block[1].coeffs, 1.0, FFALIGN(frame_size, 16));
+        downmix = 1;
+    } else if (f->output_channels > f->channels)
+        memcpy(f->block[1].coeffs, f->block[0].coeffs, frame_size * sizeof(float));
+
+    if (f->silence) {
+        for (i = 0; i < 2; i++) {
+            CeltBlock *block = &f->block[i];
+
+            for (j = 0; j < FF_ARRAY_ELEMS(block->energy); j++)
+                block->energy[j] = CELT_ENERGY_SILENCE;
+        }
+        memset(f->block[0].coeffs, 0, sizeof(f->block[0].coeffs));
+        memset(f->block[1].coeffs, 0, sizeof(f->block[1].coeffs));
+    }
+
+    /* transform and output for each output channel */
+    for (i = 0; i < f->output_channels; i++) {
+        CeltBlock *block = &f->block[i];
+
+        /* iMDCT and overlap-add */
+        for (j = 0; j < f->blocks; j++) {
+            float *dst  = block->buf + 1024 + j * f->blocksize;
+
+            imdct_fn(imdct, dst + CELT_OVERLAP / 2, f->block[i].coeffs + j,
+                     sizeof(float)*f->blocks);
+            f->dsp->vector_fmul_window(dst, dst, dst + CELT_OVERLAP / 2,
+                                       ff_celt_window, CELT_OVERLAP / 2);
+        }
+
+        if (downmix)
+            f->dsp->vector_fmul_scalar(&block->buf[1024], &block->buf[1024], 0.5f, frame_size);
+
+        /* postfilter */
+        celt_postfilter(f, block);
+
+        /* deemphasis */
+        block->emph_coeff = f->opusdsp.deemphasis(output[i],
+                                                  &block->buf[1024 - frame_size],
+                                                  block->emph_coeff, frame_size);
+    }
+
+    if (channels == 1)
+        memcpy(f->block[1].energy, f->block[0].energy, sizeof(f->block[0].energy));
+
+    for (i = 0; i < 2; i++ ) {
+        CeltBlock *block = &f->block[i];
+
+        if (!f->transient) {
+            memcpy(block->prev_energy[1], block->prev_energy[0], sizeof(block->prev_energy[0]));
+            memcpy(block->prev_energy[0], block->energy,         sizeof(block->prev_energy[0]));
+        } else {
+            for (j = 0; j < CELT_MAX_BANDS; j++)
+                block->prev_energy[0][j] = FFMIN(block->prev_energy[0][j], block->energy[j]);
+        }
+
+        for (j = 0; j < f->start_band; j++) {
+            block->prev_energy[0][j] = CELT_ENERGY_SILENCE;
+            block->energy[j]         = 0.0;
+        }
+        for (j = f->end_band; j < CELT_MAX_BANDS; j++) {
+            block->prev_energy[0][j] = CELT_ENERGY_SILENCE;
+            block->energy[j]         = 0.0;
+        }
+    }
+
+    f->seed = rc->range;
+
+    return 0;
+}
+
+void ff_celt_flush(CeltFrame *f)
+{
+    int i, j;
+
+    if (f->flushed)
+        return;
+
+    for (i = 0; i < 2; i++) {
+        CeltBlock *block = &f->block[i];
+
+        for (j = 0; j < CELT_MAX_BANDS; j++)
+            block->prev_energy[0][j] = block->prev_energy[1][j] = CELT_ENERGY_SILENCE;
+
+        memset(block->energy, 0, sizeof(block->energy));
+        memset(block->buf,    0, sizeof(block->buf));
+
+        memset(block->pf_gains,     0, sizeof(block->pf_gains));
+        memset(block->pf_gains_old, 0, sizeof(block->pf_gains_old));
+        memset(block->pf_gains_new, 0, sizeof(block->pf_gains_new));
+
+        /* libopus uses CELT_EMPH_COEFF on init, but 0 is better since there's
+         * a lesser discontinuity when seeking.
+         * The deemphasis functions differ from libopus in that they require
+         * an initial state divided by the coefficient. */
+        block->emph_coeff = 0.0f / CELT_EMPH_COEFF;
+    }
+    f->seed = 0;
+
+    f->flushed = 1;
+}
+
+void ff_celt_free(CeltFrame **f)
+{
+    CeltFrame *frm = *f;
+    int i;
+
+    if (!frm)
+        return;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(frm->tx); i++)
+        av_tx_uninit(&frm->tx[i]);
+
+    ff_celt_pvq_uninit(&frm->pvq);
+
+    av_freep(&frm->dsp);
+    av_freep(f);
+}
+
+int ff_celt_init(AVCodecContext *avctx, CeltFrame **f, int output_channels,
+                 int apply_phase_inv)
+{
+    CeltFrame *frm;
+    int i, ret;
+
+    if (output_channels != 1 && output_channels != 2) {
+        av_log(avctx, AV_LOG_ERROR, "Invalid number of output channels: %d\n",
+               output_channels);
+        return AVERROR(EINVAL);
+    }
+
+    frm = av_mallocz(sizeof(*frm));
+    if (!frm)
+        return AVERROR(ENOMEM);
+
+    frm->avctx           = avctx;
+    frm->output_channels = output_channels;
+    frm->apply_phase_inv = apply_phase_inv;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(frm->tx); i++) {
+        const float scale = -1.0f/32768;
+        if ((ret = av_tx_init(&frm->tx[i], &frm->tx_fn[i], AV_TX_FLOAT_MDCT, 1, 15 << (i + 3), &scale, 0)) < 0)
+            goto fail;
+    }
+
+    if ((ret = ff_celt_pvq_init(&frm->pvq, 0)) < 0)
+        goto fail;
+
+    frm->dsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
+    if (!frm->dsp) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+
+    ff_opus_dsp_init(&frm->opusdsp);
+    ff_celt_flush(frm);
+
+    *f = frm;
+
+    return 0;
+fail:
+    ff_celt_free(&frm);
+    return ret;
+}