making act segmenter

1 files changed, 1488 insertions, 0 deletions

diff --git a/ffmpeg/libavcodec/ac3dec.c b/ffmpeg/libavcodec/ac3dec.c
new file mode 100644
index 0000000..a70d92a
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+++ b/ffmpeg/libavcodec/ac3dec.c
@@ -0,0 +1,1488 @@
+/*
+ * AC-3 Audio Decoder
+ * This code was developed as part of Google Summer of Code 2006.
+ * E-AC-3 support was added as part of Google Summer of Code 2007.
+ *
+ * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com)
+ * Copyright (c) 2007-2008 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
+ * Copyright (c) 2007 Justin Ruggles <justin.ruggles@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdio.h>
+#include <stddef.h>
+#include <math.h>
+#include <string.h>
+
+#include "libavutil/crc.h"
+#include "libavutil/opt.h"
+#include "internal.h"
+#include "aac_ac3_parser.h"
+#include "ac3_parser.h"
+#include "ac3dec.h"
+#include "ac3dec_data.h"
+#include "kbdwin.h"
+
+/**
+ * table for ungrouping 3 values in 7 bits.
+ * used for exponents and bap=2 mantissas
+ */
+static uint8_t ungroup_3_in_7_bits_tab[128][3];
+
+/** tables for ungrouping mantissas */
+static int b1_mantissas[32][3];
+static int b2_mantissas[128][3];
+static int b3_mantissas[8];
+static int b4_mantissas[128][2];
+static int b5_mantissas[16];
+
+/**
+ * Quantization table: levels for symmetric. bits for asymmetric.
+ * reference: Table 7.18 Mapping of bap to Quantizer
+ */
+static const uint8_t quantization_tab[16] = {
+    0, 3, 5, 7, 11, 15,
+    5, 6, 7, 8, 9, 10, 11, 12, 14, 16
+};
+
+/** dynamic range table. converts codes to scale factors. */
+static float dynamic_range_tab[256];
+
+/** Adjustments in dB gain */
+static const float gain_levels[9] = {
+    LEVEL_PLUS_3DB,
+    LEVEL_PLUS_1POINT5DB,
+    LEVEL_ONE,
+    LEVEL_MINUS_1POINT5DB,
+    LEVEL_MINUS_3DB,
+    LEVEL_MINUS_4POINT5DB,
+    LEVEL_MINUS_6DB,
+    LEVEL_ZERO,
+    LEVEL_MINUS_9DB
+};
+
+/**
+ * Table for default stereo downmixing coefficients
+ * reference: Section 7.8.2 Downmixing Into Two Channels
+ */
+static const uint8_t ac3_default_coeffs[8][5][2] = {
+    { { 2, 7 }, { 7, 2 },                               },
+    { { 4, 4 },                                         },
+    { { 2, 7 }, { 7, 2 },                               },
+    { { 2, 7 }, { 5, 5 }, { 7, 2 },                     },
+    { { 2, 7 }, { 7, 2 }, { 6, 6 },                     },
+    { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 8, 8 },           },
+    { { 2, 7 }, { 7, 2 }, { 6, 7 }, { 7, 6 },           },
+    { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
+};
+
+/**
+ * Symmetrical Dequantization
+ * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
+ *            Tables 7.19 to 7.23
+ */
+static inline int
+symmetric_dequant(int code, int levels)
+{
+    return ((code - (levels >> 1)) << 24) / levels;
+}
+
+/*
+ * Initialize tables at runtime.
+ */
+static av_cold void ac3_tables_init(void)
+{
+    int i;
+
+    /* generate table for ungrouping 3 values in 7 bits
+       reference: Section 7.1.3 Exponent Decoding */
+    for (i = 0; i < 128; i++) {
+        ungroup_3_in_7_bits_tab[i][0] =  i / 25;
+        ungroup_3_in_7_bits_tab[i][1] = (i % 25) / 5;
+        ungroup_3_in_7_bits_tab[i][2] = (i % 25) % 5;
+    }
+
+    /* generate grouped mantissa tables
+       reference: Section 7.3.5 Ungrouping of Mantissas */
+    for (i = 0; i < 32; i++) {
+        /* bap=1 mantissas */
+        b1_mantissas[i][0] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][0], 3);
+        b1_mantissas[i][1] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][1], 3);
+        b1_mantissas[i][2] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][2], 3);
+    }
+    for (i = 0; i < 128; i++) {
+        /* bap=2 mantissas */
+        b2_mantissas[i][0] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][0], 5);
+        b2_mantissas[i][1] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][1], 5);
+        b2_mantissas[i][2] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][2], 5);
+
+        /* bap=4 mantissas */
+        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
+        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
+    }
+    /* generate ungrouped mantissa tables
+       reference: Tables 7.21 and 7.23 */
+    for (i = 0; i < 7; i++) {
+        /* bap=3 mantissas */
+        b3_mantissas[i] = symmetric_dequant(i, 7);
+    }
+    for (i = 0; i < 15; i++) {
+        /* bap=5 mantissas */
+        b5_mantissas[i] = symmetric_dequant(i, 15);
+    }
+
+    /* generate dynamic range table
+       reference: Section 7.7.1 Dynamic Range Control */
+    for (i = 0; i < 256; i++) {
+        int v = (i >> 5) - ((i >> 7) << 3) - 5;
+        dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
+    }
+}
+
+/**
+ * AVCodec initialization
+ */
+static av_cold int ac3_decode_init(AVCodecContext *avctx)
+{
+    AC3DecodeContext *s = avctx->priv_data;
+    int i;
+
+    s->avctx = avctx;
+
+    ff_ac3_common_init();
+    ac3_tables_init();
+    ff_mdct_init(&s->imdct_256, 8, 1, 1.0);
+    ff_mdct_init(&s->imdct_512, 9, 1, 1.0);
+    ff_kbd_window_init(s->window, 5.0, 256);
+    ff_dsputil_init(&s->dsp, avctx);
+    avpriv_float_dsp_init(&s->fdsp, avctx->flags & CODEC_FLAG_BITEXACT);
+    ff_ac3dsp_init(&s->ac3dsp, avctx->flags & CODEC_FLAG_BITEXACT);
+    ff_fmt_convert_init(&s->fmt_conv, avctx);
+    av_lfg_init(&s->dith_state, 0);
+
+    avctx->sample_fmt = AV_SAMPLE_FMT_FLTP;
+
+    /* allow downmixing to stereo or mono */
+    if (avctx->channels > 0 && avctx->request_channels > 0 &&
+            avctx->request_channels < avctx->channels &&
+            avctx->request_channels <= 2) {
+        avctx->channels = avctx->request_channels;
+    }
+    s->downmixed = 1;
+
+    for (i = 0; i < AC3_MAX_CHANNELS; i++) {
+        s->xcfptr[i] = s->transform_coeffs[i];
+        s->dlyptr[i] = s->delay[i];
+    }
+
+    return 0;
+}
+
+/**
+ * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
+ * GetBitContext within AC3DecodeContext must point to
+ * the start of the synchronized AC-3 bitstream.
+ */
+static int ac3_parse_header(AC3DecodeContext *s)
+{
+    GetBitContext *gbc = &s->gbc;
+    int i;
+
+    /* read the rest of the bsi. read twice for dual mono mode. */
+    i = !s->channel_mode;
+    do {
+        skip_bits(gbc, 5); // skip dialog normalization
+        if (get_bits1(gbc))
+            skip_bits(gbc, 8); //skip compression
+        if (get_bits1(gbc))
+            skip_bits(gbc, 8); //skip language code
+        if (get_bits1(gbc))
+            skip_bits(gbc, 7); //skip audio production information
+    } while (i--);
+
+    skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
+
+    /* skip the timecodes (or extra bitstream information for Alternate Syntax)
+       TODO: read & use the xbsi1 downmix levels */
+    if (get_bits1(gbc))
+        skip_bits(gbc, 14); //skip timecode1 / xbsi1
+    if (get_bits1(gbc))
+        skip_bits(gbc, 14); //skip timecode2 / xbsi2
+
+    /* skip additional bitstream info */
+    if (get_bits1(gbc)) {
+        i = get_bits(gbc, 6);
+        do {
+            skip_bits(gbc, 8);
+        } while (i--);
+    }
+
+    return 0;
+}
+
+/**
+ * Common function to parse AC-3 or E-AC-3 frame header
+ */
+static int parse_frame_header(AC3DecodeContext *s)
+{
+    AC3HeaderInfo hdr;
+    int err;
+
+    err = avpriv_ac3_parse_header(&s->gbc, &hdr);
+    if (err)
+        return err;
+
+    /* get decoding parameters from header info */
+    s->bit_alloc_params.sr_code     = hdr.sr_code;
+    s->bitstream_mode               = hdr.bitstream_mode;
+    s->channel_mode                 = hdr.channel_mode;
+    s->channel_layout               = hdr.channel_layout;
+    s->lfe_on                       = hdr.lfe_on;
+    s->bit_alloc_params.sr_shift    = hdr.sr_shift;
+    s->sample_rate                  = hdr.sample_rate;
+    s->bit_rate                     = hdr.bit_rate;
+    s->channels                     = hdr.channels;
+    s->fbw_channels                 = s->channels - s->lfe_on;
+    s->lfe_ch                       = s->fbw_channels + 1;
+    s->frame_size                   = hdr.frame_size;
+    s->center_mix_level             = hdr.center_mix_level;
+    s->surround_mix_level           = hdr.surround_mix_level;
+    s->num_blocks                   = hdr.num_blocks;
+    s->frame_type                   = hdr.frame_type;
+    s->substreamid                  = hdr.substreamid;
+
+    if (s->lfe_on) {
+        s->start_freq[s->lfe_ch]     = 0;
+        s->end_freq[s->lfe_ch]       = 7;
+        s->num_exp_groups[s->lfe_ch] = 2;
+        s->channel_in_cpl[s->lfe_ch] = 0;
+    }
+
+    if (hdr.bitstream_id <= 10) {
+        s->eac3                  = 0;
+        s->snr_offset_strategy   = 2;
+        s->block_switch_syntax   = 1;
+        s->dither_flag_syntax    = 1;
+        s->bit_allocation_syntax = 1;
+        s->fast_gain_syntax      = 0;
+        s->first_cpl_leak        = 0;
+        s->dba_syntax            = 1;
+        s->skip_syntax           = 1;
+        memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
+        return ac3_parse_header(s);
+    } else if (CONFIG_EAC3_DECODER) {
+        s->eac3 = 1;
+        return ff_eac3_parse_header(s);
+    } else {
+        av_log(s->avctx, AV_LOG_ERROR, "E-AC-3 support not compiled in\n");
+        return -1;
+    }
+}
+
+/**
+ * Set stereo downmixing coefficients based on frame header info.
+ * reference: Section 7.8.2 Downmixing Into Two Channels
+ */
+static void set_downmix_coeffs(AC3DecodeContext *s)
+{
+    int i;
+    float cmix = gain_levels[s->  center_mix_level];
+    float smix = gain_levels[s->surround_mix_level];
+    float norm0, norm1;
+
+    for (i = 0; i < s->fbw_channels; i++) {
+        s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
+        s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
+    }
+    if (s->channel_mode > 1 && s->channel_mode & 1) {
+        s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
+    }
+    if (s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
+        int nf = s->channel_mode - 2;
+        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
+    }
+    if (s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
+        int nf = s->channel_mode - 4;
+        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
+    }
+
+    /* renormalize */
+    norm0 = norm1 = 0.0;
+    for (i = 0; i < s->fbw_channels; i++) {
+        norm0 += s->downmix_coeffs[i][0];
+        norm1 += s->downmix_coeffs[i][1];
+    }
+    norm0 = 1.0f / norm0;
+    norm1 = 1.0f / norm1;
+    for (i = 0; i < s->fbw_channels; i++) {
+        s->downmix_coeffs[i][0] *= norm0;
+        s->downmix_coeffs[i][1] *= norm1;
+    }
+
+    if (s->output_mode == AC3_CHMODE_MONO) {
+        for (i = 0; i < s->fbw_channels; i++)
+            s->downmix_coeffs[i][0] = (s->downmix_coeffs[i][0] +
+                                       s->downmix_coeffs[i][1]) * LEVEL_MINUS_3DB;
+    }
+}
+
+/**
+ * Decode the grouped exponents according to exponent strategy.
+ * reference: Section 7.1.3 Exponent Decoding
+ */
+static int decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
+                            uint8_t absexp, int8_t *dexps)
+{
+    int i, j, grp, group_size;
+    int dexp[256];
+    int expacc, prevexp;
+
+    /* unpack groups */
+    group_size = exp_strategy + (exp_strategy == EXP_D45);
+    for (grp = 0, i = 0; grp < ngrps; grp++) {
+        expacc = get_bits(gbc, 7);
+        dexp[i++] = ungroup_3_in_7_bits_tab[expacc][0];
+        dexp[i++] = ungroup_3_in_7_bits_tab[expacc][1];
+        dexp[i++] = ungroup_3_in_7_bits_tab[expacc][2];
+    }
+
+    /* convert to absolute exps and expand groups */
+    prevexp = absexp;
+    for (i = 0, j = 0; i < ngrps * 3; i++) {
+        prevexp += dexp[i] - 2;
+        if (prevexp > 24U)
+            return -1;
+        switch (group_size) {
+        case 4: dexps[j++] = prevexp;
+                dexps[j++] = prevexp;
+        case 2: dexps[j++] = prevexp;
+        case 1: dexps[j++] = prevexp;
+        }
+    }
+    return 0;
+}
+
+/**
+ * Generate transform coefficients for each coupled channel in the coupling
+ * range using the coupling coefficients and coupling coordinates.
+ * reference: Section 7.4.3 Coupling Coordinate Format
+ */
+static void calc_transform_coeffs_cpl(AC3DecodeContext *s)
+{
+    int bin, band, ch;
+
+    bin = s->start_freq[CPL_CH];
+    for (band = 0; band < s->num_cpl_bands; band++) {
+        int band_start = bin;
+        int band_end = bin + s->cpl_band_sizes[band];
+        for (ch = 1; ch <= s->fbw_channels; ch++) {
+            if (s->channel_in_cpl[ch]) {
+                int cpl_coord = s->cpl_coords[ch][band] << 5;
+                for (bin = band_start; bin < band_end; bin++) {
+                    s->fixed_coeffs[ch][bin] =
+                        MULH(s->fixed_coeffs[CPL_CH][bin] << 4, cpl_coord);
+                }
+                if (ch == 2 && s->phase_flags[band]) {
+                    for (bin = band_start; bin < band_end; bin++)
+                        s->fixed_coeffs[2][bin] = -s->fixed_coeffs[2][bin];
+                }
+            }
+        }
+        bin = band_end;
+    }
+}
+
+/**
+ * Grouped mantissas for 3-level 5-level and 11-level quantization
+ */
+typedef struct {
+    int b1_mant[2];
+    int b2_mant[2];
+    int b4_mant;
+    int b1;
+    int b2;
+    int b4;
+} mant_groups;
+
+/**
+ * Decode the transform coefficients for a particular channel
+ * reference: Section 7.3 Quantization and Decoding of Mantissas
+ */
+static void ac3_decode_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
+{
+    int start_freq = s->start_freq[ch_index];
+    int end_freq   = s->end_freq[ch_index];
+    uint8_t *baps  = s->bap[ch_index];
+    int8_t *exps   = s->dexps[ch_index];
+    int *coeffs    = s->fixed_coeffs[ch_index];
+    int dither     = (ch_index == CPL_CH) || s->dither_flag[ch_index];
+    GetBitContext *gbc = &s->gbc;
+    int freq;
+
+    for (freq = start_freq; freq < end_freq; freq++) {
+        int bap = baps[freq];
+        int mantissa;
+        switch (bap) {
+        case 0:
+            /* random noise with approximate range of -0.707 to 0.707 */
+            if (dither)
+                mantissa = (((av_lfg_get(&s->dith_state)>>8)*181)>>8) - 5931008;
+            else
+                mantissa = 0;
+            break;
+        case 1:
+            if (m->b1) {
+                m->b1--;
+                mantissa = m->b1_mant[m->b1];
+            } else {
+                int bits      = get_bits(gbc, 5);
+                mantissa      = b1_mantissas[bits][0];
+                m->b1_mant[1] = b1_mantissas[bits][1];
+                m->b1_mant[0] = b1_mantissas[bits][2];
+                m->b1         = 2;
+            }
+            break;
+        case 2:
+            if (m->b2) {
+                m->b2--;
+                mantissa = m->b2_mant[m->b2];
+            } else {
+                int bits      = get_bits(gbc, 7);
+                mantissa      = b2_mantissas[bits][0];
+                m->b2_mant[1] = b2_mantissas[bits][1];
+                m->b2_mant[0] = b2_mantissas[bits][2];
+                m->b2         = 2;
+            }
+            break;
+        case 3:
+            mantissa = b3_mantissas[get_bits(gbc, 3)];
+            break;
+        case 4:
+            if (m->b4) {
+                m->b4 = 0;
+                mantissa = m->b4_mant;
+            } else {
+                int bits   = get_bits(gbc, 7);
+                mantissa   = b4_mantissas[bits][0];
+                m->b4_mant = b4_mantissas[bits][1];
+                m->b4      = 1;
+            }
+            break;
+        case 5:
+            mantissa = b5_mantissas[get_bits(gbc, 4)];
+            break;
+        default: /* 6 to 15 */
+            /* Shift mantissa and sign-extend it. */
+            mantissa = get_sbits(gbc, quantization_tab[bap]);
+            mantissa <<= 24 - quantization_tab[bap];
+            break;
+        }
+        coeffs[freq] = mantissa >> exps[freq];
+    }
+}
+
+/**
+ * Remove random dithering from coupling range coefficients with zero-bit
+ * mantissas for coupled channels which do not use dithering.
+ * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
+ */
+static void remove_dithering(AC3DecodeContext *s) {
+    int ch, i;
+
+    for (ch = 1; ch <= s->fbw_channels; ch++) {
+        if (!s->dither_flag[ch] && s->channel_in_cpl[ch]) {
+            for (i = s->start_freq[CPL_CH]; i < s->end_freq[CPL_CH]; i++) {
+                if (!s->bap[CPL_CH][i])
+                    s->fixed_coeffs[ch][i] = 0;
+            }
+        }
+    }
+}
+
+static void decode_transform_coeffs_ch(AC3DecodeContext *s, int blk, int ch,
+                                       mant_groups *m)
+{
+    if (!s->channel_uses_aht[ch]) {
+        ac3_decode_transform_coeffs_ch(s, ch, m);
+    } else {
+        /* if AHT is used, mantissas for all blocks are encoded in the first
+           block of the frame. */
+        int bin;
+        if (!blk && CONFIG_EAC3_DECODER)
+            ff_eac3_decode_transform_coeffs_aht_ch(s, ch);
+        for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
+            s->fixed_coeffs[ch][bin] = s->pre_mantissa[ch][bin][blk] >> s->dexps[ch][bin];
+        }
+    }
+}
+
+/**
+ * Decode the transform coefficients.
+ */
+static void decode_transform_coeffs(AC3DecodeContext *s, int blk)
+{
+    int ch, end;
+    int got_cplchan = 0;
+    mant_groups m;
+
+    m.b1 = m.b2 = m.b4 = 0;
+
+    for (ch = 1; ch <= s->channels; ch++) {
+        /* transform coefficients for full-bandwidth channel */
+        decode_transform_coeffs_ch(s, blk, ch, &m);
+        /* transform coefficients for coupling channel come right after the
+           coefficients for the first coupled channel*/
+        if (s->channel_in_cpl[ch])  {
+            if (!got_cplchan) {
+                decode_transform_coeffs_ch(s, blk, CPL_CH, &m);
+                calc_transform_coeffs_cpl(s);
+                got_cplchan = 1;
+            }
+            end = s->end_freq[CPL_CH];
+        } else {
+            end = s->end_freq[ch];
+        }
+        do
+            s->fixed_coeffs[ch][end] = 0;
+        while (++end < 256);
+    }
+
+    /* zero the dithered coefficients for appropriate channels */
+    remove_dithering(s);
+}
+
+/**
+ * Stereo rematrixing.
+ * reference: Section 7.5.4 Rematrixing : Decoding Technique
+ */
+static void do_rematrixing(AC3DecodeContext *s)
+{
+    int bnd, i;
+    int end, bndend;
+
+    end = FFMIN(s->end_freq[1], s->end_freq[2]);
+
+    for (bnd = 0; bnd < s->num_rematrixing_bands; bnd++) {
+        if (s->rematrixing_flags[bnd]) {
+            bndend = FFMIN(end, ff_ac3_rematrix_band_tab[bnd + 1]);
+            for (i = ff_ac3_rematrix_band_tab[bnd]; i < bndend; i++) {
+                int tmp0 = s->fixed_coeffs[1][i];
+                s->fixed_coeffs[1][i] += s->fixed_coeffs[2][i];
+                s->fixed_coeffs[2][i]  = tmp0 - s->fixed_coeffs[2][i];
+            }
+        }
+    }
+}
+
+/**
+ * Inverse MDCT Transform.
+ * Convert frequency domain coefficients to time-domain audio samples.
+ * reference: Section 7.9.4 Transformation Equations
+ */
+static inline void do_imdct(AC3DecodeContext *s, int channels)
+{
+    int ch;
+
+    for (ch = 1; ch <= channels; ch++) {
+        if (s->block_switch[ch]) {
+            int i;
+            float *x = s->tmp_output + 128;
+            for (i = 0; i < 128; i++)
+                x[i] = s->transform_coeffs[ch][2 * i];
+            s->imdct_256.imdct_half(&s->imdct_256, s->tmp_output, x);
+            s->fdsp.vector_fmul_window(s->outptr[ch - 1], s->delay[ch - 1],
+                                       s->tmp_output, s->window, 128);
+            for (i = 0; i < 128; i++)
+                x[i] = s->transform_coeffs[ch][2 * i + 1];
+            s->imdct_256.imdct_half(&s->imdct_256, s->delay[ch - 1], x);
+        } else {
+            s->imdct_512.imdct_half(&s->imdct_512, s->tmp_output, s->transform_coeffs[ch]);
+            s->fdsp.vector_fmul_window(s->outptr[ch - 1], s->delay[ch - 1],
+                                       s->tmp_output, s->window, 128);
+            memcpy(s->delay[ch - 1], s->tmp_output + 128, 128 * sizeof(float));
+        }
+    }
+}
+
+/**
+ * Upmix delay samples from stereo to original channel layout.
+ */
+static void ac3_upmix_delay(AC3DecodeContext *s)
+{
+    int channel_data_size = sizeof(s->delay[0]);
+    switch (s->channel_mode) {
+    case AC3_CHMODE_DUALMONO:
+    case AC3_CHMODE_STEREO:
+        /* upmix mono to stereo */
+        memcpy(s->delay[1], s->delay[0], channel_data_size);
+        break;
+    case AC3_CHMODE_2F2R:
+        memset(s->delay[3], 0, channel_data_size);
+    case AC3_CHMODE_2F1R:
+        memset(s->delay[2], 0, channel_data_size);
+        break;
+    case AC3_CHMODE_3F2R:
+        memset(s->delay[4], 0, channel_data_size);
+    case AC3_CHMODE_3F1R:
+        memset(s->delay[3], 0, channel_data_size);
+    case AC3_CHMODE_3F:
+        memcpy(s->delay[2], s->delay[1], channel_data_size);
+        memset(s->delay[1], 0, channel_data_size);
+        break;
+    }
+}
+
+/**
+ * Decode band structure for coupling, spectral extension, or enhanced coupling.
+ * The band structure defines how many subbands are in each band.  For each
+ * subband in the range, 1 means it is combined with the previous band, and 0
+ * means that it starts a new band.
+ *
+ * @param[in] gbc bit reader context
+ * @param[in] blk block number
+ * @param[in] eac3 flag to indicate E-AC-3
+ * @param[in] ecpl flag to indicate enhanced coupling
+ * @param[in] start_subband subband number for start of range
+ * @param[in] end_subband subband number for end of range
+ * @param[in] default_band_struct default band structure table
+ * @param[out] num_bands number of bands (optionally NULL)
+ * @param[out] band_sizes array containing the number of bins in each band (optionally NULL)
+ */
+static void decode_band_structure(GetBitContext *gbc, int blk, int eac3,
+                                  int ecpl, int start_subband, int end_subband,
+                                  const uint8_t *default_band_struct,
+                                  int *num_bands, uint8_t *band_sizes)
+{
+    int subbnd, bnd, n_subbands, n_bands=0;
+    uint8_t bnd_sz[22];
+    uint8_t coded_band_struct[22];
+    const uint8_t *band_struct;
+
+    n_subbands = end_subband - start_subband;
+
+    /* decode band structure from bitstream or use default */
+    if (!eac3 || get_bits1(gbc)) {
+        for (subbnd = 0; subbnd < n_subbands - 1; subbnd++) {
+            coded_band_struct[subbnd] = get_bits1(gbc);
+        }
+        band_struct = coded_band_struct;
+    } else if (!blk) {
+        band_struct = &default_band_struct[start_subband+1];
+    } else {
+        /* no change in band structure */
+        return;
+    }
+
+    /* calculate number of bands and band sizes based on band structure.
+       note that the first 4 subbands in enhanced coupling span only 6 bins
+       instead of 12. */
+    if (num_bands || band_sizes ) {
+        n_bands = n_subbands;
+        bnd_sz[0] = ecpl ? 6 : 12;
+        for (bnd = 0, subbnd = 1; subbnd < n_subbands; subbnd++) {
+            int subbnd_size = (ecpl && subbnd < 4) ? 6 : 12;
+            if (band_struct[subbnd - 1]) {
+                n_bands--;
+                bnd_sz[bnd] += subbnd_size;
+            } else {
+                bnd_sz[++bnd] = subbnd_size;
+            }
+        }
+    }
+
+    /* set optional output params */
+    if (num_bands)
+        *num_bands = n_bands;
+    if (band_sizes)
+        memcpy(band_sizes, bnd_sz, n_bands);
+}
+
+/**
+ * Decode a single audio block from the AC-3 bitstream.
+ */
+static int decode_audio_block(AC3DecodeContext *s, int blk)
+{
+    int fbw_channels = s->fbw_channels;
+    int channel_mode = s->channel_mode;
+    int i, bnd, seg, ch;
+    int different_transforms;
+    int downmix_output;
+    int cpl_in_use;
+    GetBitContext *gbc = &s->gbc;
+    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS] = { 0 };
+
+    /* block switch flags */
+    different_transforms = 0;
+    if (s->block_switch_syntax) {
+        for (ch = 1; ch <= fbw_channels; ch++) {
+            s->block_switch[ch] = get_bits1(gbc);
+            if (ch > 1 && s->block_switch[ch] != s->block_switch[1])
+                different_transforms = 1;
+        }
+    }
+
+    /* dithering flags */
+    if (s->dither_flag_syntax) {
+        for (ch = 1; ch <= fbw_channels; ch++) {
+            s->dither_flag[ch] = get_bits1(gbc);
+        }
+    }
+
+    /* dynamic range */
+    i = !s->channel_mode;
+    do {
+        if (get_bits1(gbc)) {
+            s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)] - 1.0) *
+                                  s->drc_scale) + 1.0;
+        } else if (blk == 0) {
+            s->dynamic_range[i] = 1.0f;
+        }
+    } while (i--);
+
+    /* spectral extension strategy */
+    if (s->eac3 && (!blk || get_bits1(gbc))) {
+        s->spx_in_use = get_bits1(gbc);
+        if (s->spx_in_use) {
+            int dst_start_freq, dst_end_freq, src_start_freq,
+                start_subband, end_subband;
+
+            /* determine which channels use spx */
+            if (s->channel_mode == AC3_CHMODE_MONO) {
+                s->channel_uses_spx[1] = 1;
+            } else {
+                for (ch = 1; ch <= fbw_channels; ch++)
+                    s->channel_uses_spx[ch] = get_bits1(gbc);
+            }
+
+            /* get the frequency bins of the spx copy region and the spx start
+               and end subbands */
+            dst_start_freq = get_bits(gbc, 2);
+            start_subband  = get_bits(gbc, 3) + 2;
+            if (start_subband > 7)
+                start_subband += start_subband - 7;
+            end_subband    = get_bits(gbc, 3) + 5;
+            if (end_subband   > 7)
+                end_subband   += end_subband   - 7;
+            dst_start_freq = dst_start_freq * 12 + 25;
+            src_start_freq = start_subband  * 12 + 25;
+            dst_end_freq   = end_subband    * 12 + 25;
+
+            /* check validity of spx ranges */
+            if (start_subband >= end_subband) {
+                av_log(s->avctx, AV_LOG_ERROR, "invalid spectral extension "
+                       "range (%d >= %d)\n", start_subband, end_subband);
+                return -1;
+            }
+            if (dst_start_freq >= src_start_freq) {
+                av_log(s->avctx, AV_LOG_ERROR, "invalid spectral extension "
+                       "copy start bin (%d >= %d)\n", dst_start_freq, src_start_freq);
+                return -1;
+            }
+
+            s->spx_dst_start_freq = dst_start_freq;
+            s->spx_src_start_freq = src_start_freq;
+            s->spx_dst_end_freq   = dst_end_freq;
+
+            decode_band_structure(gbc, blk, s->eac3, 0,
+                                  start_subband, end_subband,
+                                  ff_eac3_default_spx_band_struct,
+                                  &s->num_spx_bands,
+                                  s->spx_band_sizes);
+        } else {
+            for (ch = 1; ch <= fbw_channels; ch++) {
+                s->channel_uses_spx[ch] = 0;
+                s->first_spx_coords[ch] = 1;
+            }
+        }
+    }
+
+    /* spectral extension coordinates */
+    if (s->spx_in_use) {
+        for (ch = 1; ch <= fbw_channels; ch++) {
+            if (s->channel_uses_spx[ch]) {
+                if (s->first_spx_coords[ch] || get_bits1(gbc)) {
+                    float spx_blend;
+                    int bin, master_spx_coord;
+
+                    s->first_spx_coords[ch] = 0;
+                    spx_blend = get_bits(gbc, 5) * (1.0f/32);
+                    master_spx_coord = get_bits(gbc, 2) * 3;
+
+                    bin = s->spx_src_start_freq;
+                    for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
+                        int bandsize;
+                        int spx_coord_exp, spx_coord_mant;
+                        float nratio, sblend, nblend, spx_coord;
+
+                        /* calculate blending factors */
+                        bandsize = s->spx_band_sizes[bnd];
+                        nratio = ((float)((bin + (bandsize >> 1))) / s->spx_dst_end_freq) - spx_blend;
+                        nratio = av_clipf(nratio, 0.0f, 1.0f);
+                        nblend = sqrtf(3.0f * nratio); // noise is scaled by sqrt(3)
+                                                       // to give unity variance
+                        sblend = sqrtf(1.0f - nratio);
+                        bin += bandsize;
+
+                        /* decode spx coordinates */
+                        spx_coord_exp  = get_bits(gbc, 4);
+                        spx_coord_mant = get_bits(gbc, 2);
+                        if (spx_coord_exp == 15) spx_coord_mant <<= 1;
+                        else                     spx_coord_mant += 4;
+                        spx_coord_mant <<= (25 - spx_coord_exp - master_spx_coord);
+                        spx_coord = spx_coord_mant * (1.0f / (1 << 23));
+
+                        /* multiply noise and signal blending factors by spx coordinate */
+                        s->spx_noise_blend [ch][bnd] = nblend * spx_coord;
+                        s->spx_signal_blend[ch][bnd] = sblend * spx_coord;
+                    }
+                }
+            } else {
+                s->first_spx_coords[ch] = 1;
+            }
+        }
+    }
+
+    /* coupling strategy */
+    if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {
+        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
+        if (!s->eac3)
+            s->cpl_in_use[blk] = get_bits1(gbc);
+        if (s->cpl_in_use[blk]) {
+            /* coupling in use */
+            int cpl_start_subband, cpl_end_subband;
+
+            if (channel_mode < AC3_CHMODE_STEREO) {
+                av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
+                return -1;
+            }
+
+            /* check for enhanced coupling */
+            if (s->eac3 && get_bits1(gbc)) {
+                /* TODO: parse enhanced coupling strategy info */
+                avpriv_request_sample(s->avctx, "Enhanced coupling");
+                return AVERROR_PATCHWELCOME;
+            }
+
+            /* determine which channels are coupled */
+            if (s->eac3 && s->channel_mode == AC3_CHMODE_STEREO) {
+                s->channel_in_cpl[1] = 1;
+                s->channel_in_cpl[2] = 1;
+            } else {
+                for (ch = 1; ch <= fbw_channels; ch++)
+                    s->channel_in_cpl[ch] = get_bits1(gbc);
+            }
+
+            /* phase flags in use */
+            if (channel_mode == AC3_CHMODE_STEREO)
+                s->phase_flags_in_use = get_bits1(gbc);
+
+            /* coupling frequency range */
+            cpl_start_subband = get_bits(gbc, 4);
+            cpl_end_subband = s->spx_in_use ? (s->spx_src_start_freq - 37) / 12 :
+                                              get_bits(gbc, 4) + 3;
+            if (cpl_start_subband >= cpl_end_subband) {
+                av_log(s->avctx, AV_LOG_ERROR, "invalid coupling range (%d >= %d)\n",
+                       cpl_start_subband, cpl_end_subband);
+                return -1;
+            }
+            s->start_freq[CPL_CH] = cpl_start_subband * 12 + 37;
+            s->end_freq[CPL_CH]   = cpl_end_subband   * 12 + 37;
+
+            decode_band_structure(gbc, blk, s->eac3, 0, cpl_start_subband,
+                                  cpl_end_subband,
+                                  ff_eac3_default_cpl_band_struct,
+                                  &s->num_cpl_bands, s->cpl_band_sizes);
+        } else {
+            /* coupling not in use */
+            for (ch = 1; ch <= fbw_channels; ch++) {
+                s->channel_in_cpl[ch] = 0;
+                s->first_cpl_coords[ch] = 1;
+            }
+            s->first_cpl_leak = s->eac3;
+            s->phase_flags_in_use = 0;
+        }
+    } else if (!s->eac3) {
+        if (!blk) {
+            av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must "
+                   "be present in block 0\n");
+            return -1;
+        } else {
+            s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
+        }
+    }
+    cpl_in_use = s->cpl_in_use[blk];
+
+    /* coupling coordinates */
+    if (cpl_in_use) {
+        int cpl_coords_exist = 0;
+
+        for (ch = 1; ch <= fbw_channels; ch++) {
+            if (s->channel_in_cpl[ch]) {
+                if ((s->eac3 && s->first_cpl_coords[ch]) || get_bits1(gbc)) {
+                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
+                    s->first_cpl_coords[ch] = 0;
+                    cpl_coords_exist = 1;
+                    master_cpl_coord = 3 * get_bits(gbc, 2);
+                    for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
+                        cpl_coord_exp = get_bits(gbc, 4);
+                        cpl_coord_mant = get_bits(gbc, 4);
+                        if (cpl_coord_exp == 15)
+                            s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
+                        else
+                            s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
+                        s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
+                    }
+                } else if (!blk) {
+                    av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must "
+                           "be present in block 0\n");
+                    return -1;
+                }
+            } else {
+                /* channel not in coupling */
+                s->first_cpl_coords[ch] = 1;
+            }
+        }
+        /* phase flags */
+        if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
+            for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
+                s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
+            }
+        }
+    }
+
+    /* stereo rematrixing strategy and band structure */
+    if (channel_mode == AC3_CHMODE_STEREO) {
+        if ((s->eac3 && !blk) || get_bits1(gbc)) {
+            s->num_rematrixing_bands = 4;
+            if (cpl_in_use && s->start_freq[CPL_CH] <= 61) {
+                s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
+            } else if (s->spx_in_use && s->spx_src_start_freq <= 61) {
+                s->num_rematrixing_bands--;
+            }
+            for (bnd = 0; bnd < s->num_rematrixing_bands; bnd++)
+                s->rematrixing_flags[bnd] = get_bits1(gbc);
+        } else if (!blk) {
+            av_log(s->avctx, AV_LOG_WARNING, "Warning: "
+                   "new rematrixing strategy not present in block 0\n");
+            s->num_rematrixing_bands = 0;
+        }
+    }
+
+    /* exponent strategies for each channel */
+    for (ch = !cpl_in_use; ch <= s->channels; ch++) {
+        if (!s->eac3)
+            s->exp_strategy[blk][ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
+        if (s->exp_strategy[blk][ch] != EXP_REUSE)
+            bit_alloc_stages[ch] = 3;
+    }
+
+    /* channel bandwidth */
+    for (ch = 1; ch <= fbw_channels; ch++) {
+        s->start_freq[ch] = 0;
+        if (s->exp_strategy[blk][ch] != EXP_REUSE) {
+            int group_size;
+            int prev = s->end_freq[ch];
+            if (s->channel_in_cpl[ch])
+                s->end_freq[ch] = s->start_freq[CPL_CH];
+            else if (s->channel_uses_spx[ch])
+                s->end_freq[ch] = s->spx_src_start_freq;
+            else {
+                int bandwidth_code = get_bits(gbc, 6);
+                if (bandwidth_code > 60) {
+                    av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60\n", bandwidth_code);
+                    return -1;
+                }
+                s->end_freq[ch] = bandwidth_code * 3 + 73;
+            }
+            group_size = 3 << (s->exp_strategy[blk][ch] - 1);
+            s->num_exp_groups[ch] = (s->end_freq[ch] + group_size-4) / group_size;
+            if (blk > 0 && s->end_freq[ch] != prev)
+                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
+        }
+    }
+    if (cpl_in_use && s->exp_strategy[blk][CPL_CH] != EXP_REUSE) {
+        s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
+                                    (3 << (s->exp_strategy[blk][CPL_CH] - 1));
+    }
+
+    /* decode exponents for each channel */
+    for (ch = !cpl_in_use; ch <= s->channels; ch++) {
+        if (s->exp_strategy[blk][ch] != EXP_REUSE) {
+            s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
+            if (decode_exponents(gbc, s->exp_strategy[blk][ch],
+                                 s->num_exp_groups[ch], s->dexps[ch][0],
+                                 &s->dexps[ch][s->start_freq[ch]+!!ch])) {
+                av_log(s->avctx, AV_LOG_ERROR, "exponent out-of-range\n");
+                return -1;
+            }
+            if (ch != CPL_CH && ch != s->lfe_ch)
+                skip_bits(gbc, 2); /* skip gainrng */
+        }
+    }
+
+    /* bit allocation information */
+    if (s->bit_allocation_syntax) {
+        if (get_bits1(gbc)) {
+            s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
+            s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
+            s->bit_alloc_params.slow_gain  = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
+            s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
+            s->bit_alloc_params.floor  = ff_ac3_floor_tab[get_bits(gbc, 3)];
+            for (ch = !cpl_in_use; ch <= s->channels; ch++)
+                bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
+        } else if (!blk) {
+            av_log(s->avctx, AV_LOG_ERROR, "new bit allocation info must "
+                   "be present in block 0\n");
+            return -1;
+        }
+    }
+
+    /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
+    if (!s->eac3 || !blk) {
+        if (s->snr_offset_strategy && get_bits1(gbc)) {
+            int snr = 0;
+            int csnr;
+            csnr = (get_bits(gbc, 6) - 15) << 4;
+            for (i = ch = !cpl_in_use; ch <= s->channels; ch++) {
+                /* snr offset */
+                if (ch == i || s->snr_offset_strategy == 2)
+                    snr = (csnr + get_bits(gbc, 4)) << 2;
+                /* run at least last bit allocation stage if snr offset changes */
+                if (blk && s->snr_offset[ch] != snr) {
+                    bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 1);
+                }
+                s->snr_offset[ch] = snr;
+
+                /* fast gain (normal AC-3 only) */
+                if (!s->eac3) {
+                    int prev = s->fast_gain[ch];
+                    s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
+                    /* run last 2 bit allocation stages if fast gain changes */
+                    if (blk && prev != s->fast_gain[ch])
+                        bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
+                }
+            }
+        } else if (!s->eac3 && !blk) {
+            av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
+            return -1;
+        }
+    }
+
+    /* fast gain (E-AC-3 only) */
+    if (s->fast_gain_syntax && get_bits1(gbc)) {
+        for (ch = !cpl_in_use; ch <= s->channels; ch++) {
+            int prev = s->fast_gain[ch];
+            s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
+            /* run last 2 bit allocation stages if fast gain changes */
+            if (blk && prev != s->fast_gain[ch])
+                bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
+        }
+    } else if (s->eac3 && !blk) {
+        for (ch = !cpl_in_use; ch <= s->channels; ch++)
+            s->fast_gain[ch] = ff_ac3_fast_gain_tab[4];
+    }
+
+    /* E-AC-3 to AC-3 converter SNR offset */
+    if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && get_bits1(gbc)) {
+        skip_bits(gbc, 10); // skip converter snr offset
+    }
+
+    /* coupling leak information */
+    if (cpl_in_use) {
+        if (s->first_cpl_leak || get_bits1(gbc)) {
+            int fl = get_bits(gbc, 3);
+            int sl = get_bits(gbc, 3);
+            /* run last 2 bit allocation stages for coupling channel if
+               coupling leak changes */
+            if (blk && (fl != s->bit_alloc_params.cpl_fast_leak ||
+                sl != s->bit_alloc_params.cpl_slow_leak)) {
+                bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
+            }
+            s->bit_alloc_params.cpl_fast_leak = fl;
+            s->bit_alloc_params.cpl_slow_leak = sl;
+        } else if (!s->eac3 && !blk) {
+            av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must "
+                   "be present in block 0\n");
+            return -1;
+        }
+        s->first_cpl_leak = 0;
+    }
+
+    /* delta bit allocation information */
+    if (s->dba_syntax && get_bits1(gbc)) {
+        /* delta bit allocation exists (strategy) */
+        for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
+            s->dba_mode[ch] = get_bits(gbc, 2);
+            if (s->dba_mode[ch] == DBA_RESERVED) {
+                av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
+                return -1;
+            }
+            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
+        }
+        /* channel delta offset, len and bit allocation */
+        for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
+            if (s->dba_mode[ch] == DBA_NEW) {
+                s->dba_nsegs[ch] = get_bits(gbc, 3) + 1;
+                for (seg = 0; seg < s->dba_nsegs[ch]; seg++) {
+                    s->dba_offsets[ch][seg] = get_bits(gbc, 5);
+                    s->dba_lengths[ch][seg] = get_bits(gbc, 4);
+                    s->dba_values[ch][seg]  = get_bits(gbc, 3);
+                }
+                /* run last 2 bit allocation stages if new dba values */
+                bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
+            }
+        }
+    } else if (blk == 0) {
+        for (ch = 0; ch <= s->channels; ch++) {
+            s->dba_mode[ch] = DBA_NONE;
+        }
+    }
+
+    /* Bit allocation */
+    for (ch = !cpl_in_use; ch <= s->channels; ch++) {
+        if (bit_alloc_stages[ch] > 2) {
+            /* Exponent mapping into PSD and PSD integration */
+            ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
+                                      s->start_freq[ch], s->end_freq[ch],
+                                      s->psd[ch], s->band_psd[ch]);
+        }
+        if (bit_alloc_stages[ch] > 1) {
+            /* Compute excitation function, Compute masking curve, and
+               Apply delta bit allocation */
+            if (ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
+                                           s->start_freq[ch],  s->end_freq[ch],
+                                           s->fast_gain[ch],   (ch == s->lfe_ch),
+                                           s->dba_mode[ch],    s->dba_nsegs[ch],
+                                           s->dba_offsets[ch], s->dba_lengths[ch],
+                                           s->dba_values[ch],  s->mask[ch])) {
+                av_log(s->avctx, AV_LOG_ERROR, "error in bit allocation\n");
+                return -1;
+            }
+        }
+        if (bit_alloc_stages[ch] > 0) {
+            /* Compute bit allocation */
+            const uint8_t *bap_tab = s->channel_uses_aht[ch] ?
+                                     ff_eac3_hebap_tab : ff_ac3_bap_tab;
+            s->ac3dsp.bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
+                                      s->start_freq[ch], s->end_freq[ch],
+                                      s->snr_offset[ch],
+                                      s->bit_alloc_params.floor,
+                                      bap_tab, s->bap[ch]);
+        }
+    }
+
+    /* unused dummy data */
+    if (s->skip_syntax && get_bits1(gbc)) {
+        int skipl = get_bits(gbc, 9);
+        while (skipl--)
+            skip_bits(gbc, 8);
+    }
+
+    /* unpack the transform coefficients
+       this also uncouples channels if coupling is in use. */
+    decode_transform_coeffs(s, blk);
+
+    /* TODO: generate enhanced coupling coordinates and uncouple */
+
+    /* recover coefficients if rematrixing is in use */
+    if (s->channel_mode == AC3_CHMODE_STEREO)
+        do_rematrixing(s);
+
+    /* apply scaling to coefficients (headroom, dynrng) */
+    for (ch = 1; ch <= s->channels; ch++) {
+        float gain = 1.0 / 4194304.0f;
+        if (s->channel_mode == AC3_CHMODE_DUALMONO) {
+            gain *= s->dynamic_range[2 - ch];
+        } else {
+            gain *= s->dynamic_range[0];
+        }
+        s->fmt_conv.int32_to_float_fmul_scalar(s->transform_coeffs[ch],
+                                               s->fixed_coeffs[ch], gain, 256);
+    }
+
+    /* apply spectral extension to high frequency bins */
+    if (s->spx_in_use && CONFIG_EAC3_DECODER) {
+        ff_eac3_apply_spectral_extension(s);
+    }
+
+    /* downmix and MDCT. order depends on whether block switching is used for
+       any channel in this block. this is because coefficients for the long
+       and short transforms cannot be mixed. */
+    downmix_output = s->channels != s->out_channels &&
+                     !((s->output_mode & AC3_OUTPUT_LFEON) &&
+                     s->fbw_channels == s->out_channels);
+    if (different_transforms) {
+        /* the delay samples have already been downmixed, so we upmix the delay
+           samples in order to reconstruct all channels before downmixing. */
+        if (s->downmixed) {
+            s->downmixed = 0;
+            ac3_upmix_delay(s);
+        }
+
+        do_imdct(s, s->channels);
+
+        if (downmix_output) {
+            s->ac3dsp.downmix(s->outptr, s->downmix_coeffs,
+                              s->out_channels, s->fbw_channels, 256);
+        }
+    } else {
+        if (downmix_output) {
+            s->ac3dsp.downmix(s->xcfptr + 1, s->downmix_coeffs,
+                              s->out_channels, s->fbw_channels, 256);
+        }
+
+        if (downmix_output && !s->downmixed) {
+            s->downmixed = 1;
+            s->ac3dsp.downmix(s->dlyptr, s->downmix_coeffs, s->out_channels,
+                              s->fbw_channels, 128);
+        }
+
+        do_imdct(s, s->out_channels);
+    }
+
+    return 0;
+}
+
+/**
+ * Decode a single AC-3 frame.
+ */
+static int ac3_decode_frame(AVCodecContext * avctx, void *data,
+                            int *got_frame_ptr, AVPacket *avpkt)
+{
+    AVFrame *frame     = data;
+    const uint8_t *buf = avpkt->data;
+    int buf_size = avpkt->size;
+    AC3DecodeContext *s = avctx->priv_data;
+    int blk, ch, err, ret;
+    const uint8_t *channel_map;
+    const float *output[AC3_MAX_CHANNELS];
+
+    /* copy input buffer to decoder context to avoid reading past the end
+       of the buffer, which can be caused by a damaged input stream. */
+    if (buf_size >= 2 && AV_RB16(buf) == 0x770B) {
+        // seems to be byte-swapped AC-3
+        int cnt = FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE) >> 1;
+        s->dsp.bswap16_buf((uint16_t *)s->input_buffer, (const uint16_t *)buf, cnt);
+    } else
+        memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE));
+    buf = s->input_buffer;
+    /* initialize the GetBitContext with the start of valid AC-3 Frame */
+    init_get_bits(&s->gbc, buf, buf_size * 8);
+
+    /* parse the syncinfo */
+    err = parse_frame_header(s);
+
+    if (err) {
+        switch (err) {
+        case AAC_AC3_PARSE_ERROR_SYNC:
+            av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
+            return -1;
+        case AAC_AC3_PARSE_ERROR_BSID:
+            av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
+            break;
+        case AAC_AC3_PARSE_ERROR_SAMPLE_RATE:
+            av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
+            break;
+        case AAC_AC3_PARSE_ERROR_FRAME_SIZE:
+            av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
+            break;
+        case AAC_AC3_PARSE_ERROR_FRAME_TYPE:
+            /* skip frame if CRC is ok. otherwise use error concealment. */
+            /* TODO: add support for substreams and dependent frames */
+            if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT || s->substreamid) {
+                av_log(avctx, AV_LOG_ERROR, "unsupported frame type : "
+                       "skipping frame\n");
+                *got_frame_ptr = 0;
+                return s->frame_size;
+            } else {
+                av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
+            }
+            break;
+        default:
+            av_log(avctx, AV_LOG_ERROR, "invalid header\n");
+            break;
+        }
+    } else {
+        /* check that reported frame size fits in input buffer */
+        if (s->frame_size > buf_size) {
+            av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
+            err = AAC_AC3_PARSE_ERROR_FRAME_SIZE;
+        } else if (avctx->err_recognition & (AV_EF_CRCCHECK|AV_EF_CAREFUL)) {
+            /* check for crc mismatch */
+            if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2],
+                       s->frame_size - 2)) {
+                av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
+                err = AAC_AC3_PARSE_ERROR_CRC;
+            }
+        }
+    }
+
+    /* if frame is ok, set audio parameters */
+    if (!err) {
+        avctx->sample_rate = s->sample_rate;
+        avctx->bit_rate    = s->bit_rate;
+    }
+
+    /* channel config */
+    if (!err || (s->channels && s->out_channels != s->channels)) {
+        s->out_channels = s->channels;
+        s->output_mode  = s->channel_mode;
+        if (s->lfe_on)
+            s->output_mode |= AC3_OUTPUT_LFEON;
+        if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
+                avctx->request_channels < s->channels) {
+            s->out_channels = avctx->request_channels;
+            s->output_mode  = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
+            s->channel_layout = avpriv_ac3_channel_layout_tab[s->output_mode];
+        }
+        avctx->channels       = s->out_channels;
+        avctx->channel_layout = s->channel_layout;
+
+        s->loro_center_mix_level   = gain_levels[s->  center_mix_level];
+        s->loro_surround_mix_level = gain_levels[s->surround_mix_level];
+        s->ltrt_center_mix_level   = LEVEL_MINUS_3DB;
+        s->ltrt_surround_mix_level = LEVEL_MINUS_3DB;
+        /* set downmixing coefficients if needed */
+        if (s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
+                s->fbw_channels == s->out_channels)) {
+            set_downmix_coeffs(s);
+        }
+    } else if (!s->channels) {
+        av_log(avctx, AV_LOG_ERROR, "unable to determine channel mode\n");
+        return AVERROR_INVALIDDATA;
+    }
+    avctx->channels = s->out_channels;
+
+    /* set audio service type based on bitstream mode for AC-3 */
+    avctx->audio_service_type = s->bitstream_mode;
+    if (s->bitstream_mode == 0x7 && s->channels > 1)
+        avctx->audio_service_type = AV_AUDIO_SERVICE_TYPE_KARAOKE;
+
+    /* get output buffer */
+    frame->nb_samples = s->num_blocks * 256;
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
+    /* decode the audio blocks */
+    channel_map = ff_ac3_dec_channel_map[s->output_mode & ~AC3_OUTPUT_LFEON][s->lfe_on];
+    for (ch = 0; ch < AC3_MAX_CHANNELS; ch++) {
+        output[ch] = s->output[ch];
+        s->outptr[ch] = s->output[ch];
+    }
+    for (ch = 0; ch < s->channels; ch++) {
+        if (ch < s->out_channels)
+            s->outptr[channel_map[ch]] = (float *)frame->data[ch];
+    }
+    for (blk = 0; blk < s->num_blocks; blk++) {
+        if (!err && decode_audio_block(s, blk)) {
+            av_log(avctx, AV_LOG_ERROR, "error decoding the audio block\n");
+            err = 1;
+        }
+        if (err)
+            for (ch = 0; ch < s->out_channels; ch++)
+                memcpy(((float*)frame->data[ch]) + AC3_BLOCK_SIZE*blk, output[ch], 1024);
+        for (ch = 0; ch < s->out_channels; ch++)
+            output[ch] = s->outptr[channel_map[ch]];
+        for (ch = 0; ch < s->out_channels; ch++) {
+            if (!ch || channel_map[ch])
+                s->outptr[channel_map[ch]] += AC3_BLOCK_SIZE;
+        }
+    }
+
+    av_frame_set_decode_error_flags(frame, err ? FF_DECODE_ERROR_INVALID_BITSTREAM : 0);
+
+    /* keep last block for error concealment in next frame */
+    for (ch = 0; ch < s->out_channels; ch++)
+        memcpy(s->output[ch], output[ch], 1024);
+
+    *got_frame_ptr = 1;
+
+    return FFMIN(buf_size, s->frame_size);
+}
+
+/**
+ * Uninitialize the AC-3 decoder.
+ */
+static av_cold int ac3_decode_end(AVCodecContext *avctx)
+{
+    AC3DecodeContext *s = avctx->priv_data;
+    ff_mdct_end(&s->imdct_512);
+    ff_mdct_end(&s->imdct_256);
+
+    return 0;
+}
+
+#define OFFSET(x) offsetof(AC3DecodeContext, x)
+#define PAR (AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_AUDIO_PARAM)
+static const AVOption options[] = {
+    { "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 1.0, PAR },
+
+{"dmix_mode", "Preferred Stereo Downmix Mode", OFFSET(preferred_stereo_downmix), AV_OPT_TYPE_INT, {.i64 = -1 }, -1, 2, 0, "dmix_mode"},
+{"ltrt_cmixlev",   "Lt/Rt Center Mix Level",   OFFSET(ltrt_center_mix_level),    AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
+{"ltrt_surmixlev", "Lt/Rt Surround Mix Level", OFFSET(ltrt_surround_mix_level),  AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
+{"loro_cmixlev",   "Lo/Ro Center Mix Level",   OFFSET(loro_center_mix_level),    AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
+{"loro_surmixlev", "Lo/Ro Surround Mix Level", OFFSET(loro_surround_mix_level),  AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
+
+    { NULL},
+};
+
+static const AVClass ac3_decoder_class = {
+    .class_name = "AC3 decoder",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVCodec ff_ac3_decoder = {
+    .name           = "ac3",
+    .type           = AVMEDIA_TYPE_AUDIO,
+    .id             = AV_CODEC_ID_AC3,
+    .priv_data_size = sizeof (AC3DecodeContext),
+    .init           = ac3_decode_init,
+    .close          = ac3_decode_end,
+    .decode         = ac3_decode_frame,
+    .capabilities   = CODEC_CAP_DR1,
+    .long_name      = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
+    .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
+                                                      AV_SAMPLE_FMT_NONE },
+    .priv_class     = &ac3_decoder_class,
+};
+
+#if CONFIG_EAC3_DECODER
+static const AVClass eac3_decoder_class = {
+    .class_name = "E-AC3 decoder",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVCodec ff_eac3_decoder = {
+    .name           = "eac3",
+    .type           = AVMEDIA_TYPE_AUDIO,
+    .id             = AV_CODEC_ID_EAC3,
+    .priv_data_size = sizeof (AC3DecodeContext),
+    .init           = ac3_decode_init,
+    .close          = ac3_decode_end,
+    .decode         = ac3_decode_frame,
+    .capabilities   = CODEC_CAP_DR1,
+    .long_name      = NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),
+    .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
+                                                      AV_SAMPLE_FMT_NONE },
+    .priv_class     = &eac3_decoder_class,
+};
+#endif