Update internal FFmpeg copy.

1 files changed, 1173 insertions, 0 deletions

diff --git a/contrib/ffmpeg/libavcodec/ac3dec.c b/contrib/ffmpeg/libavcodec/ac3dec.c
new file mode 100644
index 000000000..0ce75e769
--- /dev/null
+++ b/contrib/ffmpeg/libavcodec/ac3dec.c
@@ -0,0 +1,1173 @@
+/*
+ * AC-3 Audio Decoder
+ * This code is developed as part of Google Summer of Code 2006 Program.
+ *
+ * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
+ * Copyright (c) 2007 Justin Ruggles
+ *
+ * Portions of this code are derived from liba52
+ * http://liba52.sourceforge.net
+ * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
+ * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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 "avcodec.h"
+#include "ac3_parser.h"
+#include "bitstream.h"
+#include "crc.h"
+#include "dsputil.h"
+#include "random.h"
+
+/**
+ * Table of bin locations for rematrixing bands
+ * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
+ */
+static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
+
+/**
+ * table for exponent to scale_factor mapping
+ * scale_factors[i] = 2 ^ -i
+ */
+static float scale_factors[25];
+
+/** table for grouping exponents */
+static uint8_t exp_ungroup_tab[128][3];
+
+
+/** tables for ungrouping mantissas */
+static float b1_mantissas[32][3];
+static float b2_mantissas[128][3];
+static float b3_mantissas[8];
+static float b4_mantissas[128][2];
+static float 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 */
+#define LEVEL_MINUS_3DB         0.7071067811865476
+#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
+#define LEVEL_MINUS_6DB         0.5000000000000000
+#define LEVEL_MINUS_9DB         0.3535533905932738
+#define LEVEL_ZERO              0.0000000000000000
+#define LEVEL_ONE               1.0000000000000000
+
+static const float gain_levels[6] = {
+    LEVEL_ZERO,
+    LEVEL_ONE,
+    LEVEL_MINUS_3DB,
+    LEVEL_MINUS_4POINT5DB,
+    LEVEL_MINUS_6DB,
+    LEVEL_MINUS_9DB
+};
+
+/**
+ * Table for center mix levels
+ * reference: Section 5.4.2.4 cmixlev
+ */
+static const uint8_t center_levels[4] = { 2, 3, 4, 3 };
+
+/**
+ * Table for surround mix levels
+ * reference: Section 5.4.2.5 surmixlev
+ */
+static const uint8_t surround_levels[4] = { 2, 4, 0, 4 };
+
+/**
+ * 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] = {
+    { { 1, 0 }, { 0, 1 },                               },
+    { { 2, 2 },                                         },
+    { { 1, 0 }, { 0, 1 },                               },
+    { { 1, 0 }, { 3, 3 }, { 0, 1 },                     },
+    { { 1, 0 }, { 0, 1 }, { 4, 4 },                     },
+    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 },           },
+    { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 },           },
+    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
+};
+
+/* override ac3.h to include coupling channel */
+#undef AC3_MAX_CHANNELS
+#define AC3_MAX_CHANNELS 7
+#define CPL_CH 0
+
+#define AC3_OUTPUT_LFEON  8
+
+typedef struct {
+    int channel_mode;                       ///< channel mode (acmod)
+    int block_switch[AC3_MAX_CHANNELS];     ///< block switch flags
+    int dither_flag[AC3_MAX_CHANNELS];      ///< dither flags
+    int dither_all;                         ///< true if all channels are dithered
+    int cpl_in_use;                         ///< coupling in use
+    int channel_in_cpl[AC3_MAX_CHANNELS];   ///< channel in coupling
+    int phase_flags_in_use;                 ///< phase flags in use
+    int phase_flags[18];                    ///< phase flags
+    int cpl_band_struct[18];                ///< coupling band structure
+    int num_rematrixing_bands;              ///< number of rematrixing bands
+    int rematrixing_flags[4];               ///< rematrixing flags
+    int exp_strategy[AC3_MAX_CHANNELS];     ///< exponent strategies
+    int snr_offset[AC3_MAX_CHANNELS];       ///< signal-to-noise ratio offsets
+    int fast_gain[AC3_MAX_CHANNELS];        ///< fast gain values (signal-to-mask ratio)
+    int dba_mode[AC3_MAX_CHANNELS];         ///< delta bit allocation mode
+    int dba_nsegs[AC3_MAX_CHANNELS];        ///< number of delta segments
+    uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
+    uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
+    uint8_t dba_values[AC3_MAX_CHANNELS][8];  ///< delta values for each segment
+
+    int sample_rate;                        ///< sample frequency, in Hz
+    int bit_rate;                           ///< stream bit rate, in bits-per-second
+    int frame_size;                         ///< current frame size, in bytes
+
+    int channels;                           ///< number of total channels
+    int fbw_channels;                       ///< number of full-bandwidth channels
+    int lfe_on;                             ///< lfe channel in use
+    int lfe_ch;                             ///< index of LFE channel
+    int output_mode;                        ///< output channel configuration
+    int out_channels;                       ///< number of output channels
+
+    int center_mix_level;                   ///< Center mix level index
+    int surround_mix_level;                 ///< Surround mix level index
+    float downmix_coeffs[AC3_MAX_CHANNELS][2];  ///< stereo downmix coefficients
+    float dynamic_range[2];                 ///< dynamic range
+    float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
+    int   num_cpl_bands;                    ///< number of coupling bands
+    int   num_cpl_subbands;                 ///< number of coupling sub bands
+    int   start_freq[AC3_MAX_CHANNELS];     ///< start frequency bin
+    int   end_freq[AC3_MAX_CHANNELS];       ///< end frequency bin
+    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
+
+    int8_t  dexps[AC3_MAX_CHANNELS][256];   ///< decoded exponents
+    uint8_t bap[AC3_MAX_CHANNELS][256];     ///< bit allocation pointers
+    int16_t psd[AC3_MAX_CHANNELS][256];     ///< scaled exponents
+    int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
+    int16_t mask[AC3_MAX_CHANNELS][50];     ///< masking curve values
+
+    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  ///< transform coefficients
+
+    /* For IMDCT. */
+    MDCTContext imdct_512;                  ///< for 512 sample IMDCT
+    MDCTContext imdct_256;                  ///< for 256 sample IMDCT
+    DSPContext  dsp;                        ///< for optimization
+    float       add_bias;                   ///< offset for float_to_int16 conversion
+    float       mul_bias;                   ///< scaling for float_to_int16 conversion
+
+    DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]);     ///< output after imdct transform and windowing
+    DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
+    DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]);      ///< delay - added to the next block
+    DECLARE_ALIGNED_16(float, tmp_imdct[256]);                      ///< temporary storage for imdct transform
+    DECLARE_ALIGNED_16(float, tmp_output[512]);                     ///< temporary storage for output before windowing
+    DECLARE_ALIGNED_16(float, window[256]);                         ///< window coefficients
+
+    /* Miscellaneous. */
+    GetBitContext gbc;                      ///< bitstream reader
+    AVRandomState dith_state;               ///< for dither generation
+    AVCodecContext *avctx;                  ///< parent context
+} AC3DecodeContext;
+
+/**
+ * Symmetrical Dequantization
+ * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
+ *            Tables 7.19 to 7.23
+ */
+static inline float
+symmetric_dequant(int code, int levels)
+{
+    return (code - (levels >> 1)) * (2.0f / levels);
+}
+
+/*
+ * Initialize tables at runtime.
+ */
+static void ac3_tables_init(void)
+{
+    int i;
+
+    /* 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( i / 9     , 3);
+        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
+        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
+    }
+    for(i=0; i<128; i++) {
+        /* bap=2 mantissas */
+        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
+        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
+        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 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);
+    }
+
+    /* generate scale factors for exponents and asymmetrical dequantization
+       reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
+    for (i = 0; i < 25; i++)
+        scale_factors[i] = pow(2.0, -i);
+
+    /* generate exponent tables
+       reference: Section 7.1.3 Exponent Decoding */
+    for(i=0; i<128; i++) {
+        exp_ungroup_tab[i][0] =  i / 25;
+        exp_ungroup_tab[i][1] = (i % 25) / 5;
+        exp_ungroup_tab[i][2] = (i % 25) % 5;
+    }
+}
+
+
+/**
+ * AVCodec initialization
+ */
+static int ac3_decode_init(AVCodecContext *avctx)
+{
+    AC3DecodeContext *s = avctx->priv_data;
+    s->avctx = avctx;
+
+    ac3_common_init();
+    ac3_tables_init();
+    ff_mdct_init(&s->imdct_256, 8, 1);
+    ff_mdct_init(&s->imdct_512, 9, 1);
+    ff_kbd_window_init(s->window, 5.0, 256);
+    dsputil_init(&s->dsp, avctx);
+    av_init_random(0, &s->dith_state);
+
+    /* set bias values for float to int16 conversion */
+    if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
+        s->add_bias = 385.0f;
+        s->mul_bias = 1.0f;
+    } else {
+        s->add_bias = 0.0f;
+        s->mul_bias = 32767.0f;
+    }
+
+    /* 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;
+    }
+
+    return 0;
+}
+
+/**
+ * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
+ * GetBitContext within AC3DecodeContext must point to
+ * start of the synchronized ac3 bitstream.
+ */
+static int ac3_parse_header(AC3DecodeContext *s)
+{
+    AC3HeaderInfo hdr;
+    GetBitContext *gbc = &s->gbc;
+    int err, i;
+
+    err = ff_ac3_parse_header(gbc->buffer, &hdr);
+    if(err)
+        return err;
+
+    if(hdr.bitstream_id > 10)
+        return AC3_PARSE_ERROR_BSID;
+
+    /* get decoding parameters from header info */
+    s->bit_alloc_params.sr_code     = hdr.sr_code;
+    s->channel_mode                 = hdr.channel_mode;
+    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;
+
+    /* set default output to all source channels */
+    s->out_channels = s->channels;
+    s->output_mode = s->channel_mode;
+    if(s->lfe_on)
+        s->output_mode |= AC3_OUTPUT_LFEON;
+
+    /* set default mix levels */
+    s->center_mix_level   = 3;  // -4.5dB
+    s->surround_mix_level = 4;  // -6.0dB
+
+    /* skip over portion of header which has already been read */
+    skip_bits(gbc, 16); // skip the sync_word
+    skip_bits(gbc, 16); // skip crc1
+    skip_bits(gbc, 8);  // skip fscod and frmsizecod
+    skip_bits(gbc, 11); // skip bsid, bsmod, and acmod
+    if(s->channel_mode == AC3_CHMODE_STEREO) {
+        skip_bits(gbc, 2); // skip dsurmod
+    } else {
+        if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
+            s->center_mix_level = center_levels[get_bits(gbc, 2)];
+        if(s->channel_mode & 4)
+            s->surround_mix_level = surround_levels[get_bits(gbc, 2)];
+    }
+    skip_bits1(gbc); // skip lfeon
+
+    /* 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;
+}
+
+/**
+ * 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];
+
+    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;
+    }
+}
+
+/**
+ * Decode the grouped exponents according to exponent strategy.
+ * reference: Section 7.1.3 Exponent Decoding
+ */
+static void 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++] = exp_ungroup_tab[expacc][0];
+        dexp[i++] = exp_ungroup_tab[expacc][1];
+        dexp[i++] = exp_ungroup_tab[expacc][2];
+    }
+
+    /* convert to absolute exps and expand groups */
+    prevexp = absexp;
+    for(i=0; i<ngrps*3; i++) {
+        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
+        for(j=0; j<group_size; j++) {
+            dexps[(i*group_size)+j] = prevexp;
+        }
+    }
+}
+
+/**
+ * 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 uncouple_channels(AC3DecodeContext *s)
+{
+    int i, j, ch, bnd, subbnd;
+
+    subbnd = -1;
+    i = s->start_freq[CPL_CH];
+    for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
+        do {
+            subbnd++;
+            for(j=0; j<12; j++) {
+                for(ch=1; ch<=s->fbw_channels; ch++) {
+                    if(s->channel_in_cpl[ch]) {
+                        s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f;
+                        if (ch == 2 && s->phase_flags[bnd])
+                            s->transform_coeffs[ch][i] = -s->transform_coeffs[ch][i];
+                    }
+                }
+                i++;
+            }
+        } while(s->cpl_band_struct[subbnd]);
+    }
+}
+
+/**
+ * Grouped mantissas for 3-level 5-level and 11-level quantization
+ */
+typedef struct {
+    float b1_mant[3];
+    float b2_mant[3];
+    float b4_mant[2];
+    int b1ptr;
+    int b2ptr;
+    int b4ptr;
+} mant_groups;
+
+/**
+ * Get the transform coefficients for a particular channel
+ * reference: Section 7.3 Quantization and Decoding of Mantissas
+ */
+static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
+{
+    GetBitContext *gbc = &s->gbc;
+    int i, gcode, tbap, start, end;
+    uint8_t *exps;
+    uint8_t *bap;
+    float *coeffs;
+
+    exps = s->dexps[ch_index];
+    bap = s->bap[ch_index];
+    coeffs = s->transform_coeffs[ch_index];
+    start = s->start_freq[ch_index];
+    end = s->end_freq[ch_index];
+
+    for (i = start; i < end; i++) {
+        tbap = bap[i];
+        switch (tbap) {
+            case 0:
+                coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f;
+                break;
+
+            case 1:
+                if(m->b1ptr > 2) {
+                    gcode = get_bits(gbc, 5);
+                    m->b1_mant[0] = b1_mantissas[gcode][0];
+                    m->b1_mant[1] = b1_mantissas[gcode][1];
+                    m->b1_mant[2] = b1_mantissas[gcode][2];
+                    m->b1ptr = 0;
+                }
+                coeffs[i] = m->b1_mant[m->b1ptr++];
+                break;
+
+            case 2:
+                if(m->b2ptr > 2) {
+                    gcode = get_bits(gbc, 7);
+                    m->b2_mant[0] = b2_mantissas[gcode][0];
+                    m->b2_mant[1] = b2_mantissas[gcode][1];
+                    m->b2_mant[2] = b2_mantissas[gcode][2];
+                    m->b2ptr = 0;
+                }
+                coeffs[i] = m->b2_mant[m->b2ptr++];
+                break;
+
+            case 3:
+                coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
+                break;
+
+            case 4:
+                if(m->b4ptr > 1) {
+                    gcode = get_bits(gbc, 7);
+                    m->b4_mant[0] = b4_mantissas[gcode][0];
+                    m->b4_mant[1] = b4_mantissas[gcode][1];
+                    m->b4ptr = 0;
+                }
+                coeffs[i] = m->b4_mant[m->b4ptr++];
+                break;
+
+            case 5:
+                coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
+                break;
+
+            default:
+                /* asymmetric dequantization */
+                coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1];
+                break;
+        }
+        coeffs[i] *= scale_factors[exps[i]];
+    }
+
+    return 0;
+}
+
+/**
+ * Remove random dithering from coefficients with zero-bit mantissas
+ * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
+ */
+static void remove_dithering(AC3DecodeContext *s) {
+    int ch, i;
+    int end=0;
+    float *coeffs;
+    uint8_t *bap;
+
+    for(ch=1; ch<=s->fbw_channels; ch++) {
+        if(!s->dither_flag[ch]) {
+            coeffs = s->transform_coeffs[ch];
+            bap = s->bap[ch];
+            if(s->channel_in_cpl[ch])
+                end = s->start_freq[CPL_CH];
+            else
+                end = s->end_freq[ch];
+            for(i=0; i<end; i++) {
+                if(!bap[i])
+                    coeffs[i] = 0.0f;
+            }
+            if(s->channel_in_cpl[ch]) {
+                bap = s->bap[CPL_CH];
+                for(; i<s->end_freq[CPL_CH]; i++) {
+                    if(!bap[i])
+                        coeffs[i] = 0.0f;
+                }
+            }
+        }
+    }
+}
+
+/**
+ * Get the transform coefficients.
+ */
+static int get_transform_coeffs(AC3DecodeContext *s)
+{
+    int ch, end;
+    int got_cplchan = 0;
+    mant_groups m;
+
+    m.b1ptr = m.b2ptr = m.b4ptr = 3;
+
+    for (ch = 1; ch <= s->channels; ch++) {
+        /* transform coefficients for full-bandwidth channel */
+        if (get_transform_coeffs_ch(s, ch, &m))
+            return -1;
+        /* tranform coefficients for coupling channel come right after the
+           coefficients for the first coupled channel*/
+        if (s->channel_in_cpl[ch])  {
+            if (!got_cplchan) {
+                if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
+                    av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
+                    return -1;
+                }
+                uncouple_channels(s);
+                got_cplchan = 1;
+            }
+            end = s->end_freq[CPL_CH];
+        } else {
+            end = s->end_freq[ch];
+        }
+        do
+            s->transform_coeffs[ch][end] = 0;
+        while(++end < 256);
+    }
+
+    /* if any channel doesn't use dithering, zero appropriate coefficients */
+    if(!s->dither_all)
+        remove_dithering(s);
+
+    return 0;
+}
+
+/**
+ * Stereo rematrixing.
+ * reference: Section 7.5.4 Rematrixing : Decoding Technique
+ */
+static void do_rematrixing(AC3DecodeContext *s)
+{
+    int bnd, i;
+    int end, bndend;
+    float tmp0, tmp1;
+
+    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, rematrix_band_tab[bnd+1]);
+            for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
+                tmp0 = s->transform_coeffs[1][i];
+                tmp1 = s->transform_coeffs[2][i];
+                s->transform_coeffs[1][i] = tmp0 + tmp1;
+                s->transform_coeffs[2][i] = tmp0 - tmp1;
+            }
+        }
+    }
+}
+
+/**
+ * Perform the 256-point IMDCT
+ */
+static void do_imdct_256(AC3DecodeContext *s, int chindex)
+{
+    int i, k;
+    DECLARE_ALIGNED_16(float, x[128]);
+    FFTComplex z[2][64];
+    float *o_ptr = s->tmp_output;
+
+    for(i=0; i<2; i++) {
+        /* de-interleave coefficients */
+        for(k=0; k<128; k++) {
+            x[k] = s->transform_coeffs[chindex][2*k+i];
+        }
+
+        /* run standard IMDCT */
+        s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
+
+        /* reverse the post-rotation & reordering from standard IMDCT */
+        for(k=0; k<32; k++) {
+            z[i][32+k].re = -o_ptr[128+2*k];
+            z[i][32+k].im = -o_ptr[2*k];
+            z[i][31-k].re =  o_ptr[2*k+1];
+            z[i][31-k].im =  o_ptr[128+2*k+1];
+        }
+    }
+
+    /* apply AC-3 post-rotation & reordering */
+    for(k=0; k<64; k++) {
+        o_ptr[    2*k  ] = -z[0][   k].im;
+        o_ptr[    2*k+1] =  z[0][63-k].re;
+        o_ptr[128+2*k  ] = -z[0][   k].re;
+        o_ptr[128+2*k+1] =  z[0][63-k].im;
+        o_ptr[256+2*k  ] = -z[1][   k].re;
+        o_ptr[256+2*k+1] =  z[1][63-k].im;
+        o_ptr[384+2*k  ] =  z[1][   k].im;
+        o_ptr[384+2*k+1] = -z[1][63-k].re;
+    }
+}
+
+/**
+ * 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 ch;
+    int channels;
+
+    /* Don't perform the IMDCT on the LFE channel unless it's used in the output */
+    channels = s->fbw_channels;
+    if(s->output_mode & AC3_OUTPUT_LFEON)
+        channels++;
+
+    for (ch=1; ch<=channels; ch++) {
+        if (s->block_switch[ch]) {
+            do_imdct_256(s, ch);
+        } else {
+            s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
+                                        s->transform_coeffs[ch], s->tmp_imdct);
+        }
+        /* For the first half of the block, apply the window, add the delay
+           from the previous block, and send to output */
+        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
+                                     s->window, s->delay[ch-1], 0, 256, 1);
+        /* For the second half of the block, apply the window and store the
+           samples to delay, to be combined with the next block */
+        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
+                                   s->window, 256);
+    }
+}
+
+/**
+ * Downmix the output to mono or stereo.
+ */
+static void ac3_downmix(AC3DecodeContext *s)
+{
+    int i, j;
+    float v0, v1, s0, s1;
+
+    for(i=0; i<256; i++) {
+        v0 = v1 = s0 = s1 = 0.0f;
+        for(j=0; j<s->fbw_channels; j++) {
+            v0 += s->output[j][i] * s->downmix_coeffs[j][0];
+            v1 += s->output[j][i] * s->downmix_coeffs[j][1];
+            s0 += s->downmix_coeffs[j][0];
+            s1 += s->downmix_coeffs[j][1];
+        }
+        v0 /= s0;
+        v1 /= s1;
+        if(s->output_mode == AC3_CHMODE_MONO) {
+            s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
+        } else if(s->output_mode == AC3_CHMODE_STEREO) {
+            s->output[0][i] = v0;
+            s->output[1][i] = v1;
+        }
+    }
+}
+
+/**
+ * Parse an audio block from AC-3 bitstream.
+ */
+static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
+{
+    int fbw_channels = s->fbw_channels;
+    int channel_mode = s->channel_mode;
+    int i, bnd, seg, ch;
+    GetBitContext *gbc = &s->gbc;
+    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
+
+    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
+
+    /* block switch flags */
+    for (ch = 1; ch <= fbw_channels; ch++)
+        s->block_switch[ch] = get_bits1(gbc);
+
+    /* dithering flags */
+    s->dither_all = 1;
+    for (ch = 1; ch <= fbw_channels; ch++) {
+        s->dither_flag[ch] = get_bits1(gbc);
+        if(!s->dither_flag[ch])
+            s->dither_all = 0;
+    }
+
+    /* 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->avctx->drc_scale)+1.0;
+        } else if(blk == 0) {
+            s->dynamic_range[i] = 1.0f;
+        }
+    } while(i--);
+
+    /* coupling strategy */
+    if (get_bits1(gbc)) {
+        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
+        s->cpl_in_use = get_bits1(gbc);
+        if (s->cpl_in_use) {
+            /* coupling in use */
+            int cpl_begin_freq, cpl_end_freq;
+
+            /* determine which channels are coupled */
+            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 and band structure */
+            cpl_begin_freq = get_bits(gbc, 4);
+            cpl_end_freq = get_bits(gbc, 4);
+            if (3 + cpl_end_freq - cpl_begin_freq < 0) {
+                av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
+                return -1;
+            }
+            s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
+            s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
+            s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
+            for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
+                if (get_bits1(gbc)) {
+                    s->cpl_band_struct[bnd] = 1;
+                    s->num_cpl_bands--;
+                }
+            }
+            s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
+        } else {
+            /* coupling not in use */
+            for (ch = 1; ch <= fbw_channels; ch++)
+                s->channel_in_cpl[ch] = 0;
+        }
+    }
+
+    /* coupling coordinates */
+    if (s->cpl_in_use) {
+        int cpl_coords_exist = 0;
+
+        for (ch = 1; ch <= fbw_channels; ch++) {
+            if (s->channel_in_cpl[ch]) {
+                if (get_bits1(gbc)) {
+                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
+                    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 / 16.0f;
+                        else
+                            s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f;
+                        s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord];
+                    }
+                }
+            }
+        }
+        /* 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 (get_bits1(gbc)) {
+            s->num_rematrixing_bands = 4;
+            if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
+                s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
+            for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
+                s->rematrixing_flags[bnd] = get_bits1(gbc);
+        }
+    }
+
+    /* exponent strategies for each channel */
+    s->exp_strategy[CPL_CH] = EXP_REUSE;
+    s->exp_strategy[s->lfe_ch] = EXP_REUSE;
+    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
+        if(ch == s->lfe_ch)
+            s->exp_strategy[ch] = get_bits(gbc, 1);
+        else
+            s->exp_strategy[ch] = get_bits(gbc, 2);
+        if(s->exp_strategy[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[ch] != EXP_REUSE) {
+            int prev = s->end_freq[ch];
+            if (s->channel_in_cpl[ch])
+                s->end_freq[ch] = s->start_freq[CPL_CH];
+            else {
+                int bandwidth_code = get_bits(gbc, 6);
+                if (bandwidth_code > 60) {
+                    av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
+                    return -1;
+                }
+                s->end_freq[ch] = bandwidth_code * 3 + 73;
+            }
+            if(blk > 0 && s->end_freq[ch] != prev)
+                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
+        }
+    }
+    s->start_freq[s->lfe_ch] = 0;
+    s->end_freq[s->lfe_ch] = 7;
+
+    /* decode exponents for each channel */
+    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
+        if (s->exp_strategy[ch] != EXP_REUSE) {
+            int group_size, num_groups;
+            group_size = 3 << (s->exp_strategy[ch] - 1);
+            if(ch == CPL_CH)
+                num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
+            else if(ch == s->lfe_ch)
+                num_groups = 2;
+            else
+                num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
+            s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
+            decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
+                             &s->dexps[ch][s->start_freq[ch]+!!ch]);
+            if(ch != CPL_CH && ch != s->lfe_ch)
+                skip_bits(gbc, 2); /* skip gainrng */
+        }
+    }
+
+    /* bit allocation information */
+    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=!s->cpl_in_use; ch<=s->channels; ch++) {
+            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
+        }
+    }
+
+    /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
+    if (get_bits1(gbc)) {
+        int csnr;
+        csnr = (get_bits(gbc, 6) - 15) << 4;
+        for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
+            s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
+            s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
+        }
+        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
+    }
+
+    /* coupling leak information */
+    if (s->cpl_in_use && get_bits1(gbc)) {
+        s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
+        s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
+        bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
+    }
+
+    /* delta bit allocation information */
+    if (get_bits1(gbc)) {
+        /* delta bit allocation exists (strategy) */
+        for (ch = !s->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 = !s->cpl_in_use; ch <= fbw_channels; ch++) {
+            if (s->dba_mode[ch] == DBA_NEW) {
+                s->dba_nsegs[ch] = get_bits(gbc, 3);
+                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);
+                }
+            }
+        }
+    } else if(blk == 0) {
+        for(ch=0; ch<=s->channels; ch++) {
+            s->dba_mode[ch] = DBA_NONE;
+        }
+    }
+
+    /* Bit allocation */
+    for(ch=!s->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 */
+            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]);
+        }
+        if(bit_alloc_stages[ch] > 0) {
+            /* Compute bit allocation */
+            ff_ac3_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,
+                                      s->bap[ch]);
+        }
+    }
+
+    /* unused dummy data */
+    if (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. */
+    if (get_transform_coeffs(s)) {
+        av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
+        return -1;
+    }
+
+    /* 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 = 2.0f * s->mul_bias;
+        if(s->channel_mode == AC3_CHMODE_DUALMONO) {
+            gain *= s->dynamic_range[ch-1];
+        } else {
+            gain *= s->dynamic_range[0];
+        }
+        for(i=0; i<s->end_freq[ch]; i++) {
+            s->transform_coeffs[ch][i] *= gain;
+        }
+    }
+
+    do_imdct(s);
+
+    /* downmix output if needed */
+    if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
+            s->fbw_channels == s->out_channels)) {
+        ac3_downmix(s);
+    }
+
+    /* convert float to 16-bit integer */
+    for(ch=0; ch<s->out_channels; ch++) {
+        for(i=0; i<256; i++) {
+            s->output[ch][i] += s->add_bias;
+        }
+        s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
+    }
+
+    return 0;
+}
+
+/**
+ * Decode a single AC-3 frame.
+ */
+static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
+{
+    AC3DecodeContext *s = avctx->priv_data;
+    int16_t *out_samples = (int16_t *)data;
+    int i, blk, ch, err;
+
+    /* initialize the GetBitContext with the start of valid AC-3 Frame */
+    init_get_bits(&s->gbc, buf, buf_size * 8);
+
+    /* parse the syncinfo */
+    err = ac3_parse_header(s);
+    if(err) {
+        switch(err) {
+            case AC3_PARSE_ERROR_SYNC:
+                av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
+                break;
+            case AC3_PARSE_ERROR_BSID:
+                av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
+                break;
+            case AC3_PARSE_ERROR_SAMPLE_RATE:
+                av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
+                break;
+            case AC3_PARSE_ERROR_FRAME_SIZE:
+                av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
+                break;
+            default:
+                av_log(avctx, AV_LOG_ERROR, "invalid header\n");
+                break;
+        }
+        return -1;
+    }
+
+    /* check that reported frame size fits in input buffer */
+    if(s->frame_size > buf_size) {
+        av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
+        return -1;
+    }
+
+    /* check for crc mismatch */
+    if(avctx->error_resilience >= FF_ER_CAREFUL) {
+        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");
+            return -1;
+        }
+        /* TODO: error concealment */
+    }
+
+    avctx->sample_rate = s->sample_rate;
+    avctx->bit_rate = s->bit_rate;
+
+    /* channel config */
+    s->out_channels = s->channels;
+    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;
+    }
+    avctx->channels = s->out_channels;
+
+    /* 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);
+    }
+
+    /* parse the audio blocks */
+    for (blk = 0; blk < NB_BLOCKS; blk++) {
+        if (ac3_parse_audio_block(s, blk)) {
+            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
+            *data_size = 0;
+            return s->frame_size;
+        }
+        for (i = 0; i < 256; i++)
+            for (ch = 0; ch < s->out_channels; ch++)
+                *(out_samples++) = s->int_output[ch][i];
+    }
+    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
+    return s->frame_size;
+}
+
+/**
+ * Uninitialize the AC-3 decoder.
+ */
+static 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;
+}
+
+AVCodec ac3_decoder = {
+    .name = "ac3",
+    .type = CODEC_TYPE_AUDIO,
+    .id = CODEC_ID_AC3,
+    .priv_data_size = sizeof (AC3DecodeContext),
+    .init = ac3_decode_init,
+    .close = ac3_decode_end,
+    .decode = ac3_decode_frame,
+};