ac3dec.c

/*
 * 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/channel_layout.h"
#include "libavutil/crc.h"
#include "libavutil/downmix_info.h"
#include "libavutil/opt.h"
#include "bswapdsp.h"
#include "internal.h"
#include "aac_ac3_parser.h"
#include "ac3_parser_internal.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
};

#if (!USE_FIXED)
/** dynamic range table. converts codes to scale factors. */
static float dynamic_range_tab[256];
float ff_ac3_heavy_dynamic_range_tab[256];
#endif

/** 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
};

/** Adjustments in dB gain (LFE, +10 to -21 dB) */
static const float gain_levels_lfe[32] = {
    3.162275, 2.818382, 2.511886, 2.238719, 1.995261, 1.778278, 1.584893,
    1.412536, 1.258924, 1.122018, 1.000000, 0.891251, 0.794328, 0.707946,
    0.630957, 0.562341, 0.501187, 0.446683, 0.398107, 0.354813, 0.316227,
    0.281838, 0.251188, 0.223872, 0.199526, 0.177828, 0.158489, 0.141253,
    0.125892, 0.112201, 0.100000, 0.089125
};

/**
 * 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)) * (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);
    }

#if (!USE_FIXED)
    /* 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 compr dynamic range table
       reference: Section 7.7.2 Heavy Compression */
    for (i = 0; i < 256; i++) {
        int v = (i >> 4) - ((i >> 7) << 4) - 4;
        ff_ac3_heavy_dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0xF) | 0x10);
    }
#endif
}

/**
 * AVCodec initialization
 */
static av_cold int ac3_decode_init(AVCodecContext *avctx)
{
    AC3DecodeContext *s = avctx->priv_data;
    int i;

    s->avctx = avctx;

    ac3_tables_init();
    ff_mdct_init(&s->imdct_256, 8, 1, 1.0);
    ff_mdct_init(&s->imdct_512, 9, 1, 1.0);
    AC3_RENAME(ff_kbd_window_init)(s->window, 5.0, 256);
    ff_bswapdsp_init(&s->bdsp);

#if (USE_FIXED)
    s->fdsp = avpriv_alloc_fixed_dsp(avctx->flags & AV_CODEC_FLAG_BITEXACT);
#else
    s->fdsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);