ac3dec.c

ffmpeg移植到symbian的全部源代码

/*
 * 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 <[e-mail]>
 * Copyright (C) 1999-2000 Aaron Holtzman <[e-mail]>
 *
 * 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 "libavutil/crc.h"
#include "libavutil/random.h"
#include "avcodec.h"
#include "ac3_parser.h"
#include "bitstream.h"
#include "dsputil.h"
#include "ac3dec.h"
#include "ac3dec_data.h"

/** Maximum possible frame size when the specification limit is ignored */
#define AC3_MAX_FRAME_SIZE 21695

/** table for grouping exponents */
static uint8_t exp_ungroup_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 */
#define LEVEL_PLUS_3DB          1.4142135623730950
#define LEVEL_PLUS_1POINT5DB    1.1892071150027209
#define LEVEL_MINUS_1POINT5DB   0.8408964152537145
#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[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 center mix levels
 * reference: Section 5.4.2.4 cmixlev
 */
static const uint8_t center_levels[4] = { 4, 5, 6, 5 };

/**
 * Table for surround mix levels
 * reference: Section 5.4.2.5 surmixlev
 */
static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };

/**
 * 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 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 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 av_cold 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;
    }
    s->downmixed = 1;

    /* allocate context input buffer */
    if (avctx->error_resilience >= FF_ER_CAREFUL) {
        s->input_buffer = av_mallocz(AC3_MAX_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
        if (!s->input_buffer)
            return AVERROR_NOMEM;
    }

    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)
{
    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 AC3 or E-AC3 frame header
 */
static int parse_frame_header(AC3DecodeContext *s)
{
    AC3HeaderInfo hdr;
    GetBitContext *gbc = &s->gbc;
    int err;

    err = ff_ac3_parse_header(gbc, &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;
    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;
    }

    return ac3_parse_header(s);
}

/**
 * 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[center_levels[s->center_mix_level]];
    float smix = gain_levels[surround_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;
    }

    /* calculate adjustment needed for each channel to avoid clipping */
    s->downmix_coeff_adjust[0] = s->downmix_coeff_adjust[1] = 0.0f;
    for(i=0; i<s->fbw_channels; i++) {
        s->downmix_coeff_adjust[0] += s->downmix_coeffs[i][0];
        s->downmix_coeff_adjust[1] += s->downmix_coeffs[i][1];
    }
    s->downmix_coeff_adjust[0] = 1.0f / s->downmix_coeff_adjust[0];
    s->downmix_coeff_adjust[1] = 1.0f / s->downmix_coeff_adjust[1];
}

/**
 * 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->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
                        if (ch == 2 && s->phase_flags[bnd])
                            s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
                    }
                }
                i++;
            }
        } while(s->cpl_band_struct[subbnd]);
    }
}

/**
 * Grouped mantissas for 3-level 5-level and 11-level quantization
 */