mpeg4audio.c 6.02 KB
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/*
 * MPEG-4 Audio common code
 * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>
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 * Copyright (c) 2009 Alex Converse <alex.converse@gmail.com>
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 *
 * 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
 */

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#include "get_bits.h"
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#include "put_bits.h"
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#include "mpeg4audio.h"

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/**
 * Parse MPEG-4 audio configuration for ALS object type.
 * @param[in] gb       bit reader context
 * @param[in] c        MPEG4AudioConfig structure to fill
 * @return on success 0 is returned, otherwise a value < 0
 */
static int parse_config_ALS(GetBitContext *gb, MPEG4AudioConfig *c)
{
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    if (get_bits_left(gb) < 112)
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        return AVERROR_INVALIDDATA;
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    if (get_bits_long(gb, 32) != MKBETAG('A','L','S','\0'))
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        return AVERROR_INVALIDDATA;
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    // override AudioSpecificConfig channel configuration and sample rate
    // which are buggy in old ALS conformance files
    c->sample_rate = get_bits_long(gb, 32);

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    if (c->sample_rate <= 0) {
        av_log(NULL, AV_LOG_ERROR, "Invalid sample rate %d\n", c->sample_rate);
        return AVERROR_INVALIDDATA;
    }

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    // skip number of samples
    skip_bits_long(gb, 32);

    // read number of channels
    c->chan_config = 0;
    c->channels    = get_bits(gb, 16) + 1;

    return 0;
}

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/* XXX: make sure to update the copies in the different encoders if you change
 * this table */
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const int avpriv_mpeg4audio_sample_rates[16] = {
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    96000, 88200, 64000, 48000, 44100, 32000,
    24000, 22050, 16000, 12000, 11025, 8000, 7350
};

const uint8_t ff_mpeg4audio_channels[8] = {
    0, 1, 2, 3, 4, 5, 6, 8
};

static inline int get_object_type(GetBitContext *gb)
{
    int object_type = get_bits(gb, 5);
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    if (object_type == AOT_ESCAPE)
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        object_type = 32 + get_bits(gb, 6);
    return object_type;
}

static inline int get_sample_rate(GetBitContext *gb, int *index)
{
    *index = get_bits(gb, 4);
    return *index == 0x0f ? get_bits(gb, 24) :
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        avpriv_mpeg4audio_sample_rates[*index];
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}

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int ff_mpeg4audio_get_config_gb(MPEG4AudioConfig *c, GetBitContext *gb,
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                                int sync_extension, void *logctx)
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{
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    int specific_config_bitindex, ret;
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    int start_bit_index = get_bits_count(gb);
    c->object_type = get_object_type(gb);
    c->sample_rate = get_sample_rate(gb, &c->sampling_index);
    c->chan_config = get_bits(gb, 4);
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    if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))
        c->channels = ff_mpeg4audio_channels[c->chan_config];
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    else {
        av_log(logctx, AV_LOG_ERROR, "Invalid chan_config %d\n", c->chan_config);
        return AVERROR_INVALIDDATA;
    }
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    c->sbr = -1;
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    c->ps  = -1;
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    if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&
        // check for W6132 Annex YYYY draft MP3onMP4
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        !(show_bits(gb, 3) & 0x03 && !(show_bits(gb, 9) & 0x3F)))) {
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        if (c->object_type == AOT_PS)
            c->ps = 1;
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        c->ext_object_type = AOT_SBR;
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        c->sbr = 1;
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        c->ext_sample_rate = get_sample_rate(gb, &c->ext_sampling_index);
        c->object_type = get_object_type(gb);
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        if (c->object_type == AOT_ER_BSAC)
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            c->ext_chan_config = get_bits(gb, 4);
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    } else {
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        c->ext_object_type = AOT_NULL;
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        c->ext_sample_rate = 0;
    }
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    specific_config_bitindex = get_bits_count(gb);
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    if (c->object_type == AOT_ALS) {
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        skip_bits(gb, 5);
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        if (show_bits(gb, 24) != MKBETAG('\0','A','L','S'))
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            skip_bits(gb, 24);
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        specific_config_bitindex = get_bits_count(gb);
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        ret = parse_config_ALS(gb, c);
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        if (ret < 0)
            return ret;
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    }

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    if (c->ext_object_type != AOT_SBR && sync_extension) {
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        while (get_bits_left(gb) > 15) {
            if (show_bits(gb, 11) == 0x2b7) { // sync extension
                get_bits(gb, 11);
                c->ext_object_type = get_object_type(gb);
                if (c->ext_object_type == AOT_SBR && (c->sbr = get_bits1(gb)) == 1) {
                    c->ext_sample_rate = get_sample_rate(gb, &c->ext_sampling_index);
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                    if (c->ext_sample_rate == c->sample_rate)
                        c->sbr = -1;
                }
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                if (get_bits_left(gb) > 11 && get_bits(gb, 11) == 0x548)
                    c->ps = get_bits1(gb);
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                break;
            } else
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                get_bits1(gb); // skip 1 bit
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        }
    }
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    //PS requires SBR
    if (!c->sbr)
        c->ps = 0;
    //Limit implicit PS to the HE-AACv2 Profile
    if ((c->ps == -1 && c->object_type != AOT_AAC_LC) || c->channels & ~0x01)
        c->ps = 0;

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    return specific_config_bitindex - start_bit_index;
}

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#if LIBAVCODEC_VERSION_MAJOR < 59
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int avpriv_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf,
                                 int bit_size, int sync_extension)
{
    GetBitContext gb;
    int ret;

    if (bit_size <= 0)
        return AVERROR_INVALIDDATA;

    ret = init_get_bits(&gb, buf, bit_size);
    if (ret < 0)
        return ret;

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    return ff_mpeg4audio_get_config_gb(c, &gb, sync_extension, NULL);
}
#endif

int avpriv_mpeg4audio_get_config2(MPEG4AudioConfig *c, const uint8_t *buf,
                                  int size, int sync_extension, void *logctx)
{
    GetBitContext gb;
    int ret;

    if (size <= 0)
        return AVERROR_INVALIDDATA;

    ret = init_get_bits8(&gb, buf, size);
    if (ret < 0)
        return ret;

    return ff_mpeg4audio_get_config_gb(c, &gb, sync_extension, logctx);
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}