PeerStreamer

/*

 * MPEG-4 Audio common code

 * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>

 *

 * 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 "get_bits.h"

#include "mpeg4audio.h"

const int ff_mpeg4audio_sample_rates[16] = {

    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);

    if (object_type == 31)

        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) :

        ff_mpeg4audio_sample_rates[*index];

}

int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_size)

{

    GetBitContext gb;

    int specific_config_bitindex;

    init_get_bits(&gb, buf, buf_size*8);

    c->object_type = get_object_type(&gb);

    c->sample_rate = get_sample_rate(&gb, &c->sampling_index);

    c->chan_config = get_bits(&gb, 4);

    c->sbr = -1;

    if (c->object_type == 5) {

        c->ext_object_type = c->object_type;

        c->sbr = 1;

        c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);

        c->object_type = get_object_type(&gb);

    } else {

        c->ext_object_type = 0;

        c->ext_sample_rate = 0;

    }

    specific_config_bitindex = get_bits_count(&gb);

    if (c->ext_object_type != 5) {

        int bits_left = buf_size*8 - specific_config_bitindex;

        for (; bits_left > 15; bits_left--) {

            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 == 5 && (c->sbr = get_bits1(&gb)) == 1)

                    c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);

                break;

            } else

                get_bits1(&gb); // skip 1 bit

        }

    }

    return specific_config_bitindex;

}