int avpriv_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf,

                                 int bit_size, int sync_extension)

{

    GetBitContext gb;

    int specific_config_bitindex;



    if(bit_size<=0)

        return AVERROR_INVALIDDATA;



    init_get_bits(&gb, buf, bit_size);

    c->object_type = get_object_type(&gb);

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

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

    if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))

        c->channels = ff_mpeg4audio_channels[c->chan_config];

    c->sbr = -1;

    c->ps  = -1;

    if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&

        // check for W6132 Annex YYYY draft MP3onMP4

        !(show_bits(&gb, 3) & 0x03 && !(show_bits(&gb, 9) & 0x3F)))) {

        if (c->object_type == AOT_PS)

            c->ps = 1;

        c->ext_object_type = AOT_SBR;

        c->sbr = 1;

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

        c->object_type = get_object_type(&gb);

        if (c->object_type == AOT_ER_BSAC)

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

    } else {

        c->ext_object_type = AOT_NULL;

        c->ext_sample_rate = 0;

    }

    specific_config_bitindex = get_bits_count(&gb);



    if (c->object_type == AOT_ALS) {

        skip_bits(&gb, 5);

        if (show_bits_long(&gb, 24) != MKBETAG('\0','A','L','S'))

            skip_bits_long(&gb, 24);



        specific_config_bitindex = get_bits_count(&gb);



        if (parse_config_ALS(&gb, c))

            return -1;

    }



    if (c->ext_object_type != AOT_SBR && sync_extension) {

        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);

                    if (c->ext_sample_rate == c->sample_rate)

                        c->sbr = -1;

                }

                if (get_bits_left(&gb) > 11 && get_bits(&gb, 11) == 0x548)

                    c->ps = get_bits1(&gb);

                break;

            } else

                get_bits1(&gb); // skip 1 bit

        }

    }



    //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;



    return specific_config_bitindex;

}
