static int aac_sync(uint64_t state, AACAC3ParseContext *hdr_info,
        int *need_next_header, int *new_frame_start)
{
    GetBitContext bits;
    int size, rdb, ch, sr;
    union {
        uint64_t u64;
        uint8_t  u8[8];
    } tmp;

    tmp.u64 = be2me_64(state);
    init_get_bits(&bits, tmp.u8+8-AAC_HEADER_SIZE, AAC_HEADER_SIZE * 8);

    if(get_bits(&bits, 12) != 0xfff)
        return 0;

    skip_bits1(&bits);          /* id */
    skip_bits(&bits, 2);        /* layer */
    skip_bits1(&bits);          /* protection_absent */
    skip_bits(&bits, 2);        /* profile_objecttype */
    sr = get_bits(&bits, 4);    /* sample_frequency_index */
    if(!ff_mpeg4audio_sample_rates[sr])
        return 0;
    skip_bits1(&bits);          /* private_bit */
    ch = get_bits(&bits, 3);    /* channel_configuration */
    if(!ff_mpeg4audio_channels[ch])
        return 0;
    skip_bits1(&bits);          /* original/copy */
    skip_bits1(&bits);          /* home */

    /* adts_variable_header */
    skip_bits1(&bits);          /* copyright_identification_bit */
    skip_bits1(&bits);          /* copyright_identification_start */
    size = get_bits(&bits, 13); /* aac_frame_length */
    if(size < AAC_HEADER_SIZE)
        return 0;

    skip_bits(&bits, 11);       /* adts_buffer_fullness */
    rdb = get_bits(&bits, 2);   /* number_of_raw_data_blocks_in_frame */

    hdr_info->channels = ff_mpeg4audio_channels[ch];
    hdr_info->sample_rate = ff_mpeg4audio_sample_rates[sr];
    hdr_info->samples = (rdb + 1) * 1024;
    hdr_info->bit_rate = size * 8 * hdr_info->sample_rate / hdr_info->samples;

    *need_next_header = 0;
    *new_frame_start  = 1;
    return size;
}