static int h263_decode_gob_header(MpegEncContext *s)
{
    unsigned int val, gob_number;
    int left;

    /* Check for GOB Start Code */
    val = show_bits(&s->gb, 16);
    if(val)
        return -1;

        /* We have a GBSC probably with GSTUFF */
    skip_bits(&s->gb, 16); /* Drop the zeros */
    left= get_bits_left(&s->gb);
    for(;left>13; left--){
        if(get_bits1(&s->gb)) break; /* Seek the '1' bit */
    }
    if(left<=13)
        return -1;

    if(s->h263_slice_structured){
        if(get_bits1(&s->gb)==0)
            return -1;

        ff_h263_decode_mba(s);

        if(s->mb_num > 1583)
            if(get_bits1(&s->gb)==0)
                return -1;

        s->qscale = get_bits(&s->gb, 5); /* SQUANT */
        if(get_bits1(&s->gb)==0)
            return -1;
        skip_bits(&s->gb, 2); /* GFID */
    }else{
        gob_number = get_bits(&s->gb, 5); /* GN */
        s->mb_x= 0;
        s->mb_y= s->gob_index* gob_number;
        skip_bits(&s->gb, 2); /* GFID */
        s->qscale = get_bits(&s->gb, 5); /* GQUANT */
    }

    if(s->mb_y >= s->mb_height)
        return -1;

    if(s->qscale==0)
        return -1;

    return 0;
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.