def get_user_bound(info):
    """ user specified bound for measurements filter """
    v = [info['tshift_reference'] - info['tshift_acceptance_level'], info[
        'tshift_reference'] + info['tshift_acceptance_level'], info[
        'dlna_reference'] - info['dlna_acceptance_level'], info[
        'dlna_reference'] + info['dlna_acceptance_level']]
    if v[0] > v[1] or v[2] > v[3]:
        raise ValueError('error on user bound: %s' % v)
    return v
