def speech_to_text(
    file_name, auth_file='auth.json', output_dir='output', opt_out=False,
    tokenauth=None,
    model='en-US_BroadbandModel', content_type='audio/wav',
    threads=1
):
    """
    Convert given audio file to text.
    """
    # logging
    # log.startLogging(sys.stdout)

    # add audio files to the processing queue
    q = Queue.Queue()
    file_number = 0
    q.put((file_number, file_name))

    hostname = "stream.watsonplatform.net"
    headers = {}
    if (opt_out is True):
        headers['X-WDC-PL-OPT-OUT'] = '1'

    try:
        with open(auth_file) as authfile:
            auth_data = json.load(authfile)
            username = auth_data['stt']['username']
            password = auth_data['stt']['password']
    except:
        raise
    # authentication header
    if tokenauth:
        headers['X-Watson-Authorization-Token'] = (
            Utils.getAuthenticationToken(
                "https://" + hostname, 'speech-to-text',
                username, password))
    else:
        string = username + ":" + password
        headers["Authorization"] = "Basic " + base64.b64encode(string)

    # create a WS server factory with our protocol
    url = "wss://" + hostname + "/speech-to-text/api/v1/recognize?model="
        + model
    summary = {}
    factory = WSInterfaceFactory(q, summary, output_dir, content_type,
                                 model, url, headers, debug=False)
    factory.protocol = WSInterfaceProtocol

    for i in range(min(int(threads), q.qsize())):

        factory.prepareUtterance()

        # SSL client context: default
        if factory.isSecure:
            context_factory = ssl.ClientContextFactory()
        else:
            context_factory = None
        connectWS(factory, context_factory)

    reactor.run()

    value = summary[0]
    if value['status']['code'] == 1000:
        return value['hypothesis'].encode('utf-8')
    else:
        return False