def get_available_channels(flist):
    """ Returns all available channels in the format *type/channel_no*
    inferred from the first utterance.

    :param flist: A dictionary with ids as keys and file lists as values
    :type flist: dict

    :return: A list of available channels
    """

    if len(flist) == 0:
        return list()

    utt = list(flist.keys())[0]
    channels = list()
    for src in flist[utt]:
        if type(flist[utt][src]) is dict:
            for ch in flist[utt][src]:
                channels.append('{src}/{ch}'.format(src=src, ch=ch))
        else:
            channels.append(src)
    return channels