def get_subtitles(infile):
    """
    Generator which returns subtitles from a given already opened input file.

    :param infile: The opened file-handle (or file-like object)
    :return: A generator
    """
    line = 'start'
    while line:
        line = infile.readline()
        if not line.strip():
            continue
        st = [line.strip(), infile.readline().strip()]
        line = infile.readline()
        while line.strip():
            st.append(line.strip())
            line = infile.readline()
        yield st
