def read_srt_file(filename):
    """
    Read the content of an subtitle file (.srt),

    :param filename: srt filename
    :return: the text content of the srt file as a string
    """
    line_number = 0
    text = ""
    with open(filename, encoding='utf-8') as srt_file:
        for a_line in srt_file:
            line_number += 1
            text += a_line
    return text