def METHOD_NAME(self, smil, namespace=None, subtitles_lang='en'):
    subtitles = {}
    for k, ext in [('sMPTE-TTCCURL', 'tt'), ('ClosedCaptionURL', 'ttml'), ('webVTTCaptionURL', 'vtt')]:
        cc_e = find_xpath_attr(smil, self._xpath_ns('.//param', namespace), 'name', k)
        if cc_e is not None:
            cc_url = cc_e.get('value')
            if cc_url:
                subtitles.setdefault(subtitles_lang, []).append({
                    'ext': ext,
                    'url': cc_url,
                })
    return subtitles