_subtitle_streams.push_back (SubtitleStream (v));
} else if (k == "frames_per_second") {
_frames_per_second = atof (v.c_str ());
_subtitle_streams.push_back (SubtitleStream (v));
} else if (k == "frames_per_second") {
_frames_per_second = atof (v.c_str ());