2 Then have text content/decoder which can be used-as subtitle or ccap.
4 Doubling-up of subtitle/ccap starts in player: that emits subtitle or closedcaption, writer writes both.
5 libdcp gets closedcaptionasset with some common ground with subtitleasset, maybe
6 add_text_asset() which is called for subtitle + ccap by ReelWriter::create_reel()