Good, i was able to turn on CC on start but i think it will override other subtible if present.
For example, if a stream has CC + Teletext + DVB subtitle, if CC option in MP config is checked, CC will be use by default but we can select another subtitle manually.
Hmmm that will not work correctly, because Core CC Parser is added on graph (needed for now because we can't know if the stream has CC or not).
So it's mean that even if a TVstream doesn't have CC stream, CC will be selected by default. I think it needed a more deep rework to fix that. (Like TsReader tell us if CC are in stream and then add/authorise Core CC parser to be added or not. lol