I've made my own mpv extension for Japanese subtitle analysis too. It can also create Anki cards automatically (with screenshot and audio).
Having a scriptable media player is really something else.
Having a scriptable media player is really something else.
With a computer running mpv and plugged into the TV everything just works and I can trivially fix common issues like subtitle/audio sync with my phone as the remote.
On-topic: mpv seems to have a similar language learning extension to OP https://github.com/oltodosel/interSubs