mpv is so great. It was an immense downgrade to start watching movies on my ps4 with media player, netflix, plex etc. They(mostly media player) have issues on the very basics like pausing and playing video, subtitles, continue watching etc.

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