Sync audiobook with ebook for highlights

[kctdfh]

This is a more involved idea than most others but I think it'd be worth it and on the surface it doesn't seem too insane. It'd work like this:

• You're listening to a book. You pause at the 12h 37m 21s position in the track and click on "show in book".

• Voice looks at the audiobook's directory and finds the only epub file in there.

• It takes the timestamp you're at and splices a +/- 10 seconds segment of your audio file. Ffmpeg can seek fast and cut this super quickly on a 5+ year old Android.

• It then transcribes it. Either using the native API of your phone (e.g. on a Pixel) or through an API call to a self hosted Whisper API or something. Some expected response schema could make it so that the server can be upgradable, as long as it responds as defined.

• Voice then normalized the transcription by removing all the whitespace.

• We also do the same to the epub's content, so with a simple string lookup, we can find the non-whitespace index of the transcription in the book file and then add back the whitespaces and get the index of the string in the book. Could possibly do a whitespace-agnostic search too and skip this and the last step.

• Voice then opens the epub to that character index, allowing the user to highlight the text in an epub-native way.

• We can then extract our highlights from the epub file later.

This is probably way out of scope for your vision of the app but it would solve a major issue with audiobooks that hasn't been solved on Android yet!

[anishbajpai014]

Not looking for exactly this, but just a transcription using something like https://github.com/ggerganov/whisper.cpp/tree/master/examples/whisper.android locally. This could then be synchronized with the audiobook. Created a separate issue for lyrics support at #2275