I built on-device TTS app because I run out of audiobooks on a flight

I didn't want to upload my own material to a third party cloud service, use mobile data for voice synthesis and kept running out of podcast queue on flights, so I spent a while trying to get Kokoro running on my iPhone.

LoudReader is what came out of it - an iOS app that reads essays, articles, and books aloud, fully on-device. No account, no network after install.

The model running once reading a sentence was the easy part. Making it not feel like a demo was the rest: streaming synthesis so playback starts before the sentence finishes, porting misaki to swift because I could only find python releases, thermal monitoring and strategy was a tough one as well. Runs well on iPhone 14 Pro(what I have) and newer. Tested on my mom's iPhone 12 Pro and it chokes sometimes, so I ported KittenTTS as a lighter fallback for older devices. The whole project took around 2-3 months on the weekends with claude code and codex.

Smooth TTS was the hard part but the app around it grew larger than I expected with EPUB/PDF import, Gutenberg browsing, a saved-articles queue, multi-week reading campaigns. Happy to dig into any of it in comments.

PDFs, especially academic papers and scanned docs, still annoy me. I built an OCR flow that handles regular documents, but scientific papers with two-column layouts, equations, and fine print are still messy. Curious if anyone here has shipped PDF extraction on mobile that actually handles this well.

This was my first time designing a user-facing product - I'm more of a deep-engineering person so any feedback is welcome too. I'll post a write up on the biggest hurdles in the comments as well.

If you've ever tried to listen to something long on a plane, you get why this exists.