Lectures and Narrations

One ecosystem, two halves

LN began as an AI experiment in book understanding — using language models to analyze narrative structure, character traits, and scene dynamics — and grew into an end-to-end pipeline for immersive, multi-voice audiobooks.

ln-vox The Creator

An offline, self-hosted AI pipeline that ingests raw text or EPUBs. It orchestrates LLMs to cast characters and direct emotional delivery, then uses local TTS to generate a fully acted, multi-voice .m4b complete with text-to-audio sync markers.

ln-reader The Consumer

A custom Android app built specifically to play these enhanced audiobooks. Chapter-relative scrubbing, sleep timers, and an EPUB companion reader that automatically highlights the text in sync with the audio.

What ln-reader does

A focused, offline audiobook player — no accounts, no streaming, no tracking.

📚

Library

Import .m4b from any SAF source — device storage, Drive, OneDrive, Dropbox…
Grid view with embedded cover art, title, author, and total duration.
Per-book detail: chapter and image counts, plus Open / View images / Remove.

▶️

Player

Foreground media session — background playback from notification & lock screen.
Chapter-relative scrubber showing time-in-chapter and "Chapter N of M".
±10 s / ±30 s skips, prev / next chapter, 0.5×–3× pitch-preserving speed.
Auto-saves your position every 5 s; resumes within ≈5 s on next open.

🖼️

Image viewer

Grid of every image embedded in the m4b.
Full-screen pager — pinch to zoom up to 5×, pan, swipe between images.
Reachable from the library, the player top bar, or the Images tab.

😴

Sleep timer

Time mode — 5 to 90 min presets; pauses with playback, resumes on play.
Chapters mode — end of current, or +2 / +3 / +5 chapters.
Optional 10 s volume fade-out, with Postpone / Dismiss and shake-to-postpone.

⬇️

Downloads

Cloud SAF imports are copied locally so playback streams from disk.
Local imports are referenced in place — no copy.
Phase-aware progress: Downloading → Parsing m4b → done; pick any SAF folder.

📖

EPUB companion + sync

Built-in WebView reader, reachable from the player or the book's "Read" button.
A sync manifest ties audio timestamps to EPUB beats & illustrations.
Auto-follow: highlights the active beat, scrolls, and turns pages as you listen.

EPUB + sync, in detail

Each book can carry two optional companions, attached from its detail sheet. What you get depends on what's attached:

EPUB	Sync	Result
✓	✓	Reader auto-follows the audio: highlights the active `lnvox-beat` span, scrolls to it, and turns pages as playback advances. Scrubber shows tappable image markers.
✓	✗	Plain reader, manual paging only.
✗	✓	Image markers on the scrubber only (no reader).
✗	✗	Plain audiobook.

In auto-follow mode, manually flipping a page pauses following; a Resume button re-engages it and jumps to the current beat. Scrubber image markers sit at each manifest image's position within the current chapter — tap one to open the matching embedded m4b image.

Requirements & honest limits

ln-reader is single-device, offline-first software. Here's exactly what that means.

📱

Requirements

Android 13 or newer (minSdk 33, targetSdk 36).
A file manager or cloud app exposing a DocumentsProvider for your .m4b files — Drive, OneDrive, the system Files app, and most third-party managers work.

Drive folder picking doesn't work for the download-location setting — Google removed tree-picker support from the Drive app. Single-file import from Drive still works.
No cross-device sync. A SAF-based sync feature was prototyped and removed.
No streaming — cloud books are fully downloaded at import and use local storage until removed.
Chapter parsing is Nero chpl only. QuickTime text-track chapters load but show an empty list.
The first embedded image (covr) is the cover; other images appear in the viewer but aren't tied to chapters.
Scrubber markers match images by ordinal index — a marker only appears if the m4b has an image at that index.
Reader highlighting needs matching spans (span.lnvox-beat[data-beat-id]); unmatched beats just don't highlight.
The reader uses the EPUB's own CSS on a forced-white page — no dedicated dark reading theme yet.
Re-importing the same file creates a duplicate (UUID-keyed library, no content hashing).
No resume for interrupted downloads — a killed mid-download is cleaned up; re-import.
Single-device only. Uninstalling drops your library and saved positions.

Build it yourself

Not on the Play Store yet — build from source.

JDK 21 required. From the project root:

$ ./gradlew assembleDebug

The debug APK lands in app/build/outputs/apk/debug/. Install it with adb install.

Architecture, design decisions, and tooling quirks live in the project's DESIGN.md.

Browse the source →