AudioBookSync

OCR Text Search

Camera scan, book language, indexing and tips

The OCR feature lets you photograph a book page or load a screenshot to find the corresponding position in the audiobook.

How It Works

1

The Vision framework recognizes text in the image — entirely on-device, no internet connection required.

2

The recognized text is matched against the audiobook's transcription index (fuzzy matching).

3

On a match, the player jumps to the detected position. You'll see a preview with a confidence score.

Input Methods

Camera Scan: Photograph a book page directly with the camera.

Photo Library: Select a screenshot or photo from your gallery.

Text Input: Enter text manually or paste from clipboard.

Book Language

Every book has its own language: German, English, French or Spanish. It determines which language the audiobook is transcribed in and which language the scanner uses to read the photographed page — and therefore how reliably text and audio find each other. The language has to be correct before you index a book.

Automatic detection: If an EPUB is linked to the audiobook, the app takes the language from its metadata — both when parsing the e-book and during a library scan, as long as no index exists yet.

Setting it manually: Long-press a book in the library and choose 'Book language' from the context menu. This is the way to go for audiobooks without an e-book, or when the EPUB metadata is wrong.

If you change the language of an already indexed book, the app asks for confirmation and deletes the transcription index — it no longer matches the new language. The book is then re-indexed. The book language applies to the device you set it on and is not synced between iPhone and iPad.

Indexing

For OCR search to work, the audiobook needs to be transcribed and indexed once. This happens automatically in the background — even when the app is not active. Each chapter is processed individually, with the currently playing chapter prioritized.

You can see indexing progress in the library (e.g., '12/24 chapters'). A fully indexed book is shared via iCloud with your other devices.

If the index is still missing, the app tells you before you open the scanner or jump between text and audio — and offers to start indexing right away. Newly imported books are flagged once in the library after a scan.

Transcription Engine

You can choose between two engines in settings:

Apple Speech Framework: Built-in speech recognition, free, on-device.

WhisperKit: Local Whisper model for higher accuracy, runs on Apple Neural Engine.

Tips for Best Results

Ensure good lighting when scanning with the camera.
Hold the camera steady and parallel to the page.
Printed text works better than handwriting.
Make sure the audiobook is fully indexed.
For books in another language, check the configured book language before indexing.