Description from the web.

" An EPUB3 with audio is an e-book that embeds synchronized audio into the text, allowing for a dynamic reading experience where words or sentences can be highlighted as the audio plays. This is achieved using EPUB 3's media overlays and SMIL (Synchronized Multimedia Integration Language), which map text sections to specific audio segments. The format is ideal for interactive content like textbooks, cookbooks, and travel guides, though it requires EPUB3-compatible readers for full functionality. "

Currently Calibre software allows me to generate synchronized AI audio for my EPUB3 books but LingQ does not recognize the audio or the Audio sync timestamp data.

Solution :

Add support for EPUB3 books with already synchronized audio. Import the audio and audio timestamp data from the book.

This feature is in line with supporting faster language learning. It will reduce time lost importing books with built in audio. It will reduce LingQ server load to generate TTS and sync audio. In lingQ Audio currently has to be manually imported, which consume a lot of time.

For further reading.