Update 7/1/2021: Audiobook Builder 2.1.4 is now available. Grab the update.
Update 6/28/2021: Some folks running macOS 11.3 have reported the same issue. Audiobook Builder 2.1.4 will bring the fix to those users.
A few days ago we got word from a user who saw Audiobook Builder 2.1.2 on macOS 11.4 shorten some of their MP3 files – not always the same files and not other formats, like AAC – as they were added to each project. They sent over a folder of MP3s for us to test and, sure enough, there’s an issue with how AVFoundation, the Apple framework underlying Audiobook Builder’s audio handling abilities, figures out how long some MP3 files are. We say some because the MP3 files we use when testing Audiobook Builder don’t seem to have the same problem, maybe because they have a constant, instead of variable, data rate. It’s not something to worry about when you’re listening to an MP3, as the player reads the file from start to finish and plays whatever it finds, but when you’re moving MP3 data to a QuickTime MOV file, like Audiobook Builder does so it can better handle things when building, you need a precise duration to get the job done. It looks like a recent change in how macOS 11 Big Sur handles things now requires we pass a hint to AVFoundation to read MP3 files from start to finish just to be sure of their duration – so that’s what we’re testing now. It adds a little time to adding MP3 files to your Audiobook Builder projects, but we optimized another piece of that puzzle that just about balances out things so you won’t notice. We’ll have an update out very soon, but if you need anything in the meantime please keep in touch at email@example.com!