longer processing time than expected (mp4 audio-only file)

[Former user]

What steps will reproduce the problem? 1. add a mp4 audio-only track (and a txt chapters-file) 2. remux as m4a (the original file was not seekable, because it was the raw stream recorded from internet radio with VLC, hence my need of re-encapsulating it) . Subler correctly imports the original metadata and artwork found in the original file (previously added with Kid3) 3. add to queue, process the file.

What is the expected output? What do you see instead? 1) Given that there is NO conversion (I select PASSTHROUGH), the process is much longer than expected : more than one hour for a 3-hour audio-only file. I tested also on a six-minute long file and the ratio is the same.

sample file included