Record continuously in the background, deleting old audio files so your storage doesn't fill up too much. Also known as "time travel recording".
Audio is stored on external storage not RAM, so the length of time which you can "travel back" can be quite long, depending on what settings you configure.
You can install this as a normal non-system app alongside the regular LineageOS Sound Recorder which is a system app.
Circular recordings are stored in the Recordings folder of external storage,
inside a subfolder named after the initial period, e.g. Recordings/Sound record ($initial_date $initial_time)/Sound record ($date $time).m4a.
There are two settings - $period and $number. For each circular recording
(i.e. manual press of the "start" button), we record separate audio files each
lasting for $period, and retain the newest $number of files.
By default, $period = 1 hour and $number = 3.
When you press "stop", the current period is also retained, so in practise
you'll end up with $number + 1 files.
We require battery optimisations to be switched off, as our technique requires automatically restarting the audio recording service from a background service. On Android, this is only allowed for apps that have battery optimisations off.