Part of macOS
avconferencedCalls and FaceTime
○ Leave it
Handles audio and video for FaceTime and calls.
What it is
Encodes and decodes call audio and video.
Why it might be busy
During a FaceTime or phone call. Usually for the length of the call.
If you stop it
Any call in progress drops. Leave it.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
avconferencedfacetimemessagestoredcallhistoryd
From Procession’s guide, in the words the app shows.