Another fix for iOS 12.2
Another fix for iOS 12.2

The previous fix (adding `-copyts` to copy the timestamp) did only work until a certain uptime (about 8h) was reached.
Adding ``-timestamps abs`` forces the use of absolute (wallclock) time.
This does for some reason work instead of the (much smaller) timestamps after some hours of uptime...

moritzmhmk/homebridge-camera-rpi