The layer's control timebase, which governs how timestamps are interpreted.
- iOS 8.0+
- macOS 10.8+
- Mac Catalyst 13.0+
- tvOS 10.2+
By default, this property is
NULL, in which case timestamps are interpreted according to the host time clock (
mach with the appropriate timescale conversion; this is the same as Core Animation’s
CACurrent). With no control timebase, once frames are enqueued, it is not possible to adjust exactly when they are displayed.
If a non-
NULL control timebase is set, it is used to interpret timestamps. You control the timing of frame display by setting the rate and time of the control timebase.
If you are synchronizing video to audio, you should use a timebase whose master clock is a
CMAudio for the appropriate audio device to prevent drift. See CMAudioDeviceClock Reference for more information.