5700MSC-IP
IP Network Grand Master Clock & Video Master Clock System
Revision 0.2 Page - 49
for an example of a week worth of daily time jams on a dropframe 29.97Hz timecode output. The
pattern of 2 frame and 4 frame adjustments runs over a period of a couple months.
If multiple timecode outputs are set to dropframe counting mode, it is possible that they may jam
differently from each other at the daily time jam event, even if they are set to jam at the exact same
time. This can occur if they were initialized at different times. To prevent this from happening, use the
“Jam all VitcLtc” menu item which forces all timecode outputs to jam at the same instant. This manual
jam is typically done at an innocuous time of day. There is currently no method of forcing multiple units
to jam together at the same time. It can be expected that eventually a 2-frame offset may appear
between dropframe timecode across multiple 5700MSC-IP units.
Figure 3-19: Dropframe Timecode with Respect to Real-time over One Week
3.3.4.5. Color Frame Alignment to PAL
Color frame alignment to PAL video can be enabled for 25Hz LTC timecode and for any PAL sync
(VITC) output or PAL analog TG output (burn-in window). The 25Hz timecode runs at exactly real time
which means it is always possible to jam the timecode output exactly to the system clock. However,
the color frame alignment rule adds additional complexity. The color frame sequence in PAL runs over
4 frames (8 fields), which does not divide evenly into a 25 frame per second count. This means that
color frame 1 lines up with the same frame count only once every four seconds. Therefore color frame
alignment occurs once every 4 seconds.
When a time jam event occurs, the timecode output clock is jammed to the system clock and then
may be adjusted up or down one or two frame counts to match the color frame phase of the reference
or particular black burst sync output. If the frequency reference to the 5700MSC-IP is not phased
correctly with respect to the time reference this can cause a static one or two frame shift for 25Hz
timecode outputs, with respect to the system clock.
If the frequency reference of the 5700MSC-IP is set to GNSS, the time reference will also be forced to
GNSS. The system phase reference is derived from GNSS time, but the system clock is set to UTC
time, which is offset from GNSS time by the total number of leap seconds that have occurred since the
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