Slow lock unstable when using Sync Lock Only mode?
- Graham Balchin
The key to the cause of the instability is the use of the “sync lock only” mode. The “sync lock only” mode locks to the line and field information only, it ignores the incoming subcarrier phase and forces the output. For subcarrier phase to be correct, that is ScH=0. \so in this mode this means the output ScH phase will be 0 degrees, not 10 degrees or 20 degrees or any other number. To complicate things, values of 90, 180, or 270 degrees are valid values and simply mean that the 0 degrees point is on another frame.
The corollary of this is that, in this mode, the 8 field sequence of the incoming genlock video is not respected and the output can be 2, 4, or 6 fields adrift.
So in conclusion using “sync lock only” mode?" in this instance is not recommended for the above reason and "manual SC phasing" is the more complete locking mode and we would encourage customers to use this.
Some points to note:
· Slow lock is very slow and can take an hour or more to achieve lock, depending how far out the syncs are. So lock would be achieved but could take a couple of hours.
· If the "manual SC phasing" is first selected, then set to slow lock, the sync will now be stable and remain locked.
· Rather than “sync lock only” we recommend using "manual SC phasing".
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