Grass Valley 3DX-3901 - Manual (Page 18)

GUIDE TO INSTALLATION AND OPERATION
14 | 3DX-3901
To perform a glitch-free switch between two sources, they must be in the same clean switch region. A clean switch
region is contained within ± ½ line about an H=0 point in the reference signal, as shown by the dotted lines in the
figure. There is a clean switch region centered on every H interval. As you can see, vertical alignment with the
reference is not important for the deglitcher to operate properly.
You may switch between signals A, B or C, without any glitch, and also between signals D
E and signals F G.
Any other transition, like A D, will cause a vertical image shift for one frame.
To determine whether a clean hot switch is possible, you need to determine whether the two input signals lie in the
same clean switch region. There are two ways to measure the position of the signals with respect to the reference:
• Use the deglitcher tab in iControl (Input Deglitcher)
• Use the controller menu in Appendix 2 (video timing in timing to ref).
When the deglitcher mode is on, each of these sources will display the alignment offset between the reference
signal and the input signal. Knowing the offset for both input signals, you can determine if they are in the same
clean switch region. If so, any hot-switch between those two signals will be glitch less.
To determine the limits of a clean switch region, you must know the input’s line length in
μs. The first region is
delimited by +½ line and -½ line of the reference. For example, with a 1080i59 signal the line length is 29.6
μs and
so the first region lies between -14.8
μs and 14.8 μs. Other regions can be found by adding or removing a multiple
of line length to the two boundaries.
Example: for a 1080i59 input signal, we have these clean switch regions:
-1 line and -14.8
μs to 0 line and -14.8 μs
0 line and -14.8 μs to 0 line and 14.8 μs
0 line and 14.8
μs to 1 line and 14.8 μs
etc.