Nevion PGM-HD-2x1-PB - Manual (Page 14)

PGM-HD-2x1-PB Rev. B
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5.4.1 Frame sync mode
If a sync input (B&B or Tri-level) is present, the frame synchronizer will output a signal
that has a delay relative to this signal. Two parameters can be set; "Phase delay" and
"Video delay".
Figure 6: Gyda view of the video delay settings
Let us first focus on the phase delay , which also may be called “output phase delay”.
This parameter can be positive or negative, and determines the relationship between
the outgoing video and the sync signal. The parameter really determines a delay on an
internal sync signal, isync
2 . The output is synchronous with isync, see Figure 7.
Figure 7: Positive phase delay
Figure 7 show how the sync signal and the isync signal would look on an oscilloscope,
if converted to analogue signals. The delay of isync can be given in frames, lines, and
samples. The delay can be negative, see Figure 8.
Figure 8: Negative phase delay
The phase delay can thus be written in several ways, a large positive delay will equal a
small negative delay, because there is wrap-around on a frame basis. It follows that it
is not useful to specify a phase delay larger than 1 frame. Strictly speaking the range
could have been limited to -1/2 frame to 1/2 frame. For convenience, the delay range is
allowed to be from -1 frame + 1100 samples to 1 frame
– 1100 samples.
2 Note that isync is not a physical entity, but a term used in this context to explain the delay process and the use of the
configurable parameters related to this process.