Nevion UDC-3G-XMUX4+ - Manual (Page 34)

UDC-3G-XMUX4+ Rev. C
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3.7 Frame synchronizer
The frame synchronizer consists of a frame store buffer and some control logic. The frame
store buffer can store up to 4 full HD frames. Data is fetched from this buffer according to the
user settings by force of the control logic. The control logic sets the frame synchronizer into
different modes dependent on the presence of a sync input.
3.7.1 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. This parameter is called "Phase delay".
Figure 20: Multicon GYDA view of the video delay settings
Phase delay may also 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 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.
The lines are measured in units of the output SDI video standard. If the output SDI standard
is 1080i25, a delay of one line is equal to 35.5us. If the output SDI standard is 720p50, a
delay of one line is equal to 26.6us. If the output SDI standard is 625i25, a delay of one line
is equal to 64us.
For a scenario where the card receives different HD video standards, (e.g.
1080i25 and 720p50) the user may want to conserve a specific delay in
microseconds for all HD video standards. This is accomplished by specifying the
delay in number of samples instead of lines. (For HD video standards the sample
frequency is equal over standards, but the line and frame frequencies are
different for the different standards).
If video input disappears
Given that stable SDI input and sync input exists: If the SDI input disappears, the picture will
freeze for <hold time> and then go to video generator if the card is in default configuration.
If video input reappears
Given stable sync input, the video will reappear after <lock time> of locked video input if card
is in default settings.
If sync input disappears
Given that stable SDI input and sync input exists: If the sync signal disappears, the card will
act as in frame delay mode, see Chapter 3.7.2.
NOTE: This will result in a frame roll as the delay changes.
If sync input reappears
Given that a stable SDI input exists: If the sync signal reappears the delay mode will change
back to Frame Sync mode. Hence the internal clock will be locked to the sync signal and the
delay will again change.
NOTE: This will result in a frame roll as the delay changes.
If both signals disappears