Manufacturers of video switchers usually provide a sync light or bar graph to help horizontally time SDI video signals, but provisions are usually not made for checking vertical timing.
After wrestling with this for a while at LBN, we finally figured out a relatively simple method of checking relative vertical (and horizontal) timing of SDI signals.
Actually, once the baseband SD or HD signal is converted to SDI, conventional "sync" signals don't actually "exist" anymore. Instead, H and V timing information is transmitted via "reserved data words." This frees up a lot of real estate previously used for sync to transport ancillary data.
So, the trick is to extract/reconstruct H & V sync (and video) back out of the digital stream to use for timing purposes. What we did at LBN was to use a stand-alone D/A converter (no external reference signal) to feed an analog waveform monitor (which was externally locked to house reference- in this case, analog NTSC black burst.) Timing between the converted signals can then be checked in a conventional manner.
We put the input to the D/A converter on a patch for easy access to switcher inputs such as SDI black and camera signals. An important note: you must legitimately check the inputs to the switcher for timing comparisons, and not use the old NTSC short-cut of checking signal timing at the output of the switcher. Once the signals have been re-clocked in a digital switcher, all bets are off. (We learned this the hard way!)
A last note: You need to use an analog scope for monitoring "analog" timing. Our digital scopes, at least, did not display "sync" along with video. Pulses representing horizontal end-of active video (EAV) and start-of-active video (SAV) are displayable [not really true H sync] but nothing from the vertical interval is displayed. Since sync, per se, doesn't "exist," it must be reconstructed using the D/A converter.
oOo
-Al Stephens
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