Timing Display
Such cases include timing an NTSC input (multiplier of 1) or a 525 SDI input whose frame time is 33.36 ms (multiplier of 2),
against an NTSC
reference, which has a frame time of 66.73 ms.
Non-integer multiples of reference rates. If you time input rates that are not integer multiples of the reference rates,
the instrument cannot measure the timing deterministically, so it displays the relationships as several circles. Each circle
represents a possible timing offset measurement relative to the reference cross-hair. Display emphasis is given to the circle
that times closest to zero offset and the numerical readouts track this pair. (See Figure 3.)
Figure 3: Timing display of non-in teger multiples of reference rates
Nondeterministic cases include timing of slow rate inputs against fast frame-rate references or when timing video against
film rates.
Multip
le relationships.
For a case where multiple relationships would display, consider an input of 1080p/23.98 Hz with
a reference of NTSC/59.94 Hz:
The different rates result in timing r elationships between the signals that repeat once for every four fields of the input
and five frames of the reference.
Because this allows for five possible ways to measure timing between t hese two signals, the timing display shows four
circl
es, with emphasis and readouts as previously described above.
WFM4000 and WFM5000 Waveform Monitors User Manual 41
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