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4-Line Interpolator
The 4-line interpolator uses a more sophisticated calculation based on the 4 neighboring
lines. By using suitable coefficients for the weight of each line in the resulting calculation,
we apply this interpolation to all fields. The final result is a permanently, slightly unfocused
picture. The advantage is a stable output signal with no jitter and no "pumping", but the
vertical bandwidth is even more reduced.
The interpolator is of course always disabled at 100% playback speed, because there is
no parity violation.
Whatever the choice, the resulting picture is thus always a compromise between stability
and resolution. With EVS systems, the operator always has the choice between any of
the 3 above described techniques: no interpolation, 2-line interpolation or 4-line
interpolation. Even if the operator chooses to use the interpolation, this process will be
automatically disabled when not necessary (100% playback for 50/60 Hz signal, 33% and
100% playback for 150/180 Hz signal).
Note
All professional VTRs use line interpolation in PlayVar mode to avoid vertical
jitters.
42 4. Software Specifications
EVS Broadcast Equipment SA Issue 12.05.B - July 2014