EVS XT2 - 2-Line Interpolator

XT Series DISK RECORDER – Version 9 - Hardware Technical ReferenceIssue 5.00
EVS Broadcast Equipment SA – April 2008
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To avoid this phenomenon and provide a stable output picture, EVS
developed 2 types of line interpolator: 2-line and 4-line interpolators. The
interpolation process can be enabled or disabled by the operator on all
EVS slow motion systems.
1.5.9.1 2-LINE INTERPOLATOR
The 2-line interpolator actually generates a new field, when the original
field is in parity violation. Each line of this new field is calculated by a
weighted average of the 2 neighbouring lines. This process solves the
problem of parity violation and vertical jitter, but the drawback is a
reduction of the vertical resolution on the interpolated fields, that appear
unfocused. Another by-side effect is the alternation of original fields
(perfectly focused) and interpolated fields (unfocused), resulting in a
"pumping" video signal.
1.5.9.2 4-LINE INTERPOLATOR
The 4-line interpolator uses a more sophisticated calculation based on
the 4 neighbouring 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.
EVS use the same techniques with the Super Slow Motion disk recorder,
working with all models of Super Motion cameras (150/180 Hz). The only
difference between the processing of Super Motion and normal scan
(50/60 Hz) signals is that the interpolator is always
disabled at 33%
playback speed, because the Super Motion signal does not cause parity
violation at this particular speed.
Whatever the choice, the resulting picture is thus always a compromise
between stability and resolution. With EVS systems, the operator always
has got 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.
Default value is interpolator off for all configurations except
SuperLSM configuration in which 4-line interpolator mode is
enabled.