EVS XT Series Technical Reference

XT Series DISK RECORDER - Technical Reference
EVS Broadcast Equipment SA - Nov 2005
Issue 3.0
12
frequency depends upon the chosen playback speed.
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.
2.5.7.1 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.
2.5.7.2 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 do 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 VTR’s 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.

EVS XT Series Specifications

General

Brand	EVS
Model	XT Series
Category	Computer Hardware
Language	English