Limiting; Fade To Black - pro bel V6402 HD User Manual

3.4.6

Limiting

PROC AMP Hrd Clip
Since gain can be applied to the D1 signal it is possible to generate levels outside the normal 10 bit gamut
of D1 and so limiting is required. The V64xx Proc Amp normally applies a soft form of limiting that
progressively reduces the gain of a signal as it approaches the limits, either overshoot or undershoot. If
this is not required then it can be disabled on the PROC AMP : Hrd Clip menu.
The limiting that is applied is 'simple' in that it does not ensure that the output is correctly within the colour
gamut, but only that each of the three components (Y, Cb, Cr) remains within the legal 10 bit range.
Certain test patterns, most notable the amplitude ramps, contain data that is within the overshoot and
undershoot areas. If they are passed through the Proc Amp with its default soft clipping then they will be
modified. This means that the EDH value on the output will be different to that on the input. If this is not
wanted then the Hard Clipping can be turned ON, but this is not recommended for normal Proc Amp
operation.
3.4.7

Fade to Black

PROC AMP Fade>Blk
V64xx modules with the VP option fitted include a fade to black facility. This enables the output to be
cleanly attenuated to digital black on receipt of an internal command.
The rate of the fade is fixed at half a second.
Locally the fade can be initiated on the PROC AMP : Fade>Blk menu. This contains both an ON and OFF
command.
The fade can also be initiated over the DART remote control network. The fade will start as soon as the
command is sent.
The output will stay at black until any active control input is released, or the unit is reset. There is no
direct indication on the front panel that the output is being forced to black except for the top level banner,
if enabled.
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V6402, V6404, V6406,V6408
and V6418 HD converters
Issue 6