| Many folk seem
confused as to what video processors actually are. The common belief is that
they just de-interlace SD material and then rescale it to some other
resolution. Indeed when discussing video processors often the comments are
usually about what de-interlacing chipset is used above anything else. It's
true that those are important features of video processors but there is more
to it than that. How they go about these tasks matter, as do some of the
other features a video processor can have that may offer increases in
performance over in built video processing. Here's some of the things we
believe video processors should do.
Video Processors are the glue that binds together a
video system. Modern displays are not able to display our old and new
television standards without some form of processing being involved. Most of
our video systems at home will have a large and disparate range of sources
with varying output resolutions and refresh rates. None of these sources are
likely to actually output a resolution or refresh rate that is optimum for
our display! Good video processors are able to be configured to optimise the
capture and processing of all these signals and to then output them at the
most appropriate resolution and refresh rate for the source material and the
display. Here are some examples:
|480i (or 576i), often s-video (or by SCART)
NTSC or PAL, Composite video
Region1, 480i@60Hz via Component or possibly HDMI
Region2, 576i@50Hz via Component or possibly HDMI
R1, 480P@60Hz via Component, HDMI or DVI
R2, 576P@50Hz via Component, HDMI or DVI
1080i@60Hz via Component or HDMI
1080i@50Hz or 720P@50Hz via component or DVI HDCP/HDMI
|SD plasma's... and clones
HD 42" plasma...
50" plasma and clones
Alis panels and clones
Pioneer 43" plasma
Pioneer 50" plasma
CRT Front Projection
1280x720 or 1024 x576
1365x1024 or 1400x800 or 1920x1080
1280x720, 1920x1080, 1366x768
Variable from 480P up to 1080P or more!
If you compare the source output resolutions with
the displays actual resolutions you can see why we need video processors.
Standard definition signals in composite, s-video,
component or SCART (RGBcvS) should be able to be processed alongside HDMI,
DVI, RGBHV, or High Definition component. These analogue signals should be
sampled at a very high rate in order to get good, accurate information to
the front end of the system. The Digital inputs meanwhile should be capable
of accepting the full range of signals available from current sources from
480i up to 1080i.
Advanced greyscale, gamma and colour decoding
combined with careful adjustment of input sizing should allow for each
source to be optimised for the most accurate and detailed playback.
Over-scanning of the incoming signals can be minimised and active picture
area being sent to the display should be adjustable to allow the full
picture resolution to be displayed on screen. Digital video levels on input
and output should be selectable for PC or VIDEO dependant on source as
required in order to gain maximum contrast with minimal banding artifacts.
Multiple inputs should allow direct connection of
each source to the video processor, removing the need for switching of video
elsewhere which could degrade the signal quality and which would mean many
components would have to share the same input (compromising one or all of
their picture quality).
Advanced powerful detection algorithms should work
out whether the video material is from original progressive content (film or
PC graphics) or from interlaced video cameras and appropriate processing
then should take place. Original progressive images should be re-constituted
to their full resolution frames then sent on to be up or downscaled to the
required resolution of the display. Accurate frame rate conversion should
then be able to output the progressive frames at the most appropriate rate
eliminating judder and other temporal artifacts. Clever filtering should be
employed to remove harsh digital artifacts like mosquito noise, where
appropriate. Chroma filtering should be assignable on a per source basis for
digital sources with mpeg decoders that suffer from the famous, chroma bug.
Fast processing and as little buffering of the
video signal as possible should be applied in order to minimise potential
lip-sync errors that may require the use of expensive audio delays. This
processing should be able to be updated to add further feature sets or to
aid product compatibility.
If possible multiple memories should be available
to allow quick and simple adjustments for more than one display or perhaps
for day and night-time viewing. The unit, once set up, should be extremely
simple to use.
Advanced RGB gamma and overall LUMA adjustments may
be available on a per input and memory basis. This would allow ISF
calibrators to make very accurate adjustments for greyscale where the
capability wasn't present in the display or where non linear tracking after
calibration required further tweaking.
As we have a mixture of analogue and digital
displays still it'd be wise for the video processor to have analogue outputs
that could be configured for RGB or YPrPb output, preferably on high quality
75ohm BNC connectors where high resolution displays are going to be used.
For digital displays DVI-D or HDMI outputs should be available. The output
resolution and timing parameters of the video processor should be adjustable
in order to create the perfect timings required to minimise artifacts on
screen. In built test patterns should be available to help in set up and
confirmation of ideal video processor/display configuration.
With the advent of High Definition broadcasts more
and more high definition inputs should be available. These inputs
should not just pass through an HD signal. There are many displays that are
not compatible with either the resolutions or the refresh rates of HD
broadcasts. Good video processing should be able to capture these HD signals
and frame rate convert them and scale to allow compatibility with older
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