The chatter about the Belkin PureAV RazorVision started on
the AVS forum quite a while ago. I got the first peek at the unit during CES
2006 in Las Vegas, but I didn’t quite understand what I was looking at –
this unit definitely prompted a closer examination.
Well, I finally got to test a unit, thanks to Belkin’s local dealer. The
PureAV RazorVision (part of Belkin’s PureAV line of products)
promises to increase sharpness and bring out details without adding “halos”.
The unit is quite small in size and is about the size and length of a
typical remote control. It has two HDMI connectors on either side (one for
input and one for output), a min-USB connection (probably for firmware
updates) and a wall-wart power connection.
There are three LEDs and a button for mode selection (Split Ccreen, On or
Off) and a second button with three more LEDs for processing level (Low, Mid,
The RazorVision is designed to be the last stage between
your video sources and display, be they SDTV or HDTV, as long
as they are digital (DVI or HDMI). The unit comes with two cables, where
length and connector type (HDMI or DVI) can be selected upon purchase.
the review RazorVision, I received a set of HDMI to HDMI and HDMI to DVI cables,
allowing me to connect the unit to HDMI sources and connect it to my DVI/HDCP
When sources switch or when communication starts (e.g., HDCP
authentication), the RazorVision shows this by having the lights blink sequentially
on the side of the unit where the connection is currently being “worked on”.
This is very intuitive.
Checking with multiple sets of displays and sources, I only got one
combination that caused the RazorVision problems (HDCP related). This was to be
expected, and I was quite impressed with the unit’s adaptability in this
was unable to check length (I do not own very long HDMI to DVI cables), but
logic dictates that this unit will likely also double as an HDMI or DVI
extender since it should output 5 volts even if the input is a bit weak.
The unit actually does two things: contrast stretching and sharpness
enhancement. Both are done in a very different manner than other video
processors or displays. Typical sharpness filters use convolution matrix
algorithms with a few taps that improve sharpness locally, but also cause
ringing. Ringing appears like ghosts or halos around objects.
RazorVision avoids this by using edge detection and performing processing as an
edge adaptive sharpness filter. The filter can be more easily explained by
using it with test patterns (such as a 60IRE window) - the filter
brightens the edges (this is in the highest settings). This makes the edges
appear sharp. When done with “normal” objects, this edge adaptive technique
does sharpen the image dramatically. However, it also brings out sharpness
artifacts that are normally obscured.
Noisy sources will show up with an exorbitant amount of noise. Digital
compression artifacts (macroblocking) are much more pronounced with the unit,
even when set to Low.
Another interesting process is contrast stretching, which is perhaps done
intentionally or as part of the sharpness filter. The stretching is only done
towards the center of the IRE range (i.e., it won’t make a dark scene
bright). This region- based contrast stretching brings out more detail, of
Pictures stand out more, but so do the artifacts. The sad truth is that
there are simply not enough good sources out there that we can use this unit
with, at present. The picture does look good when you first start using the unit.
However, the more it is used, the more artifacts stand out.
The RazorVision works for both SD and HD sources (most source images are HD) in
every format I tried it with (1080i both at 60 Hz and 50 Hz, 720p, PAL,
Testing gamma with this unit caused some very strange results. I’m
not sure how one can test such a system for gamma adjustment because of how
the edge adaptive algorithms work.
Essentially, certain areas on the image
will have different gamma values. In some areas, I measured a drop of about
0.5 in gamma (gamma in one area dropped from 2.2 to 1.7). The shape,
surroundings, contents of the shape will determine how the unit will process
All tests were conducted with the RazorVision set to Low. At Med/High settings, the
processing is so extreme, the image is too harsh to watch. Belkin should
seriously consider scaling down their algorithms so that what their new
High setting is equivalent to what they currently label Low. I’d be
interested in seeing how it performs with more relaxed filter
To really test the unit out, I brought it to my local HT shop and set it to
Split Screen mode (seen on most of the images here). Half of the people
liked the left (unprocessed) side, while half liked the right (processed)
side (screen shots copyright NBC).
The same people that like to have their sharpness control set to maximum on
their display will like the RazorVision. It is less suitable for those
people who prefer their sharpness settings to be turned all the way down
The moniker RazorVision is perfectly suitable for this
product, as it makes everything razor sharp (bleeding sharp). Too much for
some consumers, just right for others.
It is simple to connect and performs as advertised.
- Ofer LaOr -
Mr. LaOr is Editor of Hometheater.Co.Il, a Hi-Fi
magazine published in Israel. He is also the moderator for the AVS Forum
Video Processing section.