Product Review

Belkin PureAV RazorVision Video Enhancement Box

March, 2006

Ofer LaOr



● Improves Contrast
● HDMI Connector on Both Ends
● Switch Enhancement On or Off, or Split Screen,
    to Compare Enhancement with No Enhancement
● MSRP: $275 USA

Belkin PureAV


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, High).

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.

With 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 display.

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 area.

I 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.

The 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 course.

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, NTSC).

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 it.

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 settings.

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 (myself included).


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.

© Copyright 2006 Secrets of Home Theater & High Fidelity

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