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Diamond's VStream wireless HDMI adapter


Where we're going, we don't need wires!
— 1:28 AM on July 13, 2011

Not all of us care to set up and carefully tweak a home-theater PC. Not all of us even bother to acquire set-top devices—PVRs, consoles, or otherwise—that can grab the latest video content from the Internet. For the lazy or indifferent, getting shows from Netflix or BitTorrent into the living room usually involves a plain old HDMI cable, often with a laptop pushing pixels at the other end.

There's nothing technically wrong with that solution, but having a long HDMI cable running across one's living room has some downsides. You've got to unroll the thing, plug it in, and try not to trip over it while walking to the couch with drinks and popcorn obscuring your view. Leaving the laptop next to the TV alleviates the cabling problem, but it means having to get off the couch to control playback. You can forget about loafing around on Facebook while watching the latest Top Gear, too. Ugh!

Wouldn't it be great if you could magically beam video content from your PC to your HDTV without the need for pesky cables?

Thankfully, it's 2011, and such a feat is both possible and easy. The Diamond VStream WPCTV1080H adapter we'll be looking at today promises to augment just about any reasonably quick Windows system with wireless 1080p output capabilities. This adapter's $119.99 asking price might seem onerous compared to a generic HDMI cable, but it's not much pricier than adapters for Intel's Wireless Display technology. WiDi, as it's known, works only with certain combinations of Intel processors and Wi-Fi cards, whereas Diamond's solution requires little more than a free USB 2.0 port and a processor quick enough to do the job.

Specifically, Diamond recommends the use of at least a 2.4GHz Core 2 Duo—an AMD equivalent should do—for an optimal 1080p experience with the VStream. That rules out netbooks and underpowered ultraportables, but today's full-sized consumer laptops and modern desktops should have more than enough horsepower. The included drivers only work on Windows, so Mac users need not apply... unless they'll be loading up Windows via Boot Camp. (An operating system not named after a cat, you say? How terribly unsophisticated.)

If the notion of pushing video content over USB sounds familiar, it might be because DisplayLink has been selling adapter chips that do exactly that for years. We even reviewed one back in early 2008. The VStream WPCTV1080H is simply a new take on the same concept. In spite of the Diamond logo on the box, a DisplayLink chip lurks inside the base station. Sprinkle on some Wireless USB goodness in the form of a pair of dongles, and voilà; that boring old cable has been replaced by a wireless link with a maximum range of 30 feet.

Setup and testing
Getting the VStream WPCTV1080H up and running doesn't involve much effort. The L-shaped USB dongle goes into the desired PC or laptop. The other dongle plugs into the base station, as do the DC power cord and HDMI cable. Get everything powered up, install the required drivers, let the displays flash on and off a few times, and you're good to go. The software might pop up an auto-update request after it's installed, but that only takes a minute. Once everything is set up, Windows essentially treats the VStream like an auxiliary display adapter, and it offers the usual array of multi-display options—mirroring, extending, and so forth.

Audio signals can be passed wirelessly, too. While a normal HDMI connection is able to carry as many as eight audio channels in a variety of formats, the VStream's audio output capabilities are limited to 16-bit, 48kHz stereo. The device's audio component shows up in Windows as a generic USB audio device.

We first put the VStream to the test by playing a 720p H.264 video on a 720p Samsung LCD TV—likely a good representation of what typical users might do. From across the room, the video quality appeared decent, and the frame rate remained smooth overall, save for occasional and brief bouts of choppiness. We also noticed some banding in low-contrast gradients that wasn't in the original video stream. The laptop we used (a 13" MacBook running Windows 7) packs a 2GHz Core 2 Duo, however, which places it a little below Diamond's recommended spec. In any case, the associated audio came through just fine and remained in sync for the duration of the video (about 20 minutes).

Next, we pushed the VStream to its limit by hooking up a 24" HP LCD monitor and setting the resolution to 1920x1080. Since we wanted to test under optimal conditions, we switched off our laptop and connected the L-shaped dongle to a Core i5-750-powered desktop PC. We also left the dongle and base station within a couple of feet of each other.

Pushing a 1080p video stream with eight bits per color channel over USB is no easy task. Uncompressed, you're looking at about 5.9MB per frame, which works out to 178MB/s for a 30 FPS video stream—well beyond the 60MB/s peak bandwidth afforded by the USB 2.0 specification. Considering it's burdened by not only a limited USB 2.0 connection, but also a wireless connection of variable strength, the VStream has to implement some compression mojo to keep images flowing. Otherwise, it wouldn't be able to achieve anything much smoother than a slide show.

Some symptoms of that compression were apparent on our 24" monitor. The text looked garbled and aliased, as you can see below:

We also noticed some color banding in still gradients, and the banding worsened with motion. (I'm guessing one of the compression algorithms involves reducing the color palette.) The image fidelity didn't improve when we bumped the resolution down to 720p, and toggling the "optimize for video" setting in the DisplayLink tray utility didn't help, either. Using our laptop to talk to the 24" monitor wirelessly produced similar results, so this was no fluke. The VStream may do a decent job with video, but users seeking sharp text and pristine 2D graphics will have to stay tethered.

We went ahead and conducted additional video testing on our quad-core desktop PC, using 1080p and 720p versions of the Tintin trailer and a standard-definition Arrested Development stream from Netflix. The 1080p trailer exhibited some choppiness and aliasing. CPU utilization was only around 5-10% higher than normal in that scenario, so the bottleneck clearly lay with the VStream. The 720p trailer looked cleaner, but it also suffered from dropped frames. Even the Netflix video stuttered slightly in parts—nothing serious enough to make the audio go out of sync, though. Incidentally, color banding was more visible in the Netflix video than in the others. Perhaps the higher compression ratio of the source content was the culprit.

Out of simple curiosity, we fired up TrackMania United Forever at a 720p resolution to see if the VStream could handle some 3D gaming. Predictably, frame rates were too low to be playable. You'll want to stick to point-and-click adventure games with this thing.