Algolith FLEA HDMI - Compression Artefact Reducer and Digital Video Enhancer

Algolith are a Canadian-based company specialising in image processing hardware and software. The Flea HDMI - distributed in Europe by T+W Marketing - is the smallest and most inexpensive of their HDMI-equipped video processors, and unlike the more expensive Dragonfly model which offers deinterlacing and scaling on top of this unit's capabilities, the Flea concentrates almost exclusively on cleaning digital artefacts (blocky patterns) out of compressed video sources like DVD, Digital Satellite, Cable, and Terrestrial ("Freeview") TV. This means that you can run over-compressed, blocky sources into the Flea, and have it clean them up before sending them to your display.

Appropriately named, the device is incredibly small (far, far smaller than you'd expect from pictures) and with a fairly basic silver finish, it looks almost like a miniature Digital TV set top box rather than a video processing tool. In fact, the Flea is so small and lightweight that it's provided with a weighted stand, to stop it from falling over when it's placed upright in your home theatre set-up.

Most people reading this review will have encountered Noise Reduction in some form or another already, as most TVs now come with a built-in Noise Reduction setting. This isn't the same kind of Noise Reduction as what the Flea offers, though. More often than not, in-TV noise reduction is Temporal Noise Reduction (a.k.a. "3D-NR"), which means that the video processor built into the TV looks at groups of frames and makes decisions on what it thinks is noise by detecting rapidly moving areas, which it then slows down. The problem is that this Temporal Noise Reduction is really most effective on analogue sources that add their own electronic video noise to the picture – like old analogue TV broadcasts (due to be shut off in the UK in 2012), VHS tapes, and for home cinema die-hards, LaserDiscs. As most people will be aware, Digital sources suffer from a much, much uglier kind of "noise" – Compression Artefacts.

Unfortunately, these artefacts are much harder to remove than the simple background interference we were used to back in the analogue days, hence the existence of a dedicated unit like this one to try and remove them. The Flea sets out to provide NR for the digital age by intelligently trying to differentiate compression artefacts from legitimate picture information (an area where cheaper types of MPEG Noise Reduction fall short) and is designed to detect and diminish these ugly problems. Seemingly for added value, the unit also performs some other basic video enhancement functions as well.

Compression Artefacts show up on the picture in two main ways. The first type of problem you'll probably have noticed, especially if you've ever watched a football game on digital TV, is that fast movement will break up into squares with clearly visible edges, revealing a grid structure. These are called "Block Artefacts" (also sometimes called "macro blocking") and appear because of the limitations of both the now old-fashioned MPEG-2 system and a lack of bandwidth. The Flea allows the user to control to what extent this effect is masked, with a function called "Block Artefact Reducer", which detects the grid pattern and blends the edges of the boundaries of the blocks.

The next kind of problem is "Mosquito Noise". It's so named because it almost looks like mosquitoes are buzzing around the affected area and if you're in the UK, you can see it 24 hours a day, 7 days a week on the on-screen news ticker that's at the bottom of the BBC News 24 channel, and to a lesser extent on Sky News. The Flea's "2D Spatial Filter" is used to remove this effect by detecting what it thinks is the noise, and sampling nearby pixels and carefully blending them over the affected area.

Now that you know what the Flea is up against, read on to find out if it really can make all the difference.

Image Quality Test: 2D Animation

To begin with, I tested a 2D animated TV show playing at 480p in my Panasonic DVD-S97 player, running through the Flea. The fourth disc of the Region 1 NTSC Invader ZIM box set contains an alternative version of a 20-minute episode that was apparently included at the last minute, and as such is starved for space on the single-layer disc.


Although this particular series usually consists mainly of flat areas of colour (unlike more complex animation), it occasionally uses a TV scan-line effect for some special effects shots, which I expected the Flea's noise reduction to chomp through and remove. However, I was impressed to see that with the "2D Spatial Filter" on Setting 10/15, the loss of detail was minimal, which proves that the unit is doing a great job of differentiating between compression artefacts and genuine detail.

In addition to Mosquito Noise removal, this 2D Spatial Filter brings a very useful side-effect to the table – it also helps removing ringing, or "halo" artefacts. MPEG compression is actually not directly responsible for this particular annoyance; instead, the DVD producers are largely to blame. During the DVD encoding process, companies often attempt to avoid MPEG compression flaws by pre-blurring (filtering) the picture – in other words, softening fine details to give the encoder less room for error. This tends to cause ringing around high contrast areas, which is then often made worse when the DVD producers add Edge Enhancement (Sharpening) later on. The Flea was able to remedy this problem to a certain extent and create much more natural-looking pictures out of filtered, over-processed material.

Image Quality Test: Live Action

By nature, most 2D animation (unless it's incredibly textured) is easier to treat without too many consequences when compared to live action footage, so this is what I tested next. Finding a live action DVD film with obvious compression artefacts proved harder than finding an animated title that had them, since the deeper look makes the artefacts a little harder to spot (and also harder for to remove). Nevertheless, I eventually decided on a scene from "Amelie" (Region 2 UK release) which takes place in a garden with blowing wind (at 22 minutes, 33 seconds into the film). Mosquito noise is visible around the edges of the branches in this shot, and as expected, a slightly weaker setting was required to stop a loss of detail when compared to the 2D animated footage I'd previously tested. Once correctly set up, the results were definitely visible.


The demo disc that Algolith provided with the Flea was the next disc I tried. Out of all the test sequences here, the one that showed the biggest improvement was what appeared to be a recording of a US digital TV broadcast, showing runners at a sporting event. This is the sort of material that was absolutely ideal to test the Flea, because it featured a large amount of fairly distracting compression artefacts, especially around the painted patterns on the Stadium's ground - which is a fairly complex pattern. The results of this were incredibly impressive, with only a trace of mosquito noise left clinging to the edges of objects.

After being impressed by this, I put the same disc into my computer and ran it through a video processing software tool that features an MPEG Artefact removal function, to see how Algolith's efforts stacked up. The Flea's results were far, far more impressive. The software package's filter eroded the entire picture and made it look like an oil painting, whereas the loss of detail with the Flea was minimal (close to non-existant with lowered settings), once again proving its superiority in differentiating between genuine detail and unwanted artefacts. The same superiority was evident in comparisons to the MPEG Noise Reduction feature built into certain DVD players and TVs - the Flea was, unsurprisingly, better than the functionality found in the Sony KDL-40W2000 HDTV and the Panasonic DVD-S97 DVD player I tested.

Prior to using the Flea, I'd expected to be adjusting the "Block Artefact Removal" option the most (on paper, it certainly sounds like the more important of the two), but I found myself more impressed with the 2D Spatial Noise Reduction. Do remember, though, that when video is compressed with too low a bit-rate, detail is lost in the areas affected by compression artefacts which simply can't be recovered. The Flea can only remove most of the artefacts from the image, not get the lost details back. But, with the right source material, carefully setting the options up can make a noticeable improvement with only a minor detail trade-off. Certainly from a few feet back, I'm willing to bet that most people will find an almost undetectable softening of the image preferable to the compression artefacts.

Nevertheless, the usual warnings of any noise reduction system apply here: it can be a delicate balancing act, and with incorrect settings, you can do more harm than good to the picture. This is why the Flea has such a high degree of customisability, and also why it comes bundled with a demonstration DVD that gives some insight into setting it up properly. As with any type of video processing, users should pay close attention to the adjustments they're making and familiarise themselves with exactly what the options are doing, because depending on what you're watching, you may need to make some adjustments now and then to ensure you're getting the right balance of detail and artefact removal.

Using the Flea to clean up Digital TV broadcasts

Next up, it was time for the most obvious use for the Flea to go through the tests: digital TV, which suffers greatly from too many channels being squashed into too small a space. With that in mind, it might surprise you that this section is placed so far down in this review. Unfortunately, this is because this version of the Flea doesn't do much to accommodate most Digital TV users. Here in Europe, set-top boxes output their signal as analogue RGB video via a SCART connection, which can't be adapted to match the digital HDMI inputs on the Flea without further expense (and further conversion devices). If you have a DVD recorder with a Digital tuner and an HDMI output, though, you'll be able to connect directly, and similarly, Sky HD users will be able to connect their decoder directly to the Flea and see improvements made to SD channels. (If you do this, be sure your Sky HD box is set to output in "Auto" mode, otherwise it'll be upscaling SD channels itself, making them harder for the Flea to work on).


To closely simulate this effect, I instead had to record a DVD with a few minutes of footage from a few digital cable channels and send them to the Flea via my HDMI-equipped DVD player, outputting them in Standard Definition. (The DVD was recorded at the highest possible quality setting so as not to add too many additional artefacts). This area was where I noticed the biggest improvements, because, well, they had the most noticeable compression problems to begin with. For Digital TV channels, I found that the device needed to be adjusted far less and that the 2D Spatial Filter could be set fairly high, for the simple reason that most Digital TV broadcasts are pre-blurred prior to transmission to try and keep compression artefacts to a minimum: there usually isn't enough detail for an aggressively-set noise reduction filter to do much damage, leaving room largely for improvements.

HDTV gets Flea'd

Prior to reading the spec sheet, I'd assumed that the Flea would only work with Standard Definition signals, but it handles most flavours of HDTV, too. The Flea allows you to input 720p, 1080i, and so long as it is the rarer 24p variety, 1080p as well. The more common 1080p/50 and 1080p/60 aren't supported, because the higher frame rates of these formats needs more bandwidth which the Flea wasn't designed to accomodate, which is a shame.

The HD video disc formats - HD DVD and Blu-ray - sometimes suffer from compression artefacts, particularly in the case of Blu-ray where the studios exclusively supporting it still insist on using the now rather dated and artefact-prone MPEG-2 codec (a fault largely related to studio politics, and not the Blu-ray format itself). Sony's American Blu-ray Disc of Silent Hill is an example of a disc that looks largely excellent thanks to its high level of detail, but does indeed suffer from visible compression problems in some scenes, making it a challenging test for an MPEG Artefact removal device.

I played the disc back on a Playstation 3 (currently the best Blu-ray Disc player available) with the player set to output Flea-friendly 1080i video. The results were less distinct here, for the single reason that the compression artefacts on HD resolution images are smaller and harder to spot in the first place. It was difficult to find a setting that preserved all of the detail that this spectacularly focused-looking disc had to offer, so, although the Flea can clean up HD pictures, I'm going to make the perhaps somewhat obvious recommendation that it be used primarily for standard definition, unless the HD content in question is lacking in detail.

Other Processing functions

In addition to MPEG Noise Reduction, the Flea also features "Detail Enhancer", "3D Temporal Filter" and "Dynamic Range Stretcher" options. I left all of these off, but will explain what they all do. Dynamic Range Stretcher appears to be the same trick that almost every consumer TV now offers, and you've probably come across it under the name "Auto Contrast". It wouldn't surprise me if the Flea's version of this trick was a little more advanced, but even still, it simply alters the tonal range to make the on-screen picture appear richer and more vibrant. Algolith themselves recommend it's left off (as do I) so presumably this feature only serves as an added-value incentive.

Detail Enhancer at first glance may look like the "Sharpness" control on your TV, that is, a feature that simply makes all of the edges in the picture harder. However, it's differently named for a reason, as it's more intelligent and more constrained. Set too high, it can still cause ringing in some parts of the picture, but in some very blurry cases, it can be set up so as to give the appearance of a more defined source. Since most DVDs already feature edge enhancement of their own, I usually left the Detail Enhancer off.

3D Temporal Filter is the type of noise reduction also featured in many TVs, which is only really suitable for treating moving analogue noise. Almost no DVDs feature analogue video noise (DVDs of old TV shows would be the most obvious exception), however, it can also be used in conjunction with the 2D Spatial Filter to remove some types of film grain – not something I'd recommend at all for the simple reason that filmmakers choose to shoot on grainy film stock for their own stylistic reasons (it's a characteristic of film, not a fault). The test DVD that Algolith bundle with the unit instructs the user to turn this feature on, and it actually ends up making a grainy clip of Woody Allen talking against a flat background look worse, in this reviewer's opinion. That said, I'm aware that some people prefer film to have a more processed, video-like look, in which case, you may enjoy the 3D Temporal function. Certainly, I found that it could reduce the appearance of some types of film grain without causing additional motion blurring (obviously, provided it was set up correctly).

However, there is a use for the 3D Temporal Filter that won't bring about artistic debate - using it remove analogue video noise that was never supposed to be a part of the picture (which you'd most likely find on the aforementioned old TV shows). This filter definitely helps here, but the usual warning applies - keep it set fairly low, or any details will smear and drag around the screen. Algolith themselves have noted, however, that the older type of analogue background noise is nowhere near as objectionable as the Compression Artefacts we have now, so I don't think the 3D Filter will be the selling point for anyone.

Usability

The Flea's user interface is simple and as a result, is almost entirely fool-proof. Although it's capable of accepting commands from a remote control, this is sold separately. From my experience, if you want to get the absolute best balance of detail and artefact removal, the Flea will occasionally require some slight adjustments. With that in mind, and given the price, I think that a remote control would have been a nice in-box accessory.

This isn't a huge deal however, because the user interface is easy to navigate using the Up, Enter, and Down buttons on the front of the unit. It's laid out in a fool-proof manner, with no complicated menu trees to get lost in - you simply scroll up and down through the options and select the one you'd like. It allows access to the entire suite of image processing functions as well as to a useful "Split Screen" option, which shows one side of the frame unprocessed to allow you to compare it to the tweaked results on the right. There's also an option to shut all the Processing off entirely, as well as an option to display Diagnostic Information and one to aid compatibility with HDMI devices. It's a no-fuss, no-frills interface, and the only way I think it could be improved would be for Algolith to implement some way of letting the user know if they had an item highlighted, or if they were merely scrolling through the list.

The Flea's biggest strength is the degree to which it can be customised. The 2D Spatial NR feature has no less than 15 steps ranging from Weakest to Most Aggressive, and the Block Artefact Reducer setting has 4, which is excellent. Some TV sets offer their own MPEG Noise Reduction facilities, which are far cruder and much less customisable than the processing offered by Algolith's device. For example, one major manufacturer's 2006 line of LCD TVs only offers Low and High settings for MPEG artefact removal, one of which is not very effective, the other of which kills so much detail that the results are hard to watch. Customisability is the key to getting the best results, and the Flea doesn't disappoint here.

A most welcome feature was the fact that the Flea provides per-input settings. There are four profiles which are automatically detected and applied depending on the source: HDMI 1 being fed SD video, HDMI 1 being fed HD video, and the same two for the second HDMI input. This means that you can fine-tune the Noise Reduction options to best suit each connected source, and makes a lot of sense, because HD feeds will typically require less processing.

Something that might prove irritating for some is the fact that adding the Flea to your set-up means that you'll need to do some slight changes of your TV's settings. Running the AVIA Guide to Home Theater disc of test patterns allowed me to confirm that raising my TV's brightness setting was needed to avoid crushing the darkest details out of the picture. (Note that this was with the Flea's Dynamic Range Stretcher function turned off). I'm unsure as to why this is the case because brightness/contrast adjustments aren't advertised as part of the Flea's processing, but no real harm comes of it.

Conclusion

All in all, I was incredibly impressed at the Flea's ability to clean poorly encoded video up, especially 2D animated content. Live Action footage also showed noticeable improvements, although the more detailed nature obviously leaves more room for misconfiguration, so users should take care. And, although I can personally think of fewer uses for it with High Definition content, the Flea could be beneficial here too.


Although this review has been largely positive, allow me to explain my two main gripes with the Flea. The first issue weights the final score quite a bit, and is, predictably enough, its high price. The device is built in Canada and is one of the first examples of a standalone product of this type, so it's not hard to understand why it costs £835. It's a price that may not be incredibly expensive considering that there are fully-fledged video processors featuring 4-figure price tags, but regardless, it's still quite a bit of money. Currently I have a video processor at the top of my list of priorities for improving my set-up, but if you're already covered in that area, then this is a device you should definitely consider.

My second complaint relates to connectivity. Although the back of the case shows what looks like room for more inputs, the Flea has only HDMI connectors - 2 inputs and 1 output. I'm aware that more expensive Algolith products incorporate a better range of inputs, but I can't help but think the designers should have included at least one "legacy" connection, like an S-Video jack, to at least allow for an S-Video capable digital cable, satellite, or "Freeview" box to be directly connected. Sky's HD set-top box can send Standard Definition channels out over its HDMI connection, but even still, devices that output video over HDMI are probably going to be higher quality ones that would be less likely to need the excellent improvements that the Flea can provide. The older, standard version of the Flea featured 1 Component video and 1 S-Video input (and also outputs for both) instead of digital connections. This would at least allow a Digital TV decoder to be connected directly via S-Video, but the problem is that neither of these devices is ideal, input-wise.

Perhaps in the future, we'll see Algolith's very capable artefact removal technology embedded in Set-top boxes and high-end TVs (once the costs have come down, that is), so that it can work its magic without a standalone box. As it stands, they've managed to produce a slightly akward but ultimately very impressive compression artefact removal box, which deserves your attention if you can afford it. If you find yourself lost in "MPEG soup" instead of whatever programme you're supposed to be watching, and can make the necessary connections, then the Flea is a device that you should definitely consider.