VIZIO XVT-473SV review: input lag, deinterlacing and upscaling using the piLagTesterPRO
This 1080p IPS Smart TV from 2011 looks great but, has variable and rather high input lag, although it's somewhat competitive for 480i and has excelent upscaling. It retailed for about $1300.
Image quality
Good upscaling is critical for retro gaming. Ideally, all pixels should appear equally sharp and bright (no aliasing), and angled lines should appear smooth, with no jagged, irregular steps. Also important is that the display shows most or all of the pixels it is sent. Often, this is not the case, with some number of pixels cropped from the bottom or top edges. Shockingly, these tests are relevant for modern gaming as well, because even at their native resolution many TVs have aliasing and cropping.
I had to adjust the set to minimize cropping and aliasing, but was very successful! There's almost no need for this table to summarize the results:
| resolution | aliasing | cropping (side, top) |
| 480p/i | none | none |
| 720p | very mild | none |
| 1080p | none | none |
 |
| 480i upscaling (left) vs ideal (right) |
In particular 480i/p looked amazing after adjustment; sharp and zero scaling artifacts (see photo). This is a very impressive result matched by few TVs before or after. Only 720p had an issue, with a slight jaggedness that suggests some pixel-rearranging in order to avoid aliasing, but it's a mild effect. On the whole the upscaling is A+!
It supports local diming with an addressable LED array. This allows very high contrast values for advertising purposes, but looks awful, with halos forming around any bright object on a black background. The first thing you want to do is turn that off!
This TV has "smart" features but at the time of testing (2021) most are no longer supported. But it still works as a dumb TV just fine thank goodness.
The display uses an IPS panel with great viewing angles but noticeable off-angle brightness changes, at least on a very dark background. Noticeable if you are looking for them, anyway. In game it's not distracting at all, in my opinion.
The display has 5 HDMI, VGA, and 1 yPbPr input. I tested HDMI and VGA, and found they performed identically.
Input Lag
I used a piLagTesterPRO to measure input lag. This device sends a frame of video over HDMI and measures how long it takes to display it. This display has a game mode, and with it off input lag was very high and varied between modes. Turning game mode on helped. I toggled all the other display quality settings as well, but did not see any further improvements, however the tests reported below with every "enhancement" set to off.
Complicating things significantly, this is yet another display that does not actually sync refresh to the input signal - instead it fills its own internal frame buffer from the video input and then draws that with a fixed additional delay that is randomly determined each time you turn on the set or switch inputs. Take one example, input lag for 720p can vary from 61.6ms to 73.8ms. What you get seems to be entirely up to chance, but at least the lag is fixed and does not drift while you are playing.
I've elected to report the average lag values here, since that seems fairest, but there's no right answer; for more discussion of this issue see the above link. It's worth noting however, that this kind of changing lag is the hardest for your brain/hands to adapt to. I'd much rather have an extra 12ms of fixed lag added to the display than one like this where sometimes the extra lag is 0, and sometimes it's 12ms.
This TV supports 24hz input at 1080p; but it's a lie: it really draws at 60hz and has to repeat frames in an alternating pattern to approximate 24hz. Very disappointing!
It proudly proclaims "240hz" but this is also a lie, somehow relating to motion smoothing that as far as I can tell makes no difference. It does draw slightly faster than 60hz; it only takes about 12ms to refresh the screen, which would suggest that it's actually running at 80hz (which nicely divides into 240, which probably means they came up with that spec by using blank frame insertion, which does appear to be the case from looking at the brightness values over time). But it just sits idle for the extra 4ms left over in each frame, so it's only refreshing the screen 60 times a second. I hate this whole fake 120/240hz thing that happened in the 2010s.
The maximum input refresh rate for TV modes is 60hz; if you switch it to computer modes it can accept a 75hz signal at sub-native resolutions. This does not improve lag, however, as the TV continues to draw 60 times a second, and just drops all the extra frames.
Input Lag Test Results
I report two kinds of values. 1st response measures how long it takes for the TV to start responding (I use a 5% change in display brightness). This overly optimistic value doesn't tell how long it takes to see anything useful, but matches what other reviewers call input lag. full response is a more realistic measure of lag, and requires the display to reach 80% of full brightness. This combines both input lag and response time, and is closer to what you would actually experience in a game.
I'm including the table to show all the modes I tested but in fact all the modes gave the same result: the first response at the screen top starts at 68ms, and takes 12ms to reach the bottom of the screen. That first response takes about 9ms to develop into the full response (that is, response time). This is true in both interlaced and non-interlaced modes. The deinterlacing method used is clever: when the image is static the full 480 vertical pixels are shown with no blur; but when a region is changing, it uses field doubling in that location only, resulting in a blocky 240 vertical resolution. But because things are moving the resulting resolution drop is well hidden. It's a good method for high speed deinterlacing in action games with great sharp visuals for RPGs as well. It's a shame it's paired with a display pipeline that's so slow otherwise.
I tested both HDMI CEA and DMT modes and VGA input as well, all had the same average lag, and the same level of variability.
Results compared to other displays
To allow quick comparison between many displays I've summarized the results
across all the displays I've personally tested with the piLagTester Pro. Min
lag is the time to the first response, measured where the screen starts
drawing (typically, the top); real lag is the time to the full response,
measured where drawing finishes (usually the screen bottom), i.e. input lag +
scan out + response time. Numbers in red denote average values that can vary by
up to 8ms between power cycles (this TV varies by up to 6ms).
Because this TV is pretty slow overall I'm sorting the list by it's best
performing mode, 480i. Even with this leg up, the TV performs poorly, about 20ms slower than average. On the other hand it's great upscaling means it might be a good
choice for non-action retro gaming.
Conclusion
This is too slow for anybody who cares about input lag. But for folks who just care about nice looking visuals, it's a great choice. And as a general purpose TV it looks great too.
Other models (to avoid)
I tested the XVT-473SV. The XVT553SV seems to have the same specs, so I assume it would perform the same. The XVT373SV and XVT323SV match the series in terms of model number but are advertised as "120hz" so they are likely going to perform differently (maybe even slightly better, since most 120hz TVs draw the screen at 8ms, not the 12 seen here).
Given how badly this one performed, Id' be worried about any Vizio from this era. So the XVT3D650SV, XVT3D424SV, XVT3D474SV, and XVT3D554SV, which are 3D TVs sold at the same time, should be viewed with some concern unless somebody else has published lag values for them.
Comments