Vizio VX20L HDTV review: input lag and upscaling tested using the piLagTesterPRO

This 720p TV from 2007 is rather mediocre, with variable input lag, aliasing, and in general very little to recommend it for gaming, retro or otherwise. 

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.

The set has no options to adjust cropping/scaling. At least not without the remote. 480i/p is displayed stretched to 16:9.

resolution	aliasing	cropping (top, side)
480p/i	mild	20, 30
720p	bad	30, 40
1080p	mild	40, 60

Aliasing is quite bad at the tv's "native" resolution of 720p. 1080p actually looks better, though of course not all detail is resolvable. Supposedly the actual panel resolution is 1366x768.

The display has 2 HDMI, VGA, and 1 yPbPr input. I only tested HDMI.

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 does not have a game mode; just a game 'color' preset that does not impact lag at all. I toggled all the display quality settings and did not see a consistent effect on lag, however the tests reported are 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 an additional delay that is randomly determined each time you turn on the set or switch inputs, and slowly changes over time.  Take one example, input lag for 720p can vary from 20.4ms to 35.5ms. What you get seems to be entirely up to chance. It can't even properly synchronize the display of this buffer with the refresh rate of the input: if the input is 60hz, then it rapidly drifts out of sync every 10 seconds or so and has to drop a frame. For 59.94 (aka NTSC) refresh rates, it does better, but still drifts out of sync slowly, taking several minutes before it has to drop a frame.

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 16ms of fixed lag added to the display than one like this where sometimes the extra lag is 0, and sometimes it's 16ms.

Full 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 it's final brightness. This combines both input lag and response time, and is closer to what you would actually experience in a game.

	Top		Bottom
Resolution	1st response	full response	1st response	full response
480i	61.0	79.0	77.0	95.0
480p	28.0	46.0	44.0	62.0
720p	28.0	46.0	44.0	62.0
1080p	28.0	46.0	44.0	62.0

    

There's a lot of repeats here - every resolution is the same except 480i, which is 33ms slower (suspiciously, that's exactly the length of two frames of video). 

Interestingly, even upscaling to 1080p doesn't slow the panel down relative to its "native" resolution. 

Results compared to other displays

To allow quick comparison between many display I've summarized the results across all the displays I've personally tested with the piLagTester Pro.  Min lag is the first response at the top of the screen, real lag is the full response at the bottom. 

Display	Year made (TV?)	Native Res	native min lag	native real lag	480i real lag	480p real lag	720p real lag	1080p real lag	native response time	native scan out
Dell E198FPb	2008	1024p	2.7	20.4		39.0	35.0		5.00	12.70
Vizio VO370M	2010	1080p	2.5	23.6	83.0	49.0	47.0	24.3	5.47	15.67
Dell U2410 (game)	2010	1080p	4.0	26.2	62.2	28.3	26.5	26.5	6.00	16.20
AOC/Envision G19LWK	2010	900p	3.1	31.2	39.5	38.7	38.4	37.8	15.50	12.60
Dell E2211H	2014	1080p	3.0	33.6	34.7	34.5	34.1	33.8	15.00	15.57
Panasonic TH-58PE75U	2008	720p	28.0	34.0	34.0	34.0	34.0	34.0	6.00	0.00
Dell 1907FPc	2008	1024p	3.0	34.0		35.9	34.8		15.00	16.00
Corprit D157 (hdmi)	2021	1080p	3.1	34.5	34.9	34.8	34.6	33.9	16.25	15.13
Samsung S27C230	2014	1080p	2.9	36.1		36.6	36.1	37.0	18.25	14.97
Vizio E470VL (vga)	2011	1080p	22.0	39.0		39.0	39.0	39.0	9.00	8.00
Dell U2410 (sRGB)	2010	1080p	20.5	42.8	62.4	45.0	43.1	43.1	6.13	16.13
ACER AT3265	2012	1080p	19.5	43.8	62.7	45.3	43.8	43.8	8.00	16.27
RCA L40FHD41	2010	1080p	20.3	46.6	65.0	48.0	47.0	46.0	9.68	16.63
Sony 40VL130 (game)	2008	1080p	22.8	47.3	66.3	49.0	47.3	47.3	9.08	15.43
Polaroid FLM-373B	2007	720p	28.0	49.0	82.0	49.0	49.0	49.0	7.00	14.00
Philips 42PFL3603D/F7	2009	1080p	29.0	50.0	84.0	50.0	50.0	50.0	5.00	16.00
Emprex HD 3202	2007	720p	27.0	50.5	126.0	51.0	50.0		8.50	15.00
LG 42LC2D	2006	720p	28.3	50.6	54.6	50.8	50.4		6.30	15.95
GPX TDE3245W	2016	720p	28.0	51.0	102.0	51.0	51.0	51.0	8.00	15.00
Sony KDL-46EX400	2010	1080p	28.0	52.0	87.0	52.0	52.0	52.0	8.00	16.00
Toshiba 40L2200U	2014	1080p	30.0	56.0	74.0	56.0	56.0	56.0	10.00	16.00
Vizio VO22L FHDTV10A	2008	720p	28.0	61.0	94.0	61.0	61.0	61.0	18.00	15.00
Vizio VX20L HDTV	2007	720p	28.0	62.0	95.0	62.0	62.0	62.0	18.00	16.00
Sharp LC-C3234U	2009	720p	33.0	64.6	83.6	66.6	64.6		15.00	16.60
Toshiba 46L5200U	2013	1080p	55.0	71.0	89.0	76.0	71.0	74.0	8.00	8.00
Sony 40S20L1	2007	720p	48.4	72.0	90.1	72.9	73.4		9.60	14.00
Samsung LN46C630	2012	1080p	54.5	72.1	90.7	90.3	88.5	72.3	10.00	7.63
Samsung HP-T4254	2011	1080p	69.7	75.7	94.1	76.0	75.7		5.00	1.00
LG 47LW6500-UA	2012	1080p	66.6	80.7	149.7	149.0	81.7	80.9	2.27	11.83
Vizio E470VL (hdmi)	2011	1080p	69.0	86.0	128.0	95.0	95.0	86.0	9.00	8.00

This TV is part of the very large group with an average min lag of 28ms. Most of the sets with variable lag have this value as well, suggesting common components. It's response time is below average, however, so in the end it's in the bottom 3rd of my list.

Conclusion

This would be a poor choice for gaming of any type, particularly retro gaming. Although I didn't bother to watch video on it, my experience using it as a computer monitor suggests the image quality isn't great for natural scenes either.  I would avoid this as a monitor.

Other models (to avoid)

I tested the VX20L HDTV, which is the 20" version. There appears to be two versions:  Based similarities in their names, I suspect that the VX32L and VX37L would perform similarly, just with bigger pixels. However, I've made no efforts to check if their specs exactly match the VX20L  so that's only a quick guess.  Another model of almost the same age, the V022L, has been tested and performs exactly the same as this one.