Just now, I have already visualized a rolling-shutter-detection technique (that the TestUFO Lag Tester may enforce).
Just like my inventions of pursuit camera and frame skipping detector (which may also be built-in to the TestUFO lag tester, to more easily discard bad lag numbers), I'm able to invent various kinds of accuracy-verification mechanisms usable by a web browser.
TestUFO is shockingly brilliant because of the accuracy-verification techniques I've invented (including heuristics to self-detect whenever Chrome Browser stutters) -- it is the world's most trusted browser based web test.
With such position in Blur Busters, comes extreme responsibility in launching a TestUFO lag test that is as equally difficult to use as SMTT. And enforcing the user to do a rolling-shutter verification test built into the lag test, preferably in the same photograph as the lag test
(so publicly posted photographs can be quickly discarded if it shows any one of the following: scanout-distortion error indictor, the exposure-too-long error indictor, or the frameskipping error-indicator ... I intend to build ALL indictators into the SAME photograph! Not an easy engineering feat, but my brain has successfully come up with all error indicators)
I am able to mentally emulate new TestUFO tests in my brain (Just like some people have photogenic memory, I have the ability to emulate a motion test in my human brain long before it has been developed. That's how I invented Sync Track, as well as the optical illusions at www.testufo.com/eyetracking nd www.testufo.com/persistence ...amongst other tests)
To protect Blur Busters reputation,
Blur Busters does not want to pollute the Internet with incorrect latency tests.
There shall be no exceptions.
PERIOD. FULL STOP.
That's why TestUFO is stupendously strict about error-margin-embedding-into-photos (stutter detector indicator, etc) -- it's part of the TestUFO Magic Sauce.
Simply putting the monitors side by side, photographing landscape, and backing away from the monitor so that both monitors only fill 1/4th the height of the photograph, allows a 1/240sec rolling shutter to become a ~1/1000sec rolling shutter. That's because it takes 1/4th the time to rolling-shutter 1/4th picture height.
The scanout error-verifier needs to embed itself into the resulting TestUFO Lag Test photograph -- so if a user photographs too close, it will show. The user can just simply back further away from the monitor, and photograph again. Voila.
The error margin is measurable, so
IF photo doesn't have browser skipping (existing TestUFO stutter alarm)
AND IF photo doesn't have frameskipping (single-refresh version of existing test )
AND IF photo doesn't have exposure-too-long indicator (new TestUFO error verifier)
AND IF photo doesn't have scanout distortion indicator (new TestUFO error verifier)
THEN TestUFO Lag Test is likely valid (with caveats)
All embedded in the SAME photograph (thanks to my mental ability to emulate TestUFO test in my brain long before I create them)
I can then easily dismiss those bad photographs. TestUFO stays trustworthy as a result!
My visualization of a modified frameskip test is a single-frame detector (not multiframe detector) since photographing will overlap only 2 refresh cycles, and I just need to verify that they're both adjacent refresh cycles on both displays. This may miss frameskips that occur in non-displayed refreshes for large lag differentials (e.g. monitor A showing fragments of frame #1/#2 and monitor B showing fragments of frame #4/#5) but as long as portions of all contiguous frames (#1/#2/#3/#4), fragmented on either display, then a frameskip almost certainly didn't happen, and repeat photographs will easily reconfirm consistent lag differentials for sample-and-hold displays.
There are other error margins, such as latency induced by mirroring (which may be an active repeatering operation, or an active GPU driver operation), but most of this can be caught by simply swapping the two physical monitor connections afterwards and re-testing, making sure that multimonitor numbers correctly invert (2 becomes 1, and 1 becomes 2) when you re-plug, before re-mirroring. Typically, most of the "mirroring lag error" can be caught this way.
There are additional black-box limitations, like if you're comparing a HDMI-only display versus a DisplayPort-only display, but even the GPU mirror lag can be pre-verified with a couple of duplicate DP displays or HDMI displays -- the mirror lag is often less than 1ms in many cases nowadays, but more testing is needed to verify if that's consistent throughout many high-performance GPUs. We're mainly interested in lag differentials (A versus B) so a fixed mirror lag for both displays is fine, since it becomes equal lag offsets.
This is in addition to my new SMTT-matching algorithm that I've come up with, that allows replicating SMTT with simple VSYNC ON (framerate=Hz motion, rather than 1000fps VSYNC OFF). It's still important to remind users that this is a mainly latency-differential test (A versus B), rather than an absolute-latency test, though a CRT is frequently used as a zero-lag reference, to determine absolute lag with a lag-differential algorithm like SMTT.
Blur Busters prefers to release a different lag test before releasing the TestUFO lag test
However, I prefer to release the commercial Blur Busters lag-testing hardware accessory, before I release this TestUFO lag test. For now, we use the accessory as part of testing monitors internally for the Blur Busters Approved programme (kind of an internal private beta test).