lexlazootin wrote:Whats the math for vertical total and how long it takes to draw the frame?
When i got my Zisworks monitor i could overclock the VT to 2200~ and Zis said he wasn't able to get his above 1400 and that's why he never FreeSync a shot. He later game me a updated firmware for strobing to work.
How fast is 2200 and how would it compare to 240hz draw times?
Screenshot i sent him at the time since my phone wasn't working:
http://i.imgur.com/gqaK1gP.png
1080p embedded in a 2200p vertical total video signal means the visible image part of the video signal is 1080/2200ths of 1/121th of a second at 121Hz. Mathematically this boils down to a ~1/246th of a second. That's 1080 visible, 1120 blanking -- calculated from (vertical total minus visible equals blanking).
Formula in seconds:
Time spent in LCD scan = (vertical visible resolution / vertical total) x (length of refresh cycle)
Time spent in blanking interval = ((vertical total - vertical visible resolution) / vertical total) x (length of refresh cycle)
length of refresh cycle = 1 / refresh rate in Hz
In this case, you result in approx 0.0042 second (4.2ms) for this situation, for both numbers. Both numbers can be identical (or nearly so) if vertical total is exactly (or nearly) twice the vertical resolution. This means the LCD is spending half of the time scanning, and spending half of the time idling between refresh cycles.
Assuming instant mode operation (darn near directly scan from video signal). LCD scan, meaning "initiating the beginnings of the GtG transition". In most TN LCDs, this is done one pixel row at a time. The GtG completions lag approximately 1ms behind, so in high-speed videos, it looks like a vertical wipe. (Good example is
high speed video of LightBoost). In your situation, if we pointed a high speed camera at this screen, the "vertical wipe" effect of the LCD scan -- would run top-to-bottom twice as fast, and add a much longer pause between refresh cycles.
So basically, for LCDs that are scanned directly from the video signal (instant mode operation) -- then VT2200 means a 121Hz refresh cycle is being scanned top-to-bottom-edge in 1/246th of a second. Basically, twice as fast as a regular 120Hz refresh cycle. You'll be needing the 240Hz LCD overdrive lookup table, for such a fast scanrate, as regular overdrive (tuned for 120Hz) won't necessarily look proper at this scanrate (closer scanrate used for 240Hz).
This produces a vertical blanking interval big enough to drive a truck through -- approx 4 milliseconds (A 120hz refresh cycle is 8.3ms, so that fast scan rate is half that). Assuming a 1ms of LCD GtG for a common TN gaming monitor -- then with with well-tuned overdrive (currently, I'm not 100% sure if zis tunes all G-to-G combinations equally for all scanrates), you could have 2-3ms strobe lengths for a much brighter strobed screen. Or ~0.5ms-1ms for a much-more-strobe-crosstalk-free screen given generous GtG grace period.
