flood wrote:i thought the main difficulty is in strobe length rather than strobe timing...
Correct timing the strobe to happen
is not really difficult since the vsync signal is the trigger, after that the display will be refreshed the time it takes to activate all the pixels is also fixed (maximum refresh rate). Next you wanna know when the last pixel is finally transitioned to another color. This should ideally be the vblank time. Next the strobe will happen which will light up all those pixels which reside in the dark. But here the biggest problem starts since you need to know how long you want to strobe. This needs to be done extremely precise (microsecond accurate) as mentioned earlier in the thread by mark.
For this there currently is no implementation in the monitor to acount for this. I suggested controlling the length by software since I thought this would be possible but alas it is not.
What Mark suggested atleast I hope I interpeted it right is by gradually allowing the backlight to light up following some kind of sine wave like trajectory during the vblank. And during every vsync calculate the light intensity of the strobe in case of pwm a longer strobe and pwm free a gradually increasing light intensity (sine wave). So during fast framerates you will have these short but really intense strobes and while frame rates lower you will have these softer sine waves(in case of pwm free) until some limit and then it will not at all be using strobing anymore but will stay constant.
Think of it as throwing a rock in a pool of water first you will get violent fast waves which will turn into ripples which will finally turn into a smooth surface. Here the rock is the vsync signal the violent wave/ripple the strobe.
The slope after the sine wave should mirror the slope before the sine wave since this will smoothly decrease the brightness while keeping average brightness intact. Maybe some paint will help I hope this is an accurate way to describe it since Mark uses a flat line in his examples but not different frequency's in a single line. The red line is the average brightness needed to be obtained note that the straight slope before it will flat line this is the brightness increase while it is waiting in vblank. In reality this line will probably have a lot more curve into it but drawing that is rather painfull to do with this mouse.
flood wrote:surely it can't be too difficult to strobe for a fixed amoutn of time after each refresh
So you see it is not a fixed amount of time that it needs to be strobed which is exactly the problem. The strobe should follow some kind of smoothly increasing line to atain average brightness in lower frame rates.
Trip wrote:But this creates brightness issues since the strobes are still the same length but happen less often. These last two parts are what people now try to fix and especially the latter part is really tought to implement right now(brightness problem).
Maybe I wasnt clear but the stuff in italics has to do mostly with strobe length not with the timing (when to strobe).