Acer S271HL software-only strobed backlight

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Re: Acer S271HL software-only strobed backlight

Postby flood » 29 Oct 2014, 01:52

is it possible to control the shape of the pulse?
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Re: Acer S271HL software-only strobed backlight

Postby blargg » 29 Oct 2014, 03:13

Not directly in hardware, which just supports the LED backlight being on or off at any given moment. Via a properly-crafted PWM signal, probably. The driver chip seems to have a minimum LED pulse time of 15us. So if you did some high-speed PWM, you might be able to get a roughly-shaped pulse. I notice that for a 0.2ms pulse (in normal 1kHz PWM dimming), the LEDs don't get to full brightness (looking at a scope connected to a light sensor in front of the display). So you get a little bit of low-pass already.
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Re: Acer S271HL software-only strobed backlight

Postby masterotaku » 29 Oct 2014, 12:09

OMG, why didn't I see this thread before? This is a fantastic modification, and that overdrive modification looks great! I wish I had the knowledge to do this to my BenQ XL2411Z.
CPU: Intel Core i5 4670K @ 4.3GHz
GPU: Gainward Phoenix 1080 GLH
RAM: GSkill Ripjaws X 1600MHz CL7
Motherboard: ASUS Z87-A
Monitor: Dell S2716DG
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Re: Acer S271HL software-only strobed backlight

Postby Q83Ia7ta » 29 Oct 2014, 17:04

May be some crowd funding blargg for buying and tweaking XL2441Z? :)
I'm serious.
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Re: Acer S271HL software-only strobed backlight

Postby Falkentyne » 29 Oct 2014, 17:21

This is AWESOME work.

But the million dollar question:
Can this be done on a Benq Z series?

Even just tweaking the overdrive parameters to remove all of that freaking ghosting....I think masterotaku would LOVE something like this.

Anyone want to send this guy a Z Benq? :)
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Re: Acer S271HL software-only strobed backlight

Postby blargg » 29 Oct 2014, 21:48

Some research shows that it uses the MSTAR brand scaler, not Realtek. It was fortunate that Realtek's ISP protocol gave such extensive access to the device. MSTAR's ISP might only allow reflashing the firmware, which would require disassembly/reverse-engineering to find the places that adjust RTC parameters (finding those in my Acer's firmware took many days of tracing the firmware). The first thing is to find out the exact scaler it uses, and dig up some documentation on its ISP mode to see whether you can avoid having to understand the firmware.
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Re: Acer S271HL software-only strobed backlight

Postby flood » 29 Oct 2014, 22:48

what about whatever is in the gsync upgrade kit for the vg248qe
or the stock vg248qe?

i have no idea where to search for this stuff
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Re: Acer S271HL software-only strobed backlight

Postby blargg » 29 Oct 2014, 22:57

The gsync upgrade kit for the vg248qe PDF has decent pictures of the board. The stock one is an MSTAR (big M logo). The gsync kit has a big heatsink over the chip. Also has some external RAM, and given the newness of gsync, I'd imagine they do more stuff in software.

eBay sales of replacement signal boards provides high-res pictures. Also the service menu sometimes shows the "scaler" which is the chip in question. MSTxxx is MSTAR. RDxxx is Realtek.
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Re: Acer S271HL software-only strobed backlight

Postby Q83Ia7ta » 30 Oct 2014, 13:54

blargg wrote:Some research shows that it uses the MSTAR brand scaler, not Realtek. It was fortunate that Realtek's ISP protocol gave such extensive access to the device. MSTAR's ISP might only allow reflashing the firmware, which would require disassembly/reverse-engineering to find the places that adjust RTC parameters (finding those in my Acer's firmware took many days of tracing the firmware). The first thing is to find out the exact scaler it uses, and dig up some documentation on its ISP mode to see whether you can avoid having to understand the firmware.

Many if not all 24" 144Hz TN monitors uses same scaler: MST 8556T (MSTAR)
http://display-corner.epfl.ch/index.php/BenQ_XL2411Z
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Re: Acer S271HL software-only strobed backlight

Postby masterotaku » 30 Oct 2014, 16:31

Falkentyne wrote:Even just tweaking the overdrive parameters to remove all of that freaking ghosting....I think masterotaku would LOVE something like this.

Haha, you know me well ;) .
Once motion blur and crosstalk are basically reduced to zero, overdrive artifacts are the only thing that keep the motion quality of my monitor from being perfect.
CPU: Intel Core i5 4670K @ 4.3GHz
GPU: Gainward Phoenix 1080 GLH
RAM: GSkill Ripjaws X 1600MHz CL7
Motherboard: ASUS Z87-A
Monitor: Dell S2716DG
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