Pixelchecksum with mouseclick not accurate?

[lacamel]

Hi there,

I did a short script to simulate mouse click when pixel change is detected on a small section of the screen. I recorded the screen many times to see the accuracy of the script and it seems though response time varies widely.

Here's the script 

$checksum = pixelchecksum (400,250, 402,252)

While $checksum = pixelchecksum (400,250, 402,252)

Sleep (50)

Wend

Sleep (300)

Mouseclick("left", 450,300, 1, 0)

Counting from the pixel change to the mouse click, i get response times anywhere between 370ms and 550ms. I've tried running au3 and exe, changed sleep times but never gotten an accurate response time based on the script. Any ideas why?

Edited May 30, 2017 by lacamel
Typo

[lacamel]

When I completely delete the first sleep from the pixelchecksum loop, response time is more consistent. CPU load is minimal.

However, if I set sleep at say 500 ms in the pixelchecksum loop, time lag varies between 150 and 600 ms. How can it be that sleep time is significantly shorter than the value set in this case?

Edited May 31, 2017 by lacamel
Typo

[BrewManNH]

How are you determining the length of time?

[lacamel]

Good question. I used high res video capture of the screen. 

I also noticed that setting the computer in high performance mode helped the accuracy but still getting 50-100 ms  differences. Might be having a processing power issue

Edited June 9, 2017 by lacamel
Typo

[Danp2]

With a longer sleep time within the loop, you have a greater chance for varying response times because the pixel could change at any point during the sleep command. Change occurs early in the sleep cycle yields a longer response time. Change occurs late in the sleep cycle yields a shorter response time.

[lacamel]

Good point Danp2, but a 50ms sleep in the loop does not explain a 100ms lag or more. Eliminating the sleep from the loop does not change that either

[Danp2]

Likely due to other overhead from AutoIT, mostly the call to pixelchecksum.