I'm trying to digitize a VGA signal with a low-power consumer computer running a consumer OS and am having issues with the stability of the sampling rate.
What I did so far:
- grabbing the green channel of the VGA signal analogue signal
- converting it to a rectangular wave form (so either fully lit pixel or totally dark)
- sampling it with a computer and
- reconstructing the image
Here is an example of a screen I'm trying to capture (640x480x60hz)
And here is a video of the capture my programme made.
The conversion to the rectangular wave loses most luminance information, but that is ok. The issue is that the sample rate is unstable because the sampling programme I wrote is interrupted by OS tasks for a few μs here and there. The timer resolution is also quite low (1 μs).
The image I'm trying to capture has a low rate of change, is mostly still for all practical purposes (so no motion video) and I can take multiple passes at each image.
Is there any way I can reconstruct the image information despite the unreliable sample rate?
edited for legibility