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Maybe someone here can explain the following weird effect: My previous laptop (an HP EliteBook, the exact model escapes me at the moment) had an issue with Lin
by avian 4y ago
Maybe someone here can explain the following weird effect:
My previous laptop (an HP EliteBook, the exact model escapes me at the moment) had an issue with Linux drivers where it would sometimes crash. When it crashed, the laptop's screen would quickly flash bright-dark-bright-dark... To my eye it looked like one garbage frame with mostly bright pixels and one frame with mostly dark pixels.
Nothing weird so far - just a driver bug right? The weird thing was that when I rebooted the laptop after such a crash, the screen brightness would still slightly, but visibly blink in the same pattern, while the monitor was showing normal boot screen and later the login and desktop. The flashing would get less and less noticeable and kind of ring out by itself after a few minutes. After that the monitor was just working as normal.
I can't think of a good reason why the monitor would keep blinking like that after a reboot. The best explanation I had was that perhaps some kind of adaptive algorithm for image postprocessing in the LCD driver had rolled off into an extreme and needed a while to get back to normal parameters. But it seems unlikely anything like that would have time constants in the range of minutes. The other possibility I thought about was that the blinking after a reboot was just a illusion created by my eyes, but I found that unlikely. I never saw anything similar.
- alin23 4y agoAuthor here. My intuition says that's probably a faulty backlight panel. Not sure if you know that, but the liquid crystal that creates the image and colors is very dark by itself, so behind the crystal panel there's another panel filled with bright white LEDs to project the image into your eyes. Those LEDs can draw a lot of power and get hot, so they need proper passive cooling. In laptops that's usually achieved by gluing the LEDs to the lid and making the whole lid a massive heatsink (if it's a metal lid). It's possible that your backlight panel was overheating for some reason, or maybe it was just drawing more power than the source (old battery?) could provide. That would explain the continous blinking/ringing until the power/temperature stabilized, but it's really just a guess. It doesn't really sound like a software error anyway.
- staindk 4y agoI hoped to see a more solid answer because I caused a (I think) similar thing to happen on a friend's MacBook a couple years ago. I think I was using some utility to force the resolution down from retina levels for some emulated game we wanted to play. Something went wrong and the top ~1/5 of the screen started flickering insanely quickly. We restarted the laptop and the flickering continued. Then I think we turned it off, left it off for a while, then turned it back on. Still flickering. In the end we left the laptop on for a couple hours and it slowly became less flickery until it was eventually entirely back to normal. Super weird. I was so confused and my friend was so nice about it all that I didn't even think to take a video or document any exact stuff we tried aha.
- nyanpasu64 4y agoI managed to create the same effect by playing a video which displayed white and black frames in sequence, without a pre-existing monitor defect: https://www.youtube.com/watch?v=-CIzZv5al2E https://www.youtube.com/watch?v=-CIzZv5al2E I think it's related to LCD inversion (http://www.lagom.nl/lcd-test/inversion.php#clickshow http://www.lagom.nl/lcd-test/inversion.php#clickshow).
- LocalH 4y agoI’ve done this with WinUAE, the Amiga emulator, by running it in the mode where it simulates interlace flicker, and leaving it up too long. It faded, but boy did the flickering stay around for at least 30 minutes.