Nexus 5 backlight changing unexpectedly

Discussion in 'Other Device Manufacturers' started by tbessie, Nov 15, 2013.

  1. tbessie

    tbessie PIM-Loving Maniac

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    RickAgresta and Mi An like this.
  2. Mi An

    Mi An Untethered

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    Thermal throttling. Interesting. To me that'd be a good reason to go custom kernel once there are good ones out there and undervolt and underclock if necessary. Heat has been an issue for me with my Nexus 4, and actually thermal throttling (for the N4, it throttles the chipset, not aware of any brightness throttling) bothers a lot of other users who improve performance through undervolting, though performance has not been a consideration for me. I run in dual core mode with max clocks under gig and am pretty happy with performance.

    I would have suggested another angle if you hadn't found that. Tegra 3 devices do dynamic backlight adjustment based on the content of the screen rather than the brightness of the environment for power savings purposes. It was actually theorized to save more power during video playback than the entire chipset used to play the video. The flickering was worse in the power save mode (Asus has under/overclocking built into their rom), but I think it even exists on other modes, it's just smoother and less noticeable. I saw a lot of threads like this in the transformer forums. I'm guessing that's what jig was suggesting as well.
     
  3. jigwashere

    jigwashere Mobile Deity

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    jig was guessing. And not an educated guess, either. :rolleyes:
     
  4. tbessie

    tbessie PIM-Loving Maniac

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    Yes, I think I saw something like that when I was looking around - something they were calling "aggressive contrast adjustment" or something like that, for power saving.

    - Tim
     
  5. Hook

    Hook Professional Daydreamer

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    It still seems odd that more people don't see it. I'd love to know what the trigger conditions are. My phone can certainly get (normally) hot, but I don't see it. Is it because I normally keep my screen brightness dialed pretty low? I tried maxing it but still didn't see anything --of course, I would probably have to use it that way a day or two to really test it and I'm not going to do that. Given how little it seems to happen from what I see, if it were happening to me, I'd be calling up Google for a replacement.
     
  6. tbessie

    tbessie PIM-Loving Maniac

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    Well, on the one hand, if it's something that happens in all Nexus 5's, I'd feel better because I'd know it wasn't a defect in the phone. On the other, if it was a defect, I'd return it and get another, of course.

    If you put the phone at max brightness (disable auto brightness), and can put a bunch of load on the phone (maybe by running a benchmark test) and then immediately open Chrome to a blank white screen and watch it for about 60 seconds, and do that several times in a row (stress-test/white screen, stress-test/white screen, etc.) you'll likely see it happen, if it's going to happen.

    I've made it happen by loading a big web page or looking at Gmail and scrolling down a lot to put some load on it, then switching to a white screen (or just staying on the current screen if it already has a white background).

    I don't think you'd have to run it all day to see it, you'd just have to do what I describe a few times. Don't take your eyes off of it, because it's not noticeably brighter/dimmer, but you can notice the brightness difference if you are watching while it happens (and it has always happened in less than 30 seconds for me).

    - Tim
     
  7. Hook

    Hook Professional Daydreamer

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    I tried. I never use Chrome, but I set up full brightness, ran Quadrant and immediately launched Chrome and waited 60 seconds. Did this 4 times. On the 4th round, I threw in some Dead Space (FPS game). Did it in a fairly dark room (cloudy out, no lights on). Never saw anything. I don't think my Nexus 5 does this.

    Lucky me, I guess.

    Did get some nice benchmark scores. ;)
     
  8. tbessie

    tbessie PIM-Loving Maniac

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    Well, you're, you're just... WRONG, that's all! ;-)

    Huh, weird that you're not seeing it. I wonder why some would see it and some would not. If it turned it it was a problem with only some units, I wonder if Google would take it back (now that I've thrown out all the original packaging and such).

    - Tim
     
  9. Mi An

    Mi An Untethered

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    It's not too unusual for different chips of the same type to heat up differently. One possibility is that Hook's is running cooler under load than yours (Hookette always was a cool customer). Thus if thermal throttling is to blame, yours would be triggered more frequently.

    Another possibility is that jig's uneducated guess is correct and there might be a setting involved. You mention that you read somewhere about contrast adjustment, that was in reference to the nexus 5/snapdragon 800, right, not some other device? There could be a setting that would reduce that. My experience with tegra's contrast adjustment is that the screen gets brighter on lighter screens (like the white background of Chrome) and darker on darker ones, but perhaps qualcomm is doing it differently (it's not all about changing brightness, I believe I read that as brightness is changing, video settings related to contrast, color etc are being adjusted as well, so there could be more than one way to achieve similar results).

    And finally, are you stock everything, rom and kernel?
     
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  10. Hook

    Hook Professional Daydreamer

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    One possibility is I have almost everything Google sync involved turned off (even Gmail, since I use Aquamail). I even turned off okay Google, which is fun but a battery suck as it is always listening (I guess calling it "OK Google sounded friendlier then calling it "Hello NSA") :rolleyes: No auto-sync photos, none of that stuff. I don't know if that makes a difference or not, but just trying to see what might be different here.
     

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