Re: Auto backlight management?
On Fri, Apr 25, 2008 at 11:46 AM, C. Scott Ananian [EMAIL PROTECTED] wrote: I have discussed with Chris implementing a hackish low-power mode to demonstrate optimal power management on the Gen 1 hardware to illustrate the potential of the XO. I would really enjoy this feature. I would use it on airplanes to ensure that wireless is disabled, and to get longer battery life. The XO is already the second longest lasting electronic writing device I regularly carry - the iPhone currently wins, but is slower to type on and a pain to retrieve data from. Wade ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
On Sat, Apr 26, 2008 at 06:15:22AM -0400, Wade Brainerd wrote: On Fri, Apr 25, 2008 at 11:46 AM, C. Scott Ananian [EMAIL PROTECTED] wrote: I have discussed with Chris implementing a hackish low-power mode to demonstrate optimal power management on the Gen 1 hardware to illustrate the potential of the XO. I would really enjoy this feature. Me three! If there's any way I can help please let me know. Wade Martin pgpFtFF5NCPv9.pgp Description: PGP signature ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
On Fri, Apr 25, 2008 at 11:05:10AM +0200, Bert Freudenberg wrote: On 25.04.2008, at 10:46, Martin Dengler wrote: On Fri, Apr 25, 2008 at 12:07:12AM -0400, Eben Eliason wrote: It's clear to me that it would be quite useful to have a bright backlight AND black white mode for reading a book at night, for instance, and this isn't possible in the current UI. The camera could be checked once when the device went into/out of ebook mode and the backlight changed appropriately. Malicious software also could snap a picture of the user at that moment. This is the privacy issue that Ivan mentioned, and I agree, we cannot use a camera image for this. Well sure...but it seems to raise slightly different concerns: activating the camera when switching to/from ebook mode would be 1) infrequent; and 2) in response to user action. That seems quite different from activating the camera frequently enough to set the backlight during normal, interactive use, and not in response to any specific user action. For my personal use case, if someone manages to get me to install an activity that gets an up-nose picture of me without my knowledge, only when the back of the screen has hit/left the keyboard top, but my backlight goes off/on if it's dark/light, that'd still work for me. I'll send the patch around if I get to it without any expectation it'll get merged. What I suggested before, but which was not practicable, would be some passive readout-hardware in the camera that only reports a single brightness value. But I was told the current design would require to power the camera on for that. And in a new hardware design it may be cheaper and better to add a photo sensor than this. The activities/projects made possible with a light sensor / the information you describe are very cool. - Bert - Martin pgpZe0NkBw9Tn.pgp Description: PGP signature ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
On Fri, Apr 25, 2008 at 09:47:29AM +0100, Martin Dengler wrote: On Thu, Apr 24, 2008 at 10:54:34PM -0700, [EMAIL PROTECTED] wrote: my machines are out on loan right now. is this monochrome mode the high-res mode, or is this still using multiple screen pixels per display pixel like color does? (or another way to put it, does the screen get much sharper when you do this?) It's the high res mode. It looks really nice. I stand corrected. Doing echo 0 /sys/devices/platform/dcon/output with the backlight off does make displayed text look blurrier to me, though. David Lang Martin Martin PS: might save people looking it up: http://wiki.laptop.org/go/DCON#.2Fsys.2Fdevices.2Fplatform.2Fdcon.2Foutput http://wiki.laptop.org/go/Display#The_theory http://wiki.laptop.org/go/Display#DCON_screen_driver_chip pgpDh8WzgLfdQ.pgp Description: PGP signature ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
Bert Freudenberg wrote: On 25.04.2008, at 10:46, Martin Dengler wrote: On Fri, Apr 25, 2008 at 12:07:12AM -0400, Eben Eliason wrote: On Thu, Apr 24, 2008 at 10:43 PM, John Watlington [EMAIL PROTECTED] wrote: Bert misread the spec. When the backlight is switched off, the screen automatically switches to BW mode. Why would you want to take that out of the control of the user ? It's clear to me that it would be quite useful to have a bright backlight AND black white mode for reading a book at night, for instance, and this isn't possible in the current UI. The camera could be checked once when the device went into/out of ebook mode and the backlight changed appropriately. Malicious software also could snap a picture of the user at that moment. This is the privacy issue that Ivan mentioned, and I agree, we cannot use a camera image for this. What I suggested before, but which was not practicable, would be some passive readout-hardware in the camera that only reports a single brightness value. But I was told the current design would require to power the camera on for that. And in a new hardware design it may be cheaper and better to add a photo sensor than this. The biggest benefit I see from adding this is power savings. The backlight should be automatically turned off when there is enough ambient light, to save power. Switching it back on could easily be done by the user (or automatically for convenience). Hey, why not let the kids build this them self ? Here is a DIY light sensor project: http://www.evilmadscientist.com/article.php/nightlight Karl ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
On Apr 24, 2008, at 10:39 PM, Frank Ch. Eigler wrote: Opportunistic use of the on-board camera and the time-of-day clock could yield such heuristics. Just for reference, in my mind the best mechanism to do this on the current hardware would have been to use the battery-status LED in reverse to detect ambient light level: http://www.merl.com/papers/docs/TR2003-35.pdf. Unfortunately, all the display LEDs on our current hardware are behind drive transistors that make this impractical. For Gen 2, a simple photocell (or LED wired as such) would be sufficient to provide proper backlight power management while preserving privacy. I have discussed with Chris implementing a hackish low-power mode to demonstrate optimal power management on the Gen 1 hardware to illustrate the potential of the XO. Until software catches up, this would disable USB (hence wireless) and SD to allow sub-200ms resume; it might be interesting to make this manually-selected mode also do the camera-as-light-sensor trick to properly manage backlight intensity. The goal of this would be to show what battery life is possible; we could also enable/disable the backlight management separately to justify (or not) inclusion of a light sensor in Gen 2 hardware. --scott -- ( http://cscott.net/ ) ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
Bert Freudenberg [EMAIL PROTECTED] writes: [...] The XO does not have an ambient light sensor. The backlight is not turned off automatically in sunlight. [...] Opportunistic use of the on-board camera and the time-of-day clock could yield such heuristics. - FChE ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
At Thu, 24 Apr 2008 22:43:53 -0400, John Watlington wrote: Bert misread the spec. When the backlight is switched off, the screen automatically switches to BW mode. Why would you want to take that out of the control of the user ? Did he misread the spec? What you wrote here and what he wrote there: - There is, however, a DCON mode specifically designed for the b/w reflective case, the anti-aliasing can be turned off and a color-to- gray mixing turned on, but again, this is done manually (in the current UI it is coupled to turning off the backlight). - sound like the same thing. -- Yoshiki ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
On Thu, Apr 24, 2008 at 10:39 PM, Frank Ch. Eigler [EMAIL PROTECTED] wrote: Bert Freudenberg [EMAIL PROTECTED] writes: [...] The XO does not have an ambient light sensor. The backlight is not turned off automatically in sunlight. [...] Opportunistic use of the on-board camera and the time-of-day clock could yield such heuristics. Yes indeed. I brought this up when we were in the keyboard design phase, but it was determined, quite fairly, to be too much effort for the overall gain, given the other components of the system and state of the software (both then, and now, for that matter). It seems that in the future this is a wise place to spend a little extra time, since it could actually have some high energy saving benefits if done well. Naturally, we could provide a way to turn the mode off in the control panel for that that don't want that kind of micromanagement. - Eben ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
On Apr 24, 2008, at 10:39 PM, Frank Ch. Eigler wrote: Opportunistic use of the on-board camera and the time-of-day clock could yield such heuristics. The camera lights up an LED when enabled, alerting the laptop operator to its use. This privacy-preserving feature would be rendered ineffective if kids got used to seeing the LED flash on and off every so often as the system autonomously attempts to adjust the backlight. -- Ivan Krstić [EMAIL PROTECTED] | http://radian.org ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Auto backlight management?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Jordan Crouse wrote: | On 24/04/08 22:10 -0700, [EMAIL PROTECTED] wrote: | this is the one drawback to the fantasic screen, any light from the | backlight that gets through is colored by the screen. it can be made to | appear white by allowing all three colors through, but it's still colored. | | this means that you can't get high resolution mode with the backlight on. | | No part of that is true. The behavior you describe is a myth, | kept alive by people who misinterpet the display specification. | | You can turn on monochrome mode at any time. Try it yourself: | echo 1 /sys/devices/platform/dcon/output | | Boom - there you go. Monochrome for your pleasure. Nope. Take out your magnifying glass and look: each pixel is either red, green, or blue, even in monochrome mode. Those are not software-controlled filters; they're formed by a fixed physical diffraction grating. Monochrome mode just tells the software to set R=G=B, but with the backlight on only one of those three is actually displayed at each pixel. (This may just be a miscommunication, but we might as well be clear.) One amusing question is: could software potentially set monochrome mode and then use fancy color-adaptive subpixel rendering to do optimized display of fonts and images? Maybe, but at 200 dpi the gains would be small, and the computational overhead would be huge. - --Ben -BEGIN PGP SIGNATURE- Version: GnuPG v2.0.7 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIEXH7UJT6e6HFtqQRAiVKAKCdNl5z/A5scDGndbPHZ1Xvn0LOlQCfSDGP BBDUVl4Ybh2emEb8tVVczmQ= =x4XP -END PGP SIGNATURE- ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
