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TiredLegs
2009-05-29, 05:15
I noticed the other day that many of the pixels on the display of my Squeezebox 2 are not equally bright. My AV receiver has a function that lights up all the pixels on its internal display for a few hours, which restores the pixels to equal intensity. The AV receiver documentation refers to this function as "pixel refresh". Is there such a function for the Squeezebox?

Those of you old enough to remember CRTs for DOS-based computers will recognize that this is the original concept of a screensaver, i.e. to save the screen from deteriorating unevenly.

radish
2009-05-29, 10:24
I can't see how that would work for a VFD (or CRT for that matter) - the pixels have a finite life and get darker with usage. Hence why some are darker than others (they're used more often). Just lighting up the whole display would start wearing them all out equally - but they'd all get dimmer at the same rate so the difference would remain (although non-linear wear might make the difference more/less noticable).

LCDs are a little different in that ghosting can occur temporarily and can sometimes be relieved by holding at full intensity for a while.

TiredLegs
2009-05-29, 10:45
In the case of a CRT, true "screensavers" light up the screen in pseudo-random patterns, which smooth out transitions to areas that have high burn-in.

For VFDs, what you're saying might be true near the end of pixel life, but it doesn't seem to work that way during the bulk of the lifespan. On my AV receiver, for example, which uses a VFD similar to what's in the Squeezebox, it's quite easy to see the intensity even out after all the pixels are lit for a few hours. There's no way that brighter pixels have worn themselves down in that time to the level of other pixels that might have been used hundreds or thousands of hours more. Perhaps it's not the phosphorous elements, but the driver circuitry, that's affected.

radish
2009-05-29, 11:02
Oh I know all about CRT screensavers :) I'm surprised about the VFD stuff, some of my older players have very distinct burn patterns, so if it's fixable I'd be very happy - but no one's mentioned the possibility in previous discussions of screen fade. Shouldn't be hard to rig up an "all on" plugin surely? :)

TiredLegs
2009-05-29, 11:36
On the AV receiver's VFD, the process seems to even out about 80 percent of the difference. After the whole screen is lit up for a couple of hours, you can still make out which pixels get more use but that distinction becomes subtle. When you go back to normal display usage, it's barely noticeable.

Maybe the best way to implement something like this for the Squeezebox would be to randomly tickle the pixels with noise.

aubuti
2009-05-29, 11:55
In the case of a CRT, true "screensavers" light up the screen in pseudo-random patterns, which smooth out transitions to areas that have high burn-in.
Hmm, that was never my experience. My understanding is that screensavers were designed to *prevent* burn-in on CRTs, not remedy burn-in. I was certainly never able to get a screensaver to "erase" the burn-in from the static elements of WordPerfect 4.1 and Lotus 1-2-3 on my first PC....

radish is probably right that an "all pixels on" plugin would probably be ridiculously easy to write. Until that appears to restore stale pixels a good preventative is the FuzzyTime plugin, which allows the date/time screensaver to drift back and forth across the VFD screen. Unfortunately, I don't think it works with the more elaborate screensavers like WeatherTime.

peterw
2009-05-29, 15:22
radish is probably right that an "all pixels on" plugin would probably be ridiculously easy to write. Until that appears to restore stale pixels a good preventative is the FuzzyTime plugin, which allows the date/time screensaver to drift back and forth across the VFD screen. Unfortunately, I don't think it works with the more elaborate screensavers like WeatherTime.

That's right. I've hacked an older version of SuperDateTime to move its info & icons every time it gets a forecast update (using a FuzzyTime API), but the end product is not nice enough for me to feel good sending a patch to Greg (SuperDateTime already displays "fuzzy" time per a FuzzyTime API, it just doesn't move the info around). I'm not aware of anyone else using the FuzzyTime API to move displayed items around on the screen. Another caveat about FuzzyTime is that, contrary to what I wrote in its web page, it's not exactly a drop-in replacement for Date and Time for everyone, as I don't think it displays alarm bell overlays. Hmm, the web page doesn't even mention the feature I added to move the displayed info slowly from side to side. :-(

Another plugin to prevent overuse problems is Auto Dim Display, which lets you configure your Squeezebox displays to go dark between certain hours (when you're sleeping) if they're turned off at the time. A version that works with the latest versions of SqueezeCenter is available from my site, see the URL below.

All my players are SB2/SB3/Boom units, and the only one that I've noticed anything odd with is the SB3 that doesn't use Auto Display. Its left-most pixels seem a little dim. One of other players was put in use about the same time, but that's too small a sample for me to conclude that Auto Display has prevented that problem in my other gear. The difference in brightness is very slight, but I'd love it if a "refresh" plugin could improve the brightness.

-Peter