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Rockbox mail archiveSubject: Re: Survey: how fast is your display?Re: Survey: how fast is your display?
From: Eric Linenberg <elinenbe_at_umich.edu>
Date: Wed, 28 Jan 2004 17:11:31 -0500 As I move to higher values the stripes move to the right and up the screen and as I move lower they move to the left and down.. after about 1 minute of being on they are stable at 68.111 FPS and about 2 minutes later it is stable at 67.792 FPS. If you need any more help I am here. -eric ID> Hello, ID> I'd like to make a little survey on the variation of the LCDs. ID> The background is that for halftoning it's desirable to "flicker" the pixels ID> with the same speed as the internal LCD scan. Only then every flicker phase ID> is actually displayed, important for the appearance. If we're too slow, a ID> part of the screen is shown twice, giving that temporal value additional, ID> unwanted "weight". If we're too fast, a part gets not shown at all, therefore ID> losing it. ID> The grayscales look perfect and stable on a nice match, grainy on mismatch. ID> Unfortunately the LCD is internally clocked by an RC oscillator, those are ID> far less stable and reproduceable than a crystal, e.g. depend on temperature. ID> And there is no vsync, scan position readout or other means of feedback. So ID> all we can do is blindly do our best shot. I'd like to find out what a good ID> average value would be. ID> I made a diagnostic plugin to find out your value, see attached. It should ID> be good for Recorder (2MB), V2 and FM, requiring you to run a build not older ID> than 27/01 (when I optimized the LCD code again). Source code is included, if ID> you build your own. It tells the LCD rate by making a pattern which ID> interferes with it. ID> To use it, simply play it. It shows 2 alternating frames, a dark and a light ID> one. The alternation is done by a precise timer which you can tune now, with ID> up and down keys. The goal is to get the screen free of flicker, with only a ID> slow-moving residual artifact remaining that looks a bit like "a school of ID> fish", small black horizontal stripes that chase each other. The rest of the ID> screen may look "cloudy" in varying shades, but is stationary. The pattern may ID> move off-screen for a while, so you may only see the background. ID> I tried to take a picture of it, but it didn't came out well. When tuning, ID> if you see a storm of diagonal patterns, you're way off. If the patterns slow ID> down, you're getting closer. If the patterns move up, you're too fast, ID> compensate by going down. Vice versa, increase if they move down. ID> My display does about 67 Hz when freshly started. It decreases as it gets ID> warmer (charging and prolonged disk activity), can get as low as 61 Hz. How ID> does yours? ID> Thanks for participating, ID> Jörg Received on 2004-01-28 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |