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Rockbox mail archiveSubject: Survey: how fast is your display?Survey: how fast is your display?
From: [IDC]Dragon <idc-dragon_at_gmx.de>
Date: Wed, 28 Jan 2004 22:53:10 +0100 (MET) Hello, I'd like to make a little survey on the variation of the LCDs. The background is that for halftoning it's desirable to "flicker" the pixels with the same speed as the internal LCD scan. Only then every flicker phase is actually displayed, important for the appearance. If we're too slow, a part of the screen is shown twice, giving that temporal value additional, unwanted "weight". If we're too fast, a part gets not shown at all, therefore losing it. The grayscales look perfect and stable on a nice match, grainy on mismatch. Unfortunately the LCD is internally clocked by an RC oscillator, those are far less stable and reproduceable than a crystal, e.g. depend on temperature. And there is no vsync, scan position readout or other means of feedback. So all we can do is blindly do our best shot. I'd like to find out what a good average value would be. I made a diagnostic plugin to find out your value, see attached. It should be good for Recorder (2MB), V2 and FM, requiring you to run a build not older than 27/01 (when I optimized the LCD code again). Source code is included, if you build your own. It tells the LCD rate by making a pattern which interferes with it. To use it, simply play it. It shows 2 alternating frames, a dark and a light one. The alternation is done by a precise timer which you can tune now, with up and down keys. The goal is to get the screen free of flicker, with only a slow-moving residual artifact remaining that looks a bit like "a school of fish", small black horizontal stripes that chase each other. The rest of the screen may look "cloudy" in varying shades, but is stationary. The pattern may move off-screen for a while, so you may only see the background. I tried to take a picture of it, but it didn't came out well. When tuning, if you see a storm of diagonal patterns, you're way off. If the patterns slow down, you're getting closer. If the patterns move up, you're too fast, compensate by going down. Vice versa, increase if they move down. My display does about 67 Hz when freshly started. It decreases as it gets warmer (charging and prolonged disk activity), can get as low as 61 Hz. How does yours? Thanks for participating, Jörg -- +++ GMX - die erste Adresse für Mail, Message, More +++ Bis 31.1.: TopMail + Digicam für nur 29 EUR http://www.gmx.net/topmail
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