[Openchrome-users] Troublshooting NoScale Problems on VT1622A

[Ivor Hewitt]

On Wednesday 10 May 2006 04:44, Jake Thompson wrote:
> So after alot of playing and tweaking, I am still having the "Green Fade"
> issue with my VT1622A.
>
> Running the display in 720x480Noscale causes a green fade on the top of the
> screen and alot of refresh flicker(enough to give me a headache).
>
> If I run in 720x480Over, these problems disappear, however due to the Over
> scaling video playback is no longer smooth and looks bad.
>
Well according to the table, for NTSC 720x480Over is also an unscaled mode 
which should look the same as 720x480Noscale (it did for me). But it seemed 
the refresh rate isn't calculated quite right for it and it isn't quite, but 
I had no image quality problems.

Can you confirm from your log that 720x480Noscale is definitely being used 
(and not 800x600).... and if so could you quantify "video playback is no 
longer smooth and looks bad"

> Thin white lines and other white object you can notice a flicker, also it
> seems to affect all the pixels across the screen, so you can see a
> difference in the screen along the horizontal where the flickering is
> taking place.
>
That's to be expected. Unless you're talking about something different. The 
unscaled modes are for displaying video playback. If you display computer 
generated images with thin straight lines you will get horrible flicker 
unless the application has been written with "TV knowledge"

(hmm I think we need a wiki FAQ for TV modes)

> The green fade takes about 15-25% of the top of the screen. 
>
Yeah it's green. The ntsc noscale has incorrect timings.

> What else can I do to help resolve this problem, I will try out anything
> you think might help.
>
If 720x480Over works... wait for a bit.... if it doesn't I'll see about 
generating some ntsc tv modes manually with my generator for you to play 
with. At the moment I'm concentrating on getting nice working PAL modes (for 
obvious reasons).

Many thanks,

-- 
Ivor Hewitt.