[vdr] RGB/PAL over VGA at variable frame rate

Thomas Hilber vdr at toh.cx
Wed Jul 23 20:43:43 CEST 2008


On Wed, Jul 23, 2008 at 09:20:08AM +0100, Laz wrote:
> that the only cards that could be convinced to sync at such low rates, 
> i.e. 50 Hz for PAL, were the Matrox G400, G450, etc. Whenever I tried 
> setting modelines with any other cards, I never got any output or an 
> error when starting X.

also Radeons need a special 'invitation' for this by specifying:

Option      "ForceMinDotClock" "12MHz"

> I take it that more modern cards are a lot more flexible in this respect!

maybe. nVidia cards I tested so far work without special problems. But I've
heard that only the closed source driver as capable of 50 Hz for PAL. I did't
test myself the open source driver with that low frequency.

I hope one day the Nouveau project could give us enough support for PAL 
on nVidia with adequate drivers.

> I'm currently using a G450 with softdevice connected to a CRT TV and it 
> works pretty well most of the time with the odd flicker due to dodgy sync 
> every now and than.

maybe you can convince the softdevice developers to give the patch a
try:)

> Using hardware to do the deinterlacing is _definitely_ the way forward, 

for displaying interlaced content it's always the best to use a display
with native interlace capabilities. So nobody has to deinterlace 
at all. You just route the plain fields straight through to the hardware.

> especially for CRT. (Not sure whether LCDs display an interlaced 
> streame "properly" or whether they try to interpolate somehow and refresh 

I've heard modern LCDs do a pretty good job interpreting a conventional
PAL signal. At the expense of huge amount of signal processing circuitry.




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