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

Thomas Hilber vdr at toh.cx
Tue Jul 22 23:17:26 CEST 2008


On Tue, Jul 22, 2008 at 07:12:35PM +0100, Gavin Hamill wrote:
> In the inevitable shift towards HDTV and progressive scanning, I was
> becoming increasingly concerned that the countless hours of interlaced
> content would be forgotten in the scramble for new and shiny.

not to forget interlaced formats are still in effect for HDTV. I think
you could recycle the basic idea behind my patch for HDTV as well.

> Indeed, my own VDR FF based system exists in a large desktop PC case
> only because of the enormous (and antiquated) FF card. This project
> leads the way for replacing it with something much more compact, since
> the card runs hot and it's only a matter of time before it dies.

that originally was one of my major motivations. I don't like a huge
VDR box with a FF card in my living room. At least Radeons are also available
in low profile format. So are some budget satellite cards. 

I hope one day we also could support some on-board graphics (like nVidia or
Intel) what would allow tiny VDR boxes with very common hardware.

> Is it likely to work with any newer Radeons, or is it because the RV2xx
> series is the last to have useful full open source drivers? I have a
> couple of RV3xxs (Radeon X300 + X600 Pro) I'd love to try this with :)

the patch from above basically should run with all cards supported by
the xf86-video-ati driver. Just have a look at one of the more recent 
man pages:

http://cgit.freedesktop.org/~agd5f/xf86-video-ati/tree/man/radeon.man?h=vsync_accel

Unfortunately with Radeons we currently have 2 problems unsolved:

1. there appears to be a tiny bug in XV overlay scaling code which
sometimes mixes even and odd fields at certain resolutions. A workaround
to compensate for this is to scale the opposite way. This is done by
xineliboutput option 'Fullscreen mode: no, Window height: 575 px'
instead of 'Window height: 575 px' (as noted in my configuration example).

Overlay XV uses double buffering eliminating any tearing effects. This
works pretty good.

2. the other way to use XV video extension is textured mode. This method
shows very good results. No scaling problems at all. But this code is so 
new (a few weeks), there even does not yet exist proper tearing protection 
for.

So for demonstration purposes I still prefer the overlay instead of textured 
XV adaptor.

> "Apparently, some hardware doesn't support interlaced mode. If you have
> sync problems, check the sync signal with an oscilloscope."  

but we are on the safe side. Radeons do support it:)

> In fact, my biggest problem with this project before now has been the
> manufacture of such an adapter - my soldering skills are beyond poor.

just recycle a conventional VGA monitor cable. So you just have to
fiddle with the SCART side of the cable.

> I don't suppose you'd be willing to make some VGA -> SCART hobby-boxes
> up for a suitable fee? :)

at least this was not my primary intention:)

Cheers,
Thomas



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