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

Thomas Hilber vdr at toh.cx
Wed Jul 23 14:16:55 CEST 2008


On Wed, Jul 23, 2008 at 12:12:46AM +0200, Martin Emrich wrote:
> I have connected my VDR box to my TV via a DVI-to-HDMI cable, set the
> resolution to 1920x1080 and let the graphics card do the upscaling
> instead of the TV, because the quality looks IMHO better this way. But

ok. But if doing so you still have to continue deinterlacing in
software. This is because any scaling in Y dimension intermixes even/odd
fields in the frame buffer. Finally producing a totally messed VGA output 
signal.

Scaling in X dimension however is always allowed. E.g. for switching
between 4:3/16:9 formats on a 16:9 TV-set.

> here still the same problem is present, the refresh rate of the graphics
> card is not bound to the field rate of the incoming TV signal, so I can
> either disable sync-to-vblank and have tearing artefacts or enable it
> and have an unsteady framerate.

right. Even if you still must use software deinterlacing for some reason
you benefit from the 'sync_fields' patch. You then can enable
sync-to-vblank and the patch dynamically synchronizes graphics card's vblanks
and TV signal's field updates. Thus avoiding unsteady frame rates at
VGA/DVI/HDMI output.

> I wonder if your patch could be applied to a DVI/HDMI connection, too?
> Its a Radeon X850 currently with xf86-video-ati 6.6.3 and xorg-server 1.4.

In your case the only prerequisite is support of your Radeon X850 by Radeon 
DRM driver. DRM normally is shipped with kernel. So this is a kernel/driver
issue. But I don't expect problems here though I not yet testet the 
X850 myself (yet).

-Thomas




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