[vdr] Interlacing

[Tony Houghton <h@realh.co.uk>]

I use a Voodoo 3 for TV output, which is much better quality than most
modern cards, but its use of a custom 720x576 PAL mode instead of
processing a more standard PC mode means I have to deal with interlacing
in software. This also depends on what I'm playing. I'm using a Nova-T
in the UK with vdr-xine. Some programmes play OK, mainly films. Some
programmes only play properly with xine's deinterlace option, and even
that doesn't seem to do a great job, introducing jerkiness, although
that could be because my 1.2GHz Celeron isn't powerful enough. Trying to
watch a recording of C4's Scrapheap Challenge proved too much for it.
This might have been because I had some stuff going on in the
background, but it was using < 10% CPU and not making heavy use of the
HD.

I also did some experiments with a recording of some snooker from the
BBC. This was a bit jerky, but at regular intervals, whereas I'd expect
a slow CPU to have more random jerks. I also found that if I played the
snooker back in mplayer with the -sync and -vo sdl options, that did a
better job than xine's deinterlace option. But the same trick didn't
sort out Scrapheap Challenge.

Anyway, I presume the problem with these shows is that they're broadcast
interlaced, and surely the reason for that is to match the interlacing
on the TV, so deinterlacing shouldn't be necessary if the player could
sync the interlacing of the stream to the interlacing of the TV output.
This might be a bit tricky with the Voodoo, because the X modeline I
have to use with it (see below) is not interlaced, so it must be doing
the interlacing in hardware. I haven't worked out whether the software
sees it as a 25Hz or 50Hz mode, but I think it's the latter, in which
case I suppose it would have to provide the user with an option to force
it to sync to even or odd frames IYSWIM.

Does anyone have any thoughts on this?

ModeLine "720x576PAL" 27.5 720 744 800 880 576 581 583 625

-- 
TH * http://www.realh.co.uk