[mythtv-users] Nvidia tvout picture quality

Doug Larrick dougl at charter.net
Tue Sep 14 06:45:35 EDT 2004

David Collett wrote:
> - no deint + no xvmc = total crap (visible interlacing artifacts), CPU=?
> - no deint + xvmc = very smooth, no visible interlacing artifacts (xvmc
> doesnt seem to need a deinterlaced signal?), but visual quality is not
> great(colours not as vibrant, appears 'grainier'), CPU=20%
> - deint + xvmc = smooth, but blocky, the deint seems to screw with xvmc
> to the point where it looks better without it. Also, I have had frontend
> crashes with some deint algos + xvmc. CPU=20%
> - deint + no xvmc = excellent visual quality (varies slightly depending
> on deint algo), but not quite as smooth as xvmc. CPU=60%

A few notes:
The deinterlacing filters cannot run with XvMC turned on.  The decoding 
is done in the video card, so there's nothing to filter.  XvMC does, 
however, pay attention to the deinterlace *setting*.  It chooses one of 
three things:
   - if the video is progressive scan, it send both fields
   - if the video is interlaced and deinterlacing is turned off, it 
sends the first field (poor-man's deinterlacing, same idea as the 
'onefield' deinterlacer.
   - if the video is interlaced and deinterlacing is turned on (doesn't 
matter which method), XvMC uses the equivalent of bob deinterlacing: it 
displays first one field then the other, at double the framerate.

Read a post I made yesterday for a description of what the various 
filters do.

I use no xvmc + bob deinterlace filter for output to my (1080i-native) 
HDTV.  For me this is the best combo.

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