[mythtv-users] HDTV Output/Deinterlacing

Doug Larrick doug at ties.org
Wed Dec 15 11:42:10 UTC 2004

Dave wrote:
> Hi,
>    I've been following this list for sometime now, paying particular
> attention to those who are capturing/outputting HD
>    I've seen a lot of posts from poeple telling others to turn on the
> deinterlacer, or that playback is better with the deinterlacer on. 
> Given that the modelines I've seen are set to output 720p or 1080i,
> what are we deinterlacing for?
>    Assuming that the TV supports inputs of 720p and 1080i, can't the
> original format just be passed straight to the TV?
>    My thinking is (and I'm probably way off :) ) if the TV has a ATSC
> tuner, and both 1080i and 720p pictures look "as expected", there
> should be no loss in quality when feeding a 1080i or 720p input from a
> vieo card.
> What am I missing here?

This *should* in fact work just fine.  Since 6111, nVidia drivers are 
capable of outputting interlaced modes.  Two problems:
* the minute you press that "W" button to scale vertically, your 
interlaced lines no longer line up.
* I'm not convinced the nVidia Xv overlay is doing the right thing when 
presented with interlaced video on interlaced output; it's hard to tell, 
but I think it may be doing onefield deinterlacing, or something 
approaching linearblend.  Pausing some high-motion scene does not 
produce flicker as it should.  Normal (non-Xv) content seems to be 
working fine, so it's gotta be some bug in the driver... if only we 
could see the source :-(

Brad Templeton wrote:
> Many HDTVs only take 1080i.  If they do take both, you would need Myth
> to switch to different modes depending on the recording being played.  I
> don't know if it is smart enough to do that.

This has worked for a while.  Settings->Appearance; 3rd screen or so, 
"Separate video modes for GUI and TV playback."  There's only room for 2 
video modes here (plus a GUI mode) but IIRC you can enter more into the 
database manually.

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