Deinterlacing is the process of converting traditional Interlaced Video into a Progressive Picture that can be displayed on modern non interlaced display devices such as LCD or Plasma screens.
There is a lot of general information on deinterlacing at Wikipedia in these two articles:
MythTV has several options for Deinterlacing. You can find the configuration options under Mythfrontend->Utilities Setup->Setup->TV Settings->Playback. On Playback Profiles (3/9) edit each entry, The Primary and Fallback deinterlacer may be set on the 2nd sub-page.
- Linear Blend
- Kernel (Less Motion Blur)
- This requires SSE support compiled into your Kernel
- Bob 2X Framerate
- This requires Xv or XvMC video acceleration
- This is also called Line Doubling and more information can be seen here (under line doubling):http://en.wikipedia.org/wiki/Deinterlacing#Deinterlacing_methods
- One Field
- yadif, something apparently Michael Niedermayer wrote for mplayer/ffmpeg that's fast but more CPU intensive than above
If using a Nvidia TV output (composite/svideo) & watching PAL/NTSC signals there should be no need to deinterlace video because the TV output's flicker filter's default setting (of 127) makes interlaced material look perfectly natural - exhibited on FX5200 svideo output - YMMV.