Minification - used for downscaling images, generally best set to linear
Magnification - used for upscaling images, generally best set to linear
DeInterlace filter - used for deinterlacing, generally best switched off
Postproccessing filter - enables or disables mplayer's post processing, generally best switched off
Auto - automatically configures the post processing filters
Vertical deblocking filter - attempts to remove "blocking" artefacts in the vertical direction.
Horizontal deblocking filter - same but for horizontal.
Auto brightness/contrast - auto adjustment of brightness and contrast (probably better to leave these off and do it manually as the manual controls don't have a cpu hit).
Dering - attempts to remove "ringing" artefacts - when you get bands of brightness around elements of an image in concentric rings. It's the classic jpeg/mpeg artefact.
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