RFC: Xv field order

[Benjamin M. Schwartz]

Ville Syrjälä wrote:
> On Tue, Jun 23, 2009 at 08:08:38PM +0200, Krzysztof Halasa wrote:
>> Thomas Hilber <xorg at toh.cx> writes:
>> Come on, playback of interlaced video only makes sense with vertically
>> unscaled display.
> 
> Not true if you can scale the fields independently.

Even with scaling, it's not a great idea.

Interlacing is a psychovisual hack, designed to make use of your eye's
motion-compensation and spatiotemporal interpolation systems.  It only
works if the scan lines not present in each frame are black, because your
persistence of vision will fill in the black lines with the correctly
motion-compensated contents of the previous frame.

If you scale each field to fill the frame, you will perceive significant
flicker and blurring of fine detail.  The only way to reproduce the
interlace effect correctly is to leave half the lines black in each frame.
 If you are scaling, this is basically impossible, unless you are scaling
up by a factor of at least 2.

A good deinterlacer is a much more general solution.

--Ben

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