[mythtvnz] Video Motion Blur

[Duncan Kennington]

Quoting Steven Ellis <steven@openmedia.co.nz>:

> David Zanetti wrote:
> > Fairly common problem, most TV encoders are trying to do progressive
> to
> > interlaced conversions and not neccecarily doing a great job of it.
> The
> > video doesn't always line up with the scan lines, and conversion
> between
> > the two is ugly, so the whole thing gets a bit soft.
> >
> > And the original content was interlaced, so you've really got
> > interlaced->progressive->interlaced in there.
> >
> > One of the drivers I have for getting a decent HD set is not really
> all
> > that HD content out there, but so I can drive it over HDMI in a
> > progressive mode and bypass a few conversion steps.
> 
> Tried a number of HD screens over DVI->HDMI and the blur is still high.
> Got a de-interlacer enabled to perform
> 
>  interlaced->progressive
> 
> Still isn't as clear as a DVD player.

I find this with the the (non-HD) plasma I have.  It is a progressive/interlace
problem as David says.  If you drive your display with an interlaced signal
(TV-out off the video card) then the card will be interlacing a progressive
signal which is probably showing a deinterlaced version of an interlaced recording.

To eliminate some of this conversion, driving the display digitally is obviously
a better option, hence using DVI or HDMI.  You can even use VGA or component out
(if you have one of those $400+ NVidia cards) to drive the display
progressively.  This will make your menus and non-recorded stuff look better
(should do, anyway!)

If you play a progressive-scan DVD or AVI file across this progressive picture
you should see pretty good rendering of it.  But you won't see DVD quality
rendering - I agree.  I think this can be for one or two reasons: one: you're
trying to display 25 (or maybe even 30) frames a second on a display that's used
to showing 50 or 60 fields.  24-25 frames is about as slow as you can go before
you start to see the frames individually.  I think this is where you start to
see the frames chopping a bit (the top half of the picture not keeping up with
the bottom) when there is a lot of motion in the picture (like a sports game
with lots of panning).  Two could be to do with the speed at which the signal is
delivered to the display (though DVI must surely be able to keep up) and or the
quality of the source recording (remembering that it was recorded interlaced but
this will never come out properly on a media centre style setup unless you use
something like the PVR-350's TV out.

Progressive scan DVDs do some up-conversion anyway, I think, doubling frames up
for a faster frame rate?

Personally I'm going to try a better graphics card, as rendering of downloaded
HD content (like the WMV samples) is *almost* spot on.  And only over VGA...  

Once that's fixed then I'll start tweaking the capture settings. :)