[mythtv-users] Bob2x with wobbling OSD even at 50 Hz

[Brad Templeton]

> > Each field is generated (on alternate frames) by interpolating the 
> > neighbouring fields - in the case of a hard edges (such as in a font) 
> > this will bleed in to the interpolated field (which being on every other 
> > frame will cause a jitter), it would only possible to get rid of the 
> > problem by overlaying this detail after the deinterlacing has been done 
> > (maybe that's possible in the case of the OSD???) or with some fairly 
> > heavy duty image processing. Most broadcast text should be big enough 
> > not to be made too horrible by interlacing - I can't say I get bothered 
> > by it much although it's there. The OSD is a bit nasty at it's default 
> > size, but I've made mine much bigger and it's now fine. The jittering is 
> > still there - but it's much less perceivable when a field is small 
> > relative to the size of the text, which is why you don't see it much in 
> > HDTV. My view is that the benefits of bob-deint out way this problem by 
> > far - so stick with bob and make you OSD bigger.
> 
> OSD I can live with, but watching eg the news with their box graphics
> makes it look pretty bad (reminiscent of earlier days of cheaper
> computer monitors running at too low refresh rate). I should mention
> that this is an LCD TV, perhaps it looks worse there than on CRT?
> 
> I'd still never choose anything but bob for deinterlacing, but it would
> be nice if it could be improved of course...

Well, I don't know about the flicker, but one thing that would be
lovely down the road would be for the OSD to be drawn at the full res
of the screen, not the res of the image.     When showing a 480i program
on an HDTV, you get a blurry OSD rendered at 480i and upsampled
rather than a crisp high-def one (which you do get watching HD programs.)

Of course, this happens because I presume the OSD is rendered and anti-aliased
into the 480 line frame buffer and then xvideo expands it.   Two alternatives
would include:

    a) Write the OSD, in high-def, into the "pillars" on the sides of an
       HD widescreen.   (No good for those few people with 4:3 HDTVs)

    b) Write the OSD into the xvideo mask rather than the video frame.  In
       the video frame, write an anti-aliased "shadow" for the OSD text in
       the mask.  This would allow good looking, anti-aliased text.  The
       mask is binary (a particular colour, either bright blue or green, is
       replaced with the xvideo frame) but if you do it right it should be
       possible to make something smooth.


However, this remains a bunch of work just for aesthetics.  Though having
OSD in the pillars (perhaps with option to have a very small left pillar
and have OSD on the wide right pillar) has the nice advantage of not blocking
the screen at all.