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

Jens Axboe mythtv-users at kernel.dk
Thu Jun 29 12:11:06 UTC 2006

On Thu, Jun 29 2006, Dan Seddon wrote:
> Jens Axboe wrote:
> > On Thu, Jun 29 2006, Dan Seddon wrote:
> >   
> >> Jens Axboe wrote:
> >>     
> >>> On Wed, Jun 28 2006, Tino Keitel wrote:
> >>>   
> >>>       
> >>>> Hi folks,
> >>>>
> >>>> I managed to get a 50 Hz screen on my TFT to get a stable picture with
> >>>> the bob2x deinterlacer (I use a PAL DVB source). However, it's mostly
> >>>> the same as before with 60 Hz. The OSD is only stable for a few seconds
> >>>> maximum, then it starts to flicker again.
> >>>>
> >>>> What should I do to get a stable picture with bob2x?
> >>>>     
> >>>>         
> >>> I'm in the same boat, 50Hz DVB and bob deint causing flicker on
> >>> horizontal lines such as logos (at least that's where it's most
> >>> noticable). On HDTV you don't see it much, on STDV it's quite horrible.
> >>>
> >>> So I'd very much like to know what can be done about this as well. Bob
> >>> deint is the only usable deinterlacer it seems, the others all look
> >>> horrible in comparison.
> >>>
> >>>   
> >>>       
> >> Unless you have some other problem, this is a side effect of bob 
> >> deinterlacing (the fact that Tino finds it OK for a few seconds if 
> >> baffling) - where the detail is small such as small fonts.
> >>     
> >
> > That's the only issue I have, apart from that picture quality is perfect
> > with bob. The first few seconds is the same here for me, nothing
> > changes from the moment the image is first displayed.
> That's really weird - I'm pretty sure you *should* see it, so maybe you 
> do have something else going on??? Unless the bob doesn't start doing 
> it's stuff for while.

I should see the first few seconds being better, or not? Maybe my
writing above isn't clear, I'm trying to say that there's no difference
between the first few seconds and further on here. At least that's how I
remember it, I'll redo that test on tuesday as well.

> >> 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?
> >   
> That makes sense - I'm using a CRT and LCDs are hell of lot sharper (I 
> say this typing at work on dual montior setup - 1 crt, 1 lcd). Also I 
> sit on the Sofa quite well back - where I can't make it out,  it's there 
> on news banners (but hard for me to see).

Ok, that is probably why I think it's more of a nuisance then :-)

Jens Axboe

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