[mythtv-users] Having problems / Need info on BOB Deinterlacing

[James Buckley]

Actually, I'm wrong. Linear blend, or kernel, (and don't quote me on this,
this is just my understanding), convert [x] interlaced frames into [x]
progressive frames, by guessing at the missing content. Seeing how BOB is
listed as giving 2x framerate, that must mean 2x the others (IE linear blend
and kernel), therefore BOB deinterlacing must give [2x]. So for example with
PAL TV, BOB must give a 100fps output. Therefore BOB deinterlacing is best
used with a monitor that can have a 100Hz refresh. The reason the screen
jumps is a side effect, but it's removed when you only see exactly half the
frames BOB is outputting (IE on a 50Hz TV). On a 100Hz refresh monitor or
TV, every frame will jump, but at a 100 times a second, it probably isn't
very noticeable.

Sorry for the long babble, only just worked it out...

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of James Buckley
Sent: 02 June 2006 17:07
To: 'Discussion about mythtv'
Subject: Re: [mythtv-users] Having problems / Need info on BOB Deinterlacing

Worked out what causes the jitter, it's when you have a mismatches refresh
rate. Originally I was using a 60Hz refresh rate on my TV, and when watching
a BOB deinterlaced stream (which was originally 50Hz interlaced), the video
is jumpy, right? Well I managed to generate a 50.05Hz modeline for my TV,
and now the stream only jumps (as it's too slow for a jitter) about once
every 2 seconds (I.E. Up and down in two seconds), and looks much better to
the eye.

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of James Buckley
Sent: 01 June 2006 12:15
To: 'Discussion about mythtv'
Subject: Re: [mythtv-users] Having problems / Need info on BOB Deinterlacing

The "press the red button" images are also jumpy, I wonder how SKY handles
deinterlacing...

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Dan Seddon
Sent: 01 June 2006 11:46
To: Discussion about mythtv
Subject: Re: [mythtv-users] Having problems / Need info on BOB Deinterlacing


> 2. The OSD goes horrible, hard to describe, but you no what I'm talking
> about
I think you're referring to the vertical jitter, which is kind of due to 
the OSD going over top of a frame which moves up and down by one field 
ever frame and is then interpolated out - the only way round this I've 
found is to make the "detail" in OSD quite a bit larger than one field. 
I have my fonts and other such things on the "bulkiest" settings I can 
and no longer notice these artifacts personally. I guess for this not to 
happen things like the OSD would have to be overlaid after the 
deinterlacing process - I thought this might be the case with XvMC where 
the card plays some part in the decoding, but it made no difference.

Dan
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