[mythtv-users] Playback vid corruption with HD NBC (1080i oramd64 related?)

gad at jetcom.org gad at jetcom.org
Wed Jun 15 14:38:25 UTC 2005

Hmm. looking at the guide, i found this:

Some people have run into issues with their cards generating a slight 
inverse ghosted image off to the right of the main picture, myself 
included. The recommended fix, which appears to be working for me, is 
to set the DNR mode to 0 (mine was initially set to 3), like this:
# /usr/bin/ivtvctl -c dnr_mode=0

Also make sure that the values for DNR temporal and spatial filters are 
set to 0, for best results:
# /usr/bin/ivtvctl -c dnr_temporal=0
# /usr/bin/ivtvctl -c dnr_spatial=0 However, it seems to be pvr350 
output related. I don't have a pvr 350 in here. I am using a 350 for 
recording in a different backend, but I see this effect on low-def 
stuff recorded both with the pvr, and the low-def DTV signal I get from 
my CBS affiliate. Quoting Todd Bailey <toddb at toddbailey.net>:
> I remember reading something about this in Wilson's install guide.  
> you might want to check and see if various forms of filtering is 
> turned off.
> spatial and dnr come to mind

>> Quoting Ian Trider <iantri at gmail.com>:
>>>> This is different than the problem that I have with the bob deint. With
>>>> that the  SD stuff will shimmer. I haven't seen a fix for that one
>>>> either.  I believe that is also amd64 related.
>>> I don't know about the main problem you describe in your message, but
>>> what you describe here is pretty much inherent in a bob deinterlace --
>>> it takes each field of the original interlaced frame and blows it up
>>> to full size, then plays the two one after another in time.
>>> Because the two interlaced fields are in slightly different spatial
>>> positions (i.e. the first field covers the odd scanlines, second field
>>> covers the even scanlines) the image will wobble/jitter vertically
>>> slightly. (That's why it's called 'bob' <g>)
>>> There are strategies for reducing this, but I'm don't know if myth
>>> implements them (using PVR-350 for output) -- if it is available for
>>> realtime playback, though, kerneldeint should look nice, but the
>>> motion won't be as 'smooth'.
>>> I'm guessing this isn't really noticable in HD material because the
>>> higher-resolution probably covers up for the bob effect.
>> Comparing bob on a x86 machine to it on a amd64 machine. There is 
>> definately something wrong with the amd64.  Shimmer was a bad word, 
>> it's more like double vision or ghosting. It did not used to look 
>> like this.
>> Is there a way to take screen shots in myth?  I'd love to provide 
>> pictures of these effects.

More information about the mythtv-users mailing list