[mythtv-users] Need help trying to nail down some picture quality issues

DTR dtr at edenforge.com
Mon Aug 30 14:02:59 EDT 2004

Thanks for the great info, I gave this a try and it's definitely a step 
in the right direction.   So far I haven't noticed nearly as many 
shimmery artifacts.

Something interesting I noticed... when I set my X desktop to 640x480 
and my recording size to 640x480,  I kept getting these "glitch" frames 
every minute or so.  I turned the recording res up a bit and this seemed 
to disappear.  Not sure what would cause this but it was almost like it 
was "starved" for video stream data.

One question about your use of quickdnr over denoise3d.  Was that purely 
for CPU economics or do you think that quickdnr provides superior 
results in this case?   The reason I ask is that my cpu is on the fast 
side so it wouldn't be an issue to go with denoise3d if that would 
provide a slightly better picture.



Bruce Markey wrote:

> DTR wrote:
>> I'm having some picture quality issues.  Watching the olympics, when I 
>> see a shot of the track with the white lane lines running diagonally 
>> across the screen, the lines seem to shimmer and squirm around.
>> I've looked thru the archives and closest I've found is mention of 
>> jaggies... it's not so much the jagged edge that bothers me as how 
>> they kind of dance around.  I'm not sure if this is the sort of 
>> artifact people are referring to when they say "jaggies".
>> I've tried running kerneldeint and denoise3d with default parameters 
>> which didn't seem to make a difference.
>> Here is my info:
>> PVR250
>> MX-440 TV out
>> recording at 720x480
>> kerneldeint, denoise3d
>> xvmc disabled
> Try this. If you are using the nvidia 4363 driver, set
>        Driver          "nvidia"
>        Option          "TVOverScan" "0.979"
> in your XF86Config-4 file and set the display size to 640x480
> then restart X. If you are using 6111, still set the size to
> 640x489 and run nvidia-settings and set TVOverScan to "250".
> This will probably be too big for your TV screen and push stuff
> off the edge but these settings will do a better job if lining
> up the scanlines in the recording with the scanlines on the TV
> This should correct most of the jagged edges of the diagonal
> white lines. It should also significantly reduce (but not
> eliminate) interlace artifacts.
> As for the shimmering, if you press Pause then right arrow
> you will step through frames one at a time, you will see that
> the white line has a rainbow of colors around the edges. Each
> frame has a different combination of colors. Played at normal
> speed, it looks white but shimmering. The kerneldeint filter
> actually seems to exaggerate this effect. Even though I'm the
> fool ;-) who wrote in the docs that kerneldeint and denoise3d
> are a good choice for good deinterlace and noise reduction,
> I now use the alignment trick above and longer use kerneldeint.
> This reduces the shimmer a lot. I also use "quickdnr=0:20" in
> place of denoise3d. This uses a little less CPU and the args
> are geared to dampen small variations in color.
> With these settings I've almost forgotten that I'd had this
> annoying shimmer in the past ;-).
> --  bjm
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