[mythtv-users] mpeg2 playback quality captured with PVR-150

Brian Wood beww at beww.org
Fri Oct 5 23:30:30 UTC 2007


Chandi Bernier wrote:
>  
> Hi,
> 
> I've got a bad quality when watching stuff recorded from my PVR-150.
> 
> On some channels I've got diagonal lines but that seems to come from my
> cable signal which would be too low for the capture card.
> 
> But on all channels, the picture is not as sharp as regular TV and has a
> lot of artifacts. Those are mostly moire (colors appearing where there
> shouldn't be), the picture is a little bit flickering and solid colors
> are not solid anymore, we can see noise on them.
> 
> I've been trying many different configs today but none of them was
> acceptable enough to watch live TV.
> 
> My display resolution is 640x480 through DVI but I've also tried
> 1280x720, 720x480. My TV is an HDTV CRT from toshiba (26HF85C)
> 
> I've adjusted the capture resolution to 640x480 but it doesn't seem to
> make a difference.
> 
> The bitrate is 7500/9000 but that also doesn't really make a difference.
> 
> I've tried many different filters settings like quickdnr with numbers
> ranging from 0 to 255.
> 
> I've also tried denoise3d with many different settings. While my CPU was
> too slow to play smoothly, I could at least see that the picture came
> out with more "vertical rectangles" artifacts.
> 
> Playbacks settings are as such :
> Deinterlaced with Kernel
> Preferred mpeg2 decoder : standard
> Enabled OpenGL vertical sync
> Video as timebase
> extra audio buffering
> 
> But I've been playing all day long with those settings only to notice
> subtle changes in quality but nothing comparable to Regular TV.
> 
> I've also tried to play with v4l2-ctl settings for the capture card
> (spatial noise filter, temporal, etc) without any success.
> 
> My back/frontend is a P3-1000 with 512mb Nvidia 5500 card and I'm using
> Nvidia's drivers
> Needless to say that the picture quality with menus, Divx and everything
> else is perfect.
> 
> Is anybody else suffering from the same problems ?
> Has anybody been able to fix that ?


My 150-captured video looks pretty good. A very careful analysis will
show the MPEG artifacts, but a casual viewer would probably not see them.

Sounds like at least some of your problems are with your cable feed, do
what you can to fix those.

Then, try and discover if the problems you see are with the recording or
the playback. Try getting some test MPEG files that are known to be good
and see what they look like.

A noisy signal will often require a higher bitrate, and even then the
problems can be enhanced.

beww



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