[mythtv-users] PVR-500 picture quality

Paul Gardiner lists at glidos.net
Mon Feb 1 09:26:59 UTC 2010

Joey Morris wrote:
> I'm new to MythTV, and I've installed a PVR-500 to capture standard
> def programming from my cable company. The picture quality of the
> captured streams appears to be slightly lower than what I see when I
> connect the cable directly to my standard def TV. This is true for the
> card's coax connection (connecting directly from the wall) and for its
> composite and S-Video connections (connecting from the cable box).
> I've made sure the recording resolution is 720x480, I've increased the
> bitrates to 7000/8000, I'm using a G210 card with VDPAU enabled, and
> I've tried using a signal amplifier. I think I may be maxing out my
> PVR-500's performance.
> The quality is certainly tolerable. Although I notice the difference
> when comparing them side-by-side, I'm not sure I would if I viewed the
> card's output in isolation. Is the slight drop in picture quality just
> the nature of analog capture? Those of you using the PVR-500s, do you
> just live with it so you can enjoy the numerous benefits of MythTV? Or
> are there other things I can try to make the picture quality match
> what I see when I connect the cable box directly to the TV? If I
> eventually move to HD, can I expect a similarly slight quality drop
> when using the component output to an HD-PVR?

I'm sure there's some loss in the capture stage, but don't rule out
loss also at the playback stage when dealing with SD under MythTv.
My set up has dvb-t as source, so zero loss on the recording side,
yet it took me ages (and 3 frontend builds) before I achieved
image quality equal to commercial equipment. The trick at playback
is to do as little processing as possible, so:

1 Set up the x screen to match the content 720x480. Scaling from
720x480 to 800x600 will lose quality.

2 Don't adjust the playback window to avoid overscan. Scaling from
720x480 to 71Xx47X will really notice.

3 Don't use bobdeint or linear deinterlacers.

But having said that, in your case, it is possible that you are
losing so much at the capture stage that the above things wont
make any difference. I just know they made a big difference with
my system.


More information about the mythtv-users mailing list