[mythtv-users] Questionable capture quality from a PVR-250
papenfuss at juneau.me.vt.edu
papenfuss at juneau.me.vt.edu
Thu Feb 5 07:21:45 EST 2004
I felt the need to jump in this thread somewhere and clarify a few
things, as it wounds like the original poster is seeing the same things I am.
> >
> > 1. Is it actually possible to get captured video with a PVR-250 that
> > rivals/exceeds the output from my TV's tuner?
> Probably depends on the TV's tuner.
>
> In my case, I can say *yes*, but dependent on the input signal. I've mentioned
> before I use OTA broadcast. Some channels have good quality, some channels are
> crap.
I'd believe this, but I'm sure if I were to watch it on a
crappy-quality tv I wouldn't even notice any quality problems (not that I'm
acusing you of having a crappy tv!). I haven't noticed any difference between
channels.
>
> The PVR-x50 (and every PC-based tuner I have ever tried) does NOT deal well with
> high amounts of noise being recorded. My 350 absolutely hates WWOR and WPIX out
> of NYC, but those are extremely noisy channels. ONLY my Panasonic VCR feeding
> the downstairs 27" TV does well on these signals. Every PC-based tuner I've
> used hates these particular channels, so does every other TV in the house. :)
>
> In the case of WNBC 4 out of NYC, where the signal quality is excellent, my 350
> with light application of DNR (dnr_mode=3, dnr_spatial=6, dnr_temporal=12), the
> quality exceeds watching TV directly when tuned via a Panasonic VCR if I burn
> the video to DVD and play it back using a Rowa DVD-3610.
>
I thought about the noise issue, and played with the dnr_* settings on
mine. The best description I can come up with to describe the difference
between the TV tuner and the PVR-250 is that the TV has slightly more noise,
but a sharper picture. The PVR-250's filters out the noise, but loses
luminance sharpness (even tried this in B&W BTW). It's almost exactly like the
dnr_spatial is set to some midrange value (even when it's set to zero or
dnr_mod off). I can make the picture worse (softer) by cranking up the
dnr_spatial.
> You mention that your quality is good when using xine to play DVDs- have you
> tried playing back the recorded MPEG using xine?
>
Although I use mplayer, that's what I did when I tweaked the dnr_*
settings. The playback results were the same as with mythtv.
> Also, you may or may not need to manually tweak the
> brightness/contrast/finetune/etc. per channel. (On most channels I do. On WNBC
> I run the defaults.)
The color saturation/etc is much better on the PVR than the POS bttv
card I've also got in the system, but nothing (I've found at least) can improve
the sharpness.
>
> > 3. Is it possible that my card just isn't very good?
> Maybe.
>
DOH!
> As to my recording settings:
> 720x480, DVD stream type, 7000 kbps avg bitrate, 7900 max bitrate. See above
> dnr settings for WNBC. (Tweak these as appropriate.)
>
As I've mentioned before, anything over 352x480 (or at best 400x480) is
wasted on my card/setup. I cannot distinguish any quality difference (even
with bitrate >8000 kbps).
Argh...
-Cory
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