[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
-- 
*************************************************************************
* The prime directive of Linux:  					*
* 	- learn what you don't know, 					*
* 	- teach what you do.						*
* 						(Just my 20 USm$)	*
*************************************************************************




More information about the mythtv-users mailing list