[mythtv-users] PVR250 Settings?

[papenfuss at juneau.me.vt.edu]

> Cory,
> 
> I've been pretty confused by this whole size/bitrate issue for a while.

	Probably part of it is the "normalized" bitrate that is default for 
mythtv.  I think it tried to be a good idea, but there are too many variables 
to compare one person's setup to another with just a bitrate/resolution 
normalization.  This is especially true regarding all the rampant confusion 
regarding "lines of resolution" being 240/330/480/720/etc/etc.  

> Like you, I've been a tiny bit annoyed at a slight loss of video quality
> compared to direct-from-digital-cable-box or even compared to my TiVo.  (I'm
> probably being somewhat anal-retentive about this --- no one else in my
> family really notices the difference unless I ask them to look really
> hard...).  I'm also using a pvr-250 for capture, and would say that my
> capture quality is very similar to yours.

	Just for grins, is yours a rev1 pvr250?  There's some suspicion that 
it's on the rev1's.

> 
> At the moment I am capturing at 352x480, with a bitrate of 6000.  I've tried
> higher resolutions, all the way up to 720x480, but frankly see no
> difference, and in fact sometimes the image gets worse unless I am also
> increasing the bitrate at the same time.  (I'm viewing on a 42" hdtv plasma
> monitor.)  When I keep the resolution constant and then vary bitrate from,
> say, 1800 up to 6000, I get a sharper (even somewhat brighter-looking)
> image, though not dramatically so.  In your samples, for instance, I see a
> very slight improvement as you move from your 2.5/4.5Mbps bitrate sample up
> to the 8.0/10.0 Mbps bitrate sample, particularly in the lighting detail in
> the background trees and leaves.  So I see definite improvement with
> increased bitrate, but it is really marginal.

	Even with my softness, I can see a slight loss of sharpness at 352x480.  
I'm torn between encoding at that DVD-friendly resolution and the more adequate 
but non DVD-friendly resolution of 480x480.  I did notice a very slight 
improvement in my still image captures at higher bitrates, but nothing that 
really helped with the soft picture.  

> 
> Others (notably Jarod) have observed image quality that is on-par with
> direct-from-cable.  I get that with my TiVo, so I know it is possible.  But
> I'm just not getting that right now with my Mythbox.  For a while I was
> blaming my video card (GF4MX440, using vga output direct to plasma monitor),
> but dvd's played via xine look stunningly good, so it seems to me that the
> video card is blameless, and that the captured video is itself inferior in
> quality.  I've also tried the experiment of copying some of the mpeg files
> to my G5 Mac with cinema display, and again I see inferior quality when
> compared with the EyeTV unit on that Mac.
> 
	I, too, am sure that it's not the TVOUT, as divx's and DVD's look 
great.  Looks like a simple loss of high-frequencies to me.... I might even 
try recording my test signal and see what that does.  I rigged one up that can 
acutually generate about 1200 analog lines of resolution.

> My conclusion, then, is that somehow I may have an inferior pvr-250 card.
> I'm planning to add a second card to my mythbox within the next couple of
> weeks, and so perhaps I'll see different capture quality with the new card.

	I'm suspect, too, thus the request for more sample clips from people.
> 
> Or maybe everyone else is fooling themselves into believing that their
> capture quality is better than it really is (though I doubt it... ;-)

	Me too... most people on this list are much more insane about their 
setup than I am... :)

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