[mythtv-users] Video Quality

Adam Biskobing tv at badmoon.com
Thu Mar 11 16:54:37 EST 2004


It is also very dependant on the signal coming in.  Originally I had my
PVR-250 connected to a coax cable connection.  When I moved I got
DirecTV and connected up via an s-video cable, and my picture
dramatically improved.  My MythTV box now looks better than my Tivo.

> -----Original Message-----
> From: mythtv-users-bounces at mythtv.org 
> [mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Alan Snyder
> Sent: Thursday, March 11, 2004 3:17 PM
> To: 'Discussion about mythtv'
> Subject: RE: [mythtv-users] Video Quality
> 
> 
> > > 
> > > With a dirt-cheap bt878 capture card, generic
> > > GEForce-2 video card, and mid-90's 27" TV, with myth doing
> > MPEG-4 at
> > > 640x480, 2200kbps, the difference between live TV through myth and
> > > live TV off the cable is noticable but not bothersome.  The CNN 
> > > "crawl" is a little jumpy.  There's some loss of detail in the 
> > > highlights (I think that might be a bt878 chipset issue). 
>  Up close 
> > > (closer than I watch), some blockiness is present 
> > (replacing the less
> > > noticable noise in an analog picture).  Football can seem 
> harder to
> > > follow, probably because of the limitations of the compression 
> > > settings to handle the frame-to-frame changes in content.  But 
> > > overall, the difference is similar to the difference 
> between a good 
> > > cable signal and an "OK" cable signal.  I do notice that 
> for certain
> > > channels where the cable signal is weaker, the noise in the 
> > > original results in more artifacts in the processed video.
> > > This is most likely because the compression scheme needs to
> > > deal with all that extra "information."
> > 
> > Before I go through and do this I need to be clear on this
> > one- is watching sports not very good through mythtv?  If I 
> > am watching hockey or football on a large TV, having the 
> > ability to pause live TV would cause large amounts of 
> > distortion?  How noticeable is the difference between a 
> > recording and live TV when watching sports?  Thanks for any 
> > information.
> 
> Since I posted this, I should respond.  My expectation is 
> that if I had a faster CPU and could go to the 3000kbps 
> range, these artifacts of the compression scheme would go 
> away.  At some point, the difference between the original and 
> the compressed copy becomes indistinguishable.
> 
> People who have PVR-250's can tell you whether the card 
> essentially gets to the quality of a well-encoded DVD movie.  
> I would *guess* that it can.  I also expect from my 
> experience with my 1 GHz system that a 2 GHz system would 
> probably make my results indistinguishable from the original.
> 
> Others have pointed out one (probably not the only one :)) 
> shortcoming of my original comments:  The filters provide an 
> opportunity to
> *improve* the picture.  You cannot recover lost information.  But 
> that doesn't mean that certain filters won't make it *look* 
> better than the original.
> 
> 



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