[mythtv-users] Video Quality

[mythtv at brtb.org]

Umm...

Something's wrong with your setup if that's all an Athlon 1800 can do...
my Athlon 1700 will do 640x480 mpeg4 (bare, no 4MV/high-quality) record
and deinterlaced playback at the same time with about 85-95% processor
usage. Mostly defaults on the tweaks side... standard 266mhz fsb, no
overclocking, it's pc3200 memory but only running at pc2100 speed, hdparm
is already configured for optimum settings when I boot. X is at 1024x768
on a Radeon 7500 (default X drivers, GATOS ones don't do the colorspace
conversion right). That may be an area for you to look at - I had an
Nvidia TNT2 in here and it didn't accelerate XV operations nearly as
well, always had the processor pegged at 100%.

Actually, I seem to remember the P3-667 being able to record 640x480
mpeg4, just not playback at the same time. Might have been just 480x480,
but still.

Next up: PVR250 rev3. Mostly for the enhanced quality (my old Model 401
WinTV-fm has serious interference issues) but the mpeg2 is a plus... just
got the DVD burner too. =]

-- brtb


On Thu, 11 Mar 2004, Jared Luxenberg wrote:

> You're able to capture at 640x480 on an Athlong 1GHz?  I have an Athlon XP
> 1800+ and it can barely do MPEG4 at 480x480 with no filters.  Are there any
> performance tweaks you did, or maybe something I'm doing wrong?
>
> - Jared
>
> -----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 12:29 PM
> To: 'Discussion about mythtv'
> Subject: RE: [mythtv-users] Video Quality
>
>
>
> > Hello,
> >
> > I am in the process of ironing out a few kinks with my mythtv
> > but I was wondering about what type of quality people are
> > experiencing with their recordings off of digital cable/cable
> > TV. I'm using an Osprey 200, an entry level video card.
> >
> > How much of a video quality upgrade does one get by moving
> > from a basic card like that to one of the PVR cards like the
> > Hauppauge PVR 350. For example does the on board Mpeg 2 make
> > that much of a difference? After all can't one just compress
> > the signal after capture (sacrificing time and HD space for
> > $$$) or is there more to it than that.
> >
> > Perhaps people could post samples of video captured. I don't
> > want to get anyone in trouble - maybe they could just post
> > something off of public TV etc... I just want to get a sense
> > of the quality. For example Tivo's high quality setting looks
> > to my eye exactly like the broadcast signal coming in
> > - there are no artifacts on a TV.  Is this possible with a
> > Linux PVR rig? Also is it only possible with the higher end
> > capture cards?
> >
> > Personally I probably won't want to use mythtv to actually
> > watch my recordings. I'm perfectly content saving them to
> > DVD-R and watching them on my DVD player. I'm just wondering
> > if that will look as good as the original broadcast or will
> > it look strange. How successful is mythtv as a digital VCR?
> >
>
> First principle:  No matter what hardware/software you use,
> capture (frame grab) can be perfect for all practical purposes
> but the compress-uncompress process involves some loss (assuming
> no use of lossless codecs like huffyuv).
>
> The key elements are avoiding unecessary loss due to poor
> cable signals, poor tuner quality, poor video processing/
> digitizing, etc., then looking for compression methods that
> keep signal loss and artifacts as un-noticable as possible
> on your display device.
>
> 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."
>
> It would be interesting to hear how hardware MPEG-2 compares
> with MPEG-4 in a system without my CPU limitations.  I can't go
> beyond the settings listed above with my 1 GHz Athlon.
> >
>
>
>