[mythtv-users] Re: Need advice with 'Pixelization"

[Joe Votour]

I see the same pixelization, and I'm capturing at
720x480, with a bitrate between 5000 and 6500.

I'm inclined to believe that it's the MPEG-2 generated
by the PVR-250 that is the cause, but my knowledge of
MPEG-2 isn't enough for me to even begin to offer an
explanation.

The only thing that I can think of is that there's so
much movement (or change) in the scene, that the delta
frame (I forget what letter it is called, but it's
definitely not the I-frame) ends up with the
blockiness.

In my case though, the cable TV coax coming into my
apartment is pretty crappy (there's ingress according
to the Comcast tech, but it's my landlord responsible
for the line, not Comcast, so I have to live with it).
 I haven't brought the RF analyzer home from work yet,
but I know that my signal is around 30dBmV, which is
on the crap side.  I get some artifacts in MythTV, and
occasionally, if I watch something on the TV (not in
Myth), I end up with a "staticy" (is that even a
word?) picture, or wavy lines in it.  I also get the
odd dropped frame.  I attribute the blockiness to
these factors (in my case, anyway).

-- Joe

--- Ian Trider <iantri at gmail.com> wrote:
> AFAIK, the MythTV defaults for bitrate are way too
> low.  You need (if
> recording at 480x480) roughly 5000kbit/s for a good
> image.
> 
> Also, you might be seeing interlacing artefacts if
> you are playing
> back on a computer monitor/standard video card
> graphics out and aren't
> deinterlacing -- make sure "Deinterlace playback" is
> enabled in the
> settings.
> 
> 
> On 4/13/05, Larry K <lunchtimelarry at gmail.com>
> wrote:
> > Let me add that I am not doing HD, and I am taking
> all the mythtv defaults
> > for bitrates, etc.
> > 
> > 
> > On 4/13/05, Larry K < lunchtimelarry at gmail.com>
> wrote:
> > > I'm somewhat perplexed, so I figured I'd post
> here and see if anyone has
> > solved this issue already.  A search of the
> database does not produce
> > anything that looks like what I am seeing.
> > > 
> > > In brief, I have the following system:
> > > 
> > > Athlon 2500
> > > 256MB RAM
> > > 160GB DMA HD
> > > PVR-250
> > > 
> > > I have only had the system working for about a
> week, but already I notice
> > that when I watch live TV, or play back a
> recording, I notice areas of what
> > I call "pixelization" where there is sudden or
> significant movement in the
> > image.  The image does not stutter or act jerky,
> to the extent that the
> > entire image does not seem affected by this issue.
>  The problem appears in
> > isolated areas, and then as the motion in that
> ares of the image subsides,
> > the pixelization subsides as well.  If I had to
> guess, it's almost as if the
> > PVR could not encode the movement sufficiently to
> make it appear smooth
> > during playback.  
> > > 
> > > Does anyone have any thoughts as to what might
> cause this?
> > > 
> > > Thanks,
> > > Larry
> > > 
> > > 
> > 
> >  
> > _______________________________________________
> > mythtv-users mailing list
> > mythtv-users at mythtv.org
> >
>
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > 
> > 
> > 
> 
> 
> -- 
> Ian Trider
> iantri at gmail.com
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
>
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> 


		
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