[mythtv-users] MythTV looks grainy on big screen TV

[moogie]

On May 24, 2006, at 6:37 PM, moogie wrote:

>
> MythTV box:
> PVR-350 with straight Comcast coxial connection (No
> set top box, Limited Basic and Expanded Basic
> Service.)
> nVidia FX 5200 with VGA, svideo and DVI
> DVI-HDMI cable connects to
> Sony KDF60WF655 LCD Rear Projection HDTV with HDMI
>
> MythTV has all the channels that I get from Comcast.
> Verified this by comparing channels to a old
> (non-Myth) TV in another room.
>
> Program Guide, Recordings, ... all working fine.
>
> Got the xorg.conf working just right.
> The only Modline reported by xorg log file is used
in
> the xorg.conf:
> Modeline  "1920x1080" 74.250 1920 2008 2052 2200
1080
> 1084 1094 1124 interlace +hsync +vsync
>
> Experimented with nvidia-settings and
> loaded the ".nvidia-settings-rc" in ".xsession"
with:
>    nvidia-settings --load-config-only &
>    startxfce4
>
>
> The video stream and text quality are a bit grainy.
> Not pixelated, not choppy.
> This is true for every channel and on screen
> displays like CNN News Ticker, Myth overlays, etc.
>
> What else can I do to improve this?
>
> This Sony has several inputs:
> The 1st HDMI input is mentioned above => PVR-350
> tuner.
> The 3rd coax input is (also) connected to Comcast
> directly => Sony native tuner.
>
> When you compare the same channel on 1st input and
> 3rd inputs, it is obvious that 1st HDMI input
> channel is grainy.


|  On Wed, 24 May 2006 19:37:25 -0600, "Brian Wood"
<beww at beww.org> wrote:
|  If the Myth overlays are noisy/grainy you may have
a connection  
|  problem, the following relates mostly to cable
signals, but sometimes  
|  noise in them can make the overlays look bad.

|  Check your record profiles. Even when you are
watching live TV you  
|  are "recording". Increasing the bitrate(s) will
improve the video  
|  quality, at the cost of storage space of course.

I increased the bitrate but that did not make much of
a difference
on the Sony KDF60WF655 LCD Rear Projection HDTV.
So I copied one mpg file from /video/recordings to a
Linux and a
Windows PC.  Then I used the VLC client on those PC to
play that file
on both those PCs.  Great results.  Nice, clear
playback.  Not at
all grainy.  So it seems that the grainy playback is
only happening on
my Sony.

|  Make sure your capture card is getting adequate
signal, in other  
|  words you don't have multiple splitters feeding it.
Some folks have  
|  stated here that they believe capture cards require
more signal than  
|  a regular TV set and, while I do not particularly
subscribe to that  
|  idea, there might be something to it, one never
knows :-)

I understand.  I do not have multiple or daisy-chained
splitters.

|  Make sure you have good quality cable feeding your
card, and that the  
|  connectors are properly applied (ie: not crimped
with pliers or your  
|  teeth). Make sure the cables are no longer than
necessary.

Agreed.  I don't have any homemade coax cables.  I
only use coax cables
that I got from the local Comcast office.  Each of
these is about the
right size.  Not extra long, just a few inches longer
than needed.
I even swapped a few of these cables around.  Did not
make any difference.

|  Make sure your capture card has the correct
frequency table (STD, IRC  
|  or HRC) as a slightly mis-tuned channel can be
noisy. I have never  
|  had to get into individually fine-tuning each
channel but some people  
|  have reported here that such action has been
necessary to obtain good  
|  pictures.

I did not do this but I did some random recordings
from different
channels and again the mpg files played just fine on
the other 2 PCs.
The grainy result was still there on the Sony.

|  These are all obvious things, but you'd be
surprised how many people  
|  miss them.

Since the Sony is the only one doing this, I am trying
to change the 
Modeline  "1920x1080" 74.250 1920 2008 2052 2200 1080
1084 1094 1124 interlace +hsync +vsync
to some 720p.  But the only Modline reported by xorg
log file is
this "1920x1080".  In the meantime, I am looking at
the modeline
database in the Myth wiki and trying out the various
720p modelines.

|  While I can tell the difference from my Myth output
and direct analog  
|  cable signals most people can't, as they are very
close. Certainly  
|  there should not be enough degradation in going
through the Myth  
|  system to cause complaints.
|  _______________________________________________

Do you have other suggestions?




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