[mythtv-users] Remote Mythfrontend Problem

[Steve Milner]

Hello all.

After several days of trying to understand this myself I must now ask 
for help.

I have a remote mythfrontend and I am noticing a high level of digital 
artefacts while watching live tv (DVB-T).

There are occasional sound glitches including (high pitched short 
sqeaks) as well as small areas (sometimes very large areas) of the 
screen which fail to update or contain grey.

It seems that when I first start watching a channel then for a minute or 
so there are relatively few problems, but they then get worse. But of 
course that could be just my perceptions.

Sound glitches occur about every minute or so and the small areas of 
picture problems about every 10-20 seconds.

I don't seem to be able to find any correlation between the image 
conditions or the sound conditions compared to the problem happening.

To help you understand this let me give you a little bit of the history.

I have been running a backend and frontend on the same box for many 
years with little problem. There was the odd digital artefact (about 
1/20th of the ones listed above) which I put down to a poor tv aerial 
installation (Typically stations would tune with a signal of between 57% 
to 63%).

I decided to embark upon a project to install a new aerial, move the 
mythtv box next to the other server in the house and get myself a new 
fanless silent pc for the frontend, to have a nice quiet lounge again.

The new aerial is installed and when tuning stations I get signal of 
between 68% to 74% which would indicate a better tv signal.

OK, perhaps I had better describe my kit.

Backend:
Intel Pentium 4 3Ghz Dual Core
uname -a : Linux localhost.localdomain 2.6.18-128.1.16.el5.centos.plus 
#1 SMP Wed Jul 1 13:06:47 EDT 2009 i686 i686 i386 GNU/Linux
Twin USB Avermedia Volar DVB-T ( 
http://www.pcworld.idg.com.au/review/pc_components/avermedia/avertv_dvb-t_volar/219054 
)Graphics
Myth TV Install version : 0.21-209.el5
Graphics : nVidia Corporation NV34 [GeForce FX 5200] (rev a1)
Network : Intel Corporation 82562EZ 10/100 Ethernet Controller (rev 02)

Frontend:
Intel Atom 330 1.6GHz (Quad Core or 2x Dual Core - not sure)
uname -a : Linux localhost.localdomain 2.6.18-128.1.16.el5.centos.plus 
#1 SMP Wed Jul 1 13:01:46 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
Myth Frontend Version : 0.21-209.el5
Graphics : Intel Corporation 82945G/GZ Integrated Graphics Controller 
(rev 02)
Sound : Intel Corporation 82801G (ICH7 Family) High Definition Audio 
Controller (rev 01)
Network : Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express 
Gigabit Ethernet controller (rev 02)

Frontend Setup that may be relevant.

I am using the i810 xorg driver with 915resolution to get my TV (1360 x 
768) to work correctly rather than the intel driver. The intel driver 
will start X but the TV has an annoying "Out of Range" box hopping round 
the screen and the problems still persist even if I persevere.
I have working OpenGL with rendering support and woking xv (tested by 
glxinfo and xvinfo) but XvMC does not seem to be supported with the i810 
driver. The problem exists with no xorg.conf or with an Xorg --configure 
generated one.

To get the network card working correctly I needed to use this kmod: 
kmod-r8168-8.012.00_NAPI-1.el5.elrepo but seems to be working fine now.

The network topology is 100MB through 2x switches and I have been using 
one of these network over the mains plug things that claims to 85MB. I 
have tested this directly with cable and the problem persists but could 
be very marginally better with the cable. I have monitored (using 
gnome-system-monitor) on both the frontend and backend and could see no 
problems on the networking graphs when these artefacts happened.

I can play local DVDs fine (I use Xine).
If I play the recorded content (which is not being streamed directly - 
but using an NFS share) there seem to be no problems, but I haven't 
tested this with my current sound/graphics setup.

Any help, advice, suggestions, further information requests or things to 
test will be gratefully received.

Regards,
Steve