[mythtv-users] Remote Mythfrontend Problem

[Ben Coleman]

Steve Milner wrote:
> 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
> _______________________________________________
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> mythtv-users at mythtv.org
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Steve,

This may or may not help.

I had similar problems as you've explained but I came from a different 
set of circumstances. I thought it would be worth sharing anyway ... as 
it might point you somewhere else.

I had a similar setup with separate backend/frontend and my motherboard 
died. I replaced the motherboard but left the original installation of 
myth 0.20 and an older debian.

What I found was that I could not enable DMA on the disks and the disks 
could not handle the information as the drivers that were loaded weren't 
corresponding to the new motherboard. The motherboard was too new for 
the debian install I had.

I installed a new debian release and mythtv 0.21 and those exact issues 
you were describing went away. Now I was assuming that not being able to 
turn DMA on for the HD's was the issue as moving files between PCs was 
an absolute drain on the  PC without it and would drag the PC down to a 
stnadstill ... and that was at 100mbit!!!

I now run it at Gbit with 4 HD tuners and no issues. My signal strength 
is 16%!

Something to think about .. !


Regards,


BC.