[mythtv-users] Is an AMD Athlon 2800+ with MX440 video powerful
enough for DVB HDTV?
craigread at csi.com
Mon May 2 04:36:41 UTC 2005
I'm hoping somebody can give some advice on how to resolve some problems
I've recently had an antenna guy come out with $8k worth of equipment to
try and resolve signal problems at my house. He's relocated the
antenna, checked the signal strength and ber and said that everything is
now well within the threshhold for any HDTV capable device to correct
any errors that are there.
The problem is, I still have errors on 1 SD channel and HD channels are
still unwatchable. When I showed him the picture on my MythTV box, he
said the only thing he could think of was that the machine isn't
powerful enough to handle the error correction on the signal coming in.
Looking at the HD picture on Channel 7 (I'm in Australia), I'd have to
agree. There are very few audio and video artifacts, but the video is
choppy. The one SD channel that breaks up (channel 9) does have
So I've gone through increasing the priority of mythbackend (modifying
the 'NICE=' line in the '/etc/init.d/mythtv-backend' script) and doing
'chmod a+s' on all of the mythtv related programs.
When watching live TV from the remote front end and viewing the output
from top running on the backend, I'm getting 94.4-95% idle when watching
live TV on channel 2 (one of my best channels). I get the same on
channel 9 (even though there are artifacts) and the same on channel 70
(channel 7's HD channel) even though the video is a little choppy.
When watching live TV from the backend and viewing the output from top
running on the backend, I'm getting 73-74% idle when watching live TV
from the backend on channel 2 (one of my best channels). I get 70-72%
idle on channel 9 (even though there are artifacts) and 76-77% idle on
channel 70 (channel 7's HD channel).
One thing I have noticed is the HD channel is less choppy on the remote
front end than on the system doing the recording. The remote front end
is a Duron 1Ghz with a GeForce FX5200, the back end is an Athlon 2800+
with MX440 on-board video. The back end has two Twinhan VisionPlus
Another thing I noticed, is when watching TV on the backend, XFree86 CPU
usage jumps to 3.7% and memory usage jumps to 10% (on 512MB system).
The mythbackend and mythfrontend rarely registers for any real CPU usage
(staying around 0.3% at all times).
So, is the solution to purchase a GF FX5200 to go in the back-end? And
is it possible to give more priority to the error correction of the DVB
stream? I only use the box for MythTV so I'm not fussed if it's sitting
at 50% CPU when watching and/or recording TV, provided it's watchable.
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