[mythtv-users] dropped frames on wlan access.

Jason Ferrara jason at discordia.org
Mon Jan 19 09:17:54 EST 2004

On Jan 19, 2004, at 2:47 AM, Simon at the Threshold wrote:

> Jason Ferrara wrote:
>> My mythtv box is a Dell Dimension 4500 (2Ghz P4) with a Hauppage 
>> WinTV 401 tuner card and a
>> Prism 2.5 based wireless lan card. If there is any heavy network 
>> activity (like copying a file
>> with scp), mythtv will end up with LOTS of dropped frames in the 
>> recording.
>> Does anyone have any idea how to fix this? I'd like to set up a 
>> remote front end, but can't if
>> network activity is going to mess up recording on the back end. I 
>> tried increasing the priority
>> of mythbackend, but that didn't help.
> Interesting, what's the bandwidth on the wlan card BTW?

Its an 802.11b card. I typically get about 500Kbytes/sec transfer 
rates. The other end of the
link is a floor above and on the other side of the house, so there are 
a few walls in the way.

> Well the thing to wach with the ssh package is its very CPU intensive, 
> so your probably better of reducing the priority of your scp process 
> than raising that of mythtv. Try testing scp by running at nice -n 18.

I looked a little more carefully. ssh itself isn't using up the cpu, 
but the system cpu time
shoots way up (to around 60%, with mythbackend and shh using up the 
rest) and the idle time
drops to zero. So I guess the prism2_pci driver is using up all the cpu?

I tried nicing ssh anyway and it didn't make a difference.

> Otherthan that you could simply be running out of ethernet bandwidth, 
> ethernet (802) starts to degrade at 20 percent and baddly at 40% mark. 
> So if you have a 10mbit network (10485760/8 = 1310720 bytes or 1280k 
> per second) 40 percent of that is only 512k (20% is only 256k per 
> second).

I don't understand how bandwidth could be an issue. mythbackend is 
recording directly to local
disk. The only thing using the network is the file copy (which is some 
random file having nothing
to do with mythtv). So less bandwidth should mean the copy will take 
longer, but shouldn't affect
mythtv's recording.

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