[mythtv-users] Commercial flagging on backend disrupts HDTV playback on front end

Brad DerManouelian myth at dermanouelian.com
Mon Sep 10 20:16:14 UTC 2007

On Sep 10, 2007, at 1:01 PM, Taco Mel wrote:

> With my current settings I have experienced a problem
> with playing back HDTV (prebuffer pauses, very
> jittery) when the back end server is "busy":
> 1. Recording HDTV stream with pcHDTV 5500
> 2. Recording SDTV stream with Hauppauge 500
> 3. Commercial flagging #1 and #2
> 4. Feeding HDTV stream #1 to remote front end
> The back end has 1 TB storage in RAID-5 and is a dual
> Xeon 1.8 GHz setup, hyperthreading enabled.  Linux
> sees this as 4 CPU's.  There I find a "mythcommflag"
> process using 100% of a CPU (iowait around 5-20%).
> The front end (Athlon X2 5200+) isn't even breaking a
> sweat. I tried to "renice" the mythcommflag process to
> +19 on the back end and this did not help.  Killing
> mythcommflag on the back end immediately "fixed" the
> problem.
> While it's easy enough for me to log in to the back
> end to kill the commercial flagging, I'd like
> something more automated and wife-friendly than this.
> If I export the recordings directory via NFS is it
> possible to run the commercial flagging from another
> machine -- perhaps on the aforementioned front end
> which has plenty of free cycles?  Preferably just for
> this one source?  Should I turn off hyperthreading on
> the back end?  Any better ideas?

What kind of bandwidth do you have? You can run a slave backend on  
your frontend machine and only allow commflag jobs, then turn off  
commflag jobs on your master backend so the machine with the cycles  
does all your commflagging. Export to NFS shouldn't be necessary.  
Myth is smart enough to transfer the files via the myth protocol if  
they aren't located locally on the machine (or mounted from another  

Now that I think of it, you probably don't need to run a full slave  
backend on the machine. Just MythJobQueue. More about that here:

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