[mythtv-users] backend takes 100% CPU recording DVB-T

Nick Craig-Wood nick at craig-wood.com
Mon Apr 17 08:51:08 UTC 2006

On Thu, Apr 13, 2006 at 09:35:28AM +0100, Stephen Williams wrote:
> On 4/1/06, Chris Hubball <chris at hubball.org> wrote:
> > I'm running 0.19 and I'm finding that the backend is taking 100% when
> > recording DVB-T from my Nova-T card.
> >
> > This makes Live TV impossible because it has no CPU time left for playback.
> >
> > I would expect the backend to only take a small amount of CPU time
> > because it's basically just saving the MPEG-2 stream to a file.
> >
> > I'm thinking that maybe there is some transcoding going on, however I
> > think I've disabled all transcode options.
> >
> > Does anyone out there have a Nova-T running with a reasonable CPU usage?
> Ran into this problem last night also with a Nova-T (old 909 model).
> Now the really interesting thing is that this only started happening
> for me when testing kernel 2.6.15 (Debian testing branch). Running the
> _same_ 0.19 install (from source against the fixes branch) and
> configuration with a 2.6.8 kernel results in the normal (very low) CPU
> usage. Switching to 2.6.15 results in 100% CPU usage and an unusable
> system during recordings.
> So it appears that the problem isn't exclusively linked to 0.19, maybe
> this is an interaction between myth 0.19 and recent versions of the
> Nova-T driver, or maybe it's only a driver issue.
> My question to everybody else who is seeing this problem is what
> version of the DVB drivers and kernel are you using?

I have a similar setup with mythtv 0.19-0.6 (from marillat), debian
testing and kernel (debian) 2.6.15-1-686, a 1.7GHz P4 and two of the
original nova-t cards.

I've found that CPU seems to average about 30% while recording (using
top -d 30) for one channel.  However the CPU usage does spike up to
100% for 5 seconds at a time.

I haven't been able to make LiveTV work since upgrading to 0.19 though
- I just get a timeout after about 40s.

0.19 has been recording stuff just fine.

Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick

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