[mythtv-users] Charlie Rose via PVR-350

[Mercury Morris]

On 9/20/05, Mark Knecht <markknecht at gmail.com> wrote:
> 
> On 9/20/05, Mercury Morris <mercury.morris at gmail.com> wrote:
> > On 9/19/05, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> > > Could this be a problem with your system (instead of a problem with
> > > Myth) that others are seeing where running mythfilldatabase (or wget 
> of
> > > any kind) while recording causes an IOBOUND situation that prevents
> > > information from being written properly and causes an A/V sync offset?
> > > In other words, does Charlie Rose happen to record around the time 
> your
> > > mythfilldatabase runs?
> > >
> > >
> > http://www.gossamer-threads.com/lists/mythtv/commits/150176
> >
> > Yes Mike ! In the mythbackend.log, there are IOBOUND entries that
> > correspond in time exactly! to the discontinuities in the Charlie Rose
> > show.
> >
> > But here's the thing: I had already suspected mythfilldatabase because
> > it had been running within the Charlie Rose hour. So, I changed the
> > window for mythfilldatabase to run outside of that hour - problem still
> > occurred.
> 
> Did you completely restart the backend mysql processes after doing
> this? Maybe even reboot to be sure?


Yes. After changing the mythfilldatabase window, I waited until two
days had passed. During those two days, the system did its normal
shutdown-and-wakeup thing. That is, it shutdown the computer and
re-booted at the times when programs were scheduled to be recorded.

>
> > So, mythfilldatabase is not the cause, BUT the system is recording
> > Letterman (in HDTV) from an HD3000 card at the same time.
> > I guess that the simultaneous recordings are too much for the I/O
> > system to handle - a bit of a surprise to me.
> 
> Not likely unless you have no DMA on your hard drives or the data is
> traversing the network. My backend storage is not on my backend
> server. I never see problems like this but I don't record HD either.
> None the less that should be less than 5MB/S which even a non-DMA hard
> drive might keep up with...


Yeah, that's what I thought ! How could the I/O system of newly-built
computer be unable to keep up with only two write-to-disk tasks. I've
watched the disk-activity light (not a good measure of load, I know),
and it blinks slowly. It's nothing like when the system is running updatedb
or makewhatis. 

>
> > But now, thanks to you pointing me to the logs, I can set up the
> > recording schedules so that only one recording takes place at a time.
> > (Of course, I feel that I should have looked in the logs without having
> > to be told to.)
> >
> > One more observation, about a specific time: Last night's out-of-sync
> > break occurred at 36:19 into the Charlie Rose show. That's within the
> > first two minutes of Letterman. Maybe there is extra overhead at the 
> start
> > of a recording?
> 
> Possibly.


If there is a problem with starting a second recording when a first 
recording
is underway, then it should be repeatable. I may set up some tests that
run during Daytime TV, to see if I can get the out-of-sync problem to
repeat, reliably.

-- 
MM
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