[mythtv] Loud hard drive due to NuppelVideoRecorder.cpp sync()

cmisip cmisip at insightbb.com
Fri Jun 13 14:55:20 EDT 2003


I installed myth .9 and I did notice a slowdown.  The video pauses every
now and then and I get rebufering messages.    I have not timed the
pauses though.  This is why I asked in an earlier post if the system
requirements have increased for .9 because of increased video
choppiness.  The problem is not apparent when there is only one  ongoing
recording.  But if there are two simultaneous recording going on, then
the problem is very apparent and distracting so much so that I reverted
to an earlier CVS version which I downloaded on 5/25/03.  Could these
database writes been introduced after that?  Most mythtv systems are
probably single tuner systems so this problem may not be noticeable to
many unless you have a dual tuner system, or your hard drive is slow to
begin with on a one tuner system.    I am not sure if the problem noted
in this thread may be the same thing.  How might one disable these
writes?  If somebody writes a patch against .9 to do this, I can try it
out and see if the problem disappears.  I have an ATI TV Wonder and ATI
Wonder VE recoring on an LVM ext3 partition with with a total of 260
gigs of space.  Thanks


On Fri, 2003-06-13 at 09:15, Chris Pinkham wrote:
> > One final thought.  Many people seem to have noticed a slow down with
> > version 0.9 (for now I've been sticking with 0.8).  I haven't fiddled with
> > it yet, but I was wonderring if the "position map" database write that
> > occurs every key frame may be the culprit (it comes right after the sync()
> > call in NuppelVideoRecorder.cpp).  There's also the call to the somewhat
> > kludgy looking "KickDatabase" function which I'm not totally sure about...
> > ;)
> 
> The positionMap write only gets done every 15th keyframe which is once every
> 15 seconds and it only writes out the new entries which haven't been written
> yet so it's pretty quick.  I don't notice any problems on my Athlon 700
> recording at 352x480 using mpeg4 and running the backend and the mysql
> server and that's a pretty low-end MythTV box.
> 
> You'll have to ask Isaac about the KickDatabase stuff, that's not my code
> but the "write positionMap every 15 frames" stuff is.
> 
> I haven't noticed any slowdown as 0.8 developed into 0.9 and I try to
> keep synced with CVS.  My under-powered Athlon hasn't started skipping
> frames or anything and I'm doing a pretty good job of pushing it to the
> limit anyway.
> 
> Chris
> 
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