[mythtv-users] Jerky panning all cards and resolutions. Thoughts on where to look?
ignasiak at gmail.com
Wed Jun 13 16:06:09 UTC 2007
On 5/26/07, William Munson <william_munson at bellsouth.net> wrote:
> Ben Lancaster wrote:
> >> Since day one I have noticed that panning scenes have a distinct
> >> "gallop". This is independent of video mode, resolution, signal source,
> >> real time setting or rendering method. On about a 1/2 to 1 second cycle
> >> the pan will speed up and slow down in a repeating pattern. Nothing I
> >> have tried has fixed the problem. I dont think this is related to cpu
> >> usage as it happens even when playing SD which results in an average
> >> usage of about 12%. HD playback is 50-55% usage. The box is a dedicated
> >> myth system with a 2.8GHz AthlonXP mobile with plenty of memory. Signal
> >> sources are 2 pvr-250's and a HDHR. Video card is a NVidia FX5200 using
> >> the standard VGA output to drive my HD monitor. This has happened since
> >> myth 0.19 and is present in 0.20, 0.20.1 and SVN so I doubt its myth
> >> itself. Any suggestions on what else to check?
> > Are you by any chance watching 50Hz/25Hz source over 60Hz VGA? If you're
> > in the UK/Australia then this is probably the case - the problem is
> > caused by mythtv's framerate interpolation (adding the extra 10 frames
> > to make it up to 60) as it would seem it just duplicates frames, hence
> > the jerkiness
> > The only solution is to go for DVI->HDMI and set it to 50Hz. I tried
> > component on my Nvidia 6200 card, but from what I read Nvidia have
> > "locked" the component output to 60Hz, so you get the same problem.
> > Very annoying, I know. This is one thing that MCE has over MythTV - 50Hz
> > video plays flawlessly smooth over a 60Hz link!
> Replying to my own message. I finally found out what caused my jerky
> video issues. It turned out to be my storage method. I was running a
> LVM on a pair of IDE drives and a SATA drive using XFS on top of the
> LVM. I removed the LVM and converted back to three XFS formatted
> partitions and used the storage directory feature in SVN with two of
> the partitions. Now it plays as smooth as butter and almost all of the
> video break-up is gone. The breakups that are left appear to be from my
> crappy ComCrap cable service. I suspect that all the overhead of both
> XFS and LVM where causing enough latency to be a problem. In case you
> were wondering, the third partition is now dedicated to my dvd rips and
I had a similar issue not too long ago. I was tweaking the hell out
of my frontend, blaming it for the playback problems and only realized
it was the backend after some streaming issues with another app.
I'm still not sure exactly why the backend was performing poorly.. it
had plenty of CPU, decent disks, and everything looked fine on it.
But, after re-installing that system it worked fine. The old
install was running Ubuntu (6.04, I think) and using LVM. My new
install is Ubuntu Feisty, non-LVM, with jfs filesystems for myth
Is this common with LVM? Or maybe an older version of LVM like I was using?
Any recommendations for others to diagnose this? It wasn't clear at
all where the problem was.. If I remember correctly, and I may not
be, the hdparm performance numbers for the LVM filesystem were fine.
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