[mythtv-users] playback not smooth regardless of source

Seth Daniel mythtv.org at sethdaniel.org
Mon Feb 26 08:04:22 UTC 2007


I have a combined FE/BE myth box.  AMD64 3800+, AM2 motherboard, 1G
memory, Nvidia 6200TC.

I have searched this mailing list up and down looking for a workable
solution to my playback problems.  No matter what I playback I get
jitters or stutters (not sure what the difference is).  It is especially
pronounced during horizontal panning.  I have no audio problems.  Plenty
of people have reported this in past e-mails.  Responders have suggested:

  - disabling vertical sync; enabling vertical sync; enabling flipping 
    etc... in nvidia-settings.

    I have done this and tried any number of combinations.  If I turn
    all syncing off I get tearing (which seems pretty typical).  Hard to
    tell if the jitters go away with all the tearing going on.  I've 
    also enabled and disabled the GL sync option in the frontend
    settings with no effect.

  - using various deinterlacing methods (bob; linear; etc...) or turning
    deinterlacing off.  

    Tried these.  Same problems.  I typically run with Bob deint.

  - pci latency tuning

    My motherboard doesn't appear to support this (setpci has no effect).  
    The BIOS doesn't have any options for setting latency.

  - turn off compositing in xorg.conf

    Did this to no effect.

  - turn on realtime thread scheduling (this I found in the mythtv howto)

    Followed the instructions.  No difference in playback.

  - turn DMA on for hard drive
    I have an SATA drive.  AFAIK the DMA is always on and you can't tune
    or see the setting through hdparm.

I have tried different resolutions.  Specifically 1080i and 720p.  Both
have the same jitteriness.  I normally run at 1080i.  This happens with
pre-recorded SD TV shows, ripped DVDs, live TV, and live DVDs.   

The processor is dual core and playback rarely pushes any single core
over 20%.  Except for the frontend nothing else is doing much of

I am running a lightweight window manager (openbox).  Ubuntu Feisty with
the latest Ubuntu Feisty myth packages (one person claimed they had the
same problems I am having and resolved the problem by rolling their own
packages.  That would be my solution of last resort).   

By default the frontend logs rarely log anything.  When I ran the
frontend with the 'all' log option I didn't see anything interesting.
Then again I may not know what interesting would be. 

seth / @sethdaniel.org
I used to jog, but the ice kept bouncing out of my glass.

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