[mythtv-users] Stuttering

[Nedim Cholich]

On 6/15/06, William Powers <wepprop at sbcglobal.net> wrote:
>
> Thomas Worthington wrote:
> > I'm recording from DVB-T so the files are normal mpegs. They play
> > perfectly in mplayer without realtime threads, but even with realtime
> > enabled the same files have a tiny stutter about every three seconds.
> This
> > is no problem most of the time but during tracking shots or text
> scrolling
> > it is very distracting.
> I just recently finished a long period of trial and effort to eliminate
> the same kinds of stuttering you describe.  In my case, I only saw the
> stuttering while the transcoder was running, but that still happened
> often enough to be annoying.  I tried a lot of things, cheapest first,
> and a few of them helped but most of them didn't.  In my case, the
> things that did help are, ranked from most help to least help:
>
> 1.  Increased physical memory, first from 512M to 1G, then to 2G.
> 2.  Upgraded from a 2.8G Northwood P4 to a dual-core Pentium D 820.
> 3.  Changed the hard drive used to hold the video partition from PATA100
> to SATA150.
> 4.  Enabled write-caching on the hard drive used to store the recordings.
> 5.  Set 'swappiness' to zero.
> 6.  Reduced the PCI latency of the VGA card to be in-line with that of
> other devices.
>
> Because I didn't perform them in that order, I can't be certain I would
> have had to do all of them to fix the problem.  For example, increasing
> the physical memory from 512M to 1G is what finally ended the stuttering
> completely.  It's possible I would never had to do some or all of the
> others if I had increased the memory first.


I used to have stuttering but only when playing HD content. I refused to
think that it was hardware problem since my hardware had plenty of power for
even 1080i shows. I googled and tried every conceivable option. After much
trial and error I realized (based on no scientific evidence) that using xvmc
(out of all things) was causing the stuttering. This was both with an
on-board nvidia 6150 and PCIe 7300GS. I turned off xvmc, played with vsync a
bit and the stuttering went away.

Another interesting thing I found which I only have speculations about is
that 1080i content is playing smoother then 720p even though 1080i is
suppose to have more "data". I guess the fact that it's interlaced and has
only 540 lines in each frame is making it play smoother but I may be talking
complete nonsense. After all 1920x540 is still larger then 1280x720. Hmm...
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-users/attachments/20060615/55e65914/attachment.htm