[mythtv-users] More HD stuttering

Todd Ignasiak ignasiak at gmail.com
Fri Dec 2 13:47:46 EST 2005

I display all my programs on a 1280x720p LCD panel, with my output
resolution set to 1280x720 @ 60fps.    Both 1080i and 720p work just
In fact, 1080i is working better than 720p for me, because I get some
stuttering when the OSD is up with 720p when using XvMC.  Without
XvMC, playback is completely reliable with both 1080i and 720p, it
just takes more CPU power.

Scaling the video to the display resolution seems to be a pretty easy
job for the system.   I'm not sure what portion of that is done in
software/cpu versus what is done on the video card.  But, It is
certainly much less intense than scaling and recompressing the
MPEG2/MPEG4 video.

My System: Athlon64 3200+ 768MB RAM, NVidia FX5200, Nvidia drivers
7676, Gentoo X86-64, Linux kernel 2.6.14.   MythTV - latest SVN.

On 12/2/05, Chris Trown <ctrown at safe-mail.net> wrote:
> Jean Connelly wrote:
> >
> > Regarding:
> >
> >           The system is a 3.06 GHz P4 running Fedora Core 3.  The video Card
> >     is a NVidia 5200FX.  For capture, all I have is a HD3000.  I've checked
> >     that DMA is working on all the drives.  I built mythtv from stable
> >     source, 0.18.1.  I used the following configure options:
> >
> >     --enable-xvmc --enable-opengl-vsync --enable-dvb
> >     --dvb-path=/lib/modules/2.6.12- 1.1381_FC3smp/build/include
> >     --disable-firewire --disable-joystick --disable-ivtv --enable-proc-opt
> >     --disable-xvmc-vld --enable-opengl-vsync
> >
> >
> > I have close to an identical system; and I have what is probably
> > equivalent stuttering.  HDTV (live or recorded) is totally unplayable in
> > myth.  I have tried with and without opengl sync.  I can't find the xvmc
> > option in the gui with this myth version to disable xvmc for testing.
> > Recorded 1080i plays badly (with frequent pauses and never with audio
> > sync) in mplayer with xvmc and ffmpeg12mc and plays even worse without
> > xvmc.  I'll try transcoding my latest sample clips to see if they are
> > fine when played back at standard resolutions.
> >
> > I've got
> > 3.06 GHz P4 (which is a 533Mhz FSB chip)
> > 512 MB Ram
> > BE7-RAID mobo
> > Nvidia 5200FX
> > Fedora Core 3
> >
> > Night before last's myth svn.  No deinterlacing requested.
> > Prebuffer pauses all over the place.
> >
> > I think what we really need is an hdtv playback test suite external to
> > myth to get better benchmarks on actual system performance.  From
> > previous posts to the list ("well I got *my* P4 1.4Ghz system to
> > playback hdtv") I think that my system *should* be able to playback hdtv
> > without issue, but perhaps there are some motherboard weaknesses or such
> > that make it impossible.
> >
>       After some tinkering, I found out what the problem was.  I think.
>   I was trying to play a 1080i stream on a 720p screen.  What I think
> was happening was that the 1080i stream could not be rendered using XVMC
> to 720p.  It had to me done in software, ie: the CPU.  When I changed
> the display to 1920x1080, XVMC kicked in and the image played nicely, so
> long as it was done by root.  No, I wasn't using xrandr.  I will when I
> get everything going under Core 4.
>       This prompted my to "upgrade" to Core 4 so I can get realtime
> priority threads via PAM.  I don't really consider it an upgrade.  My
> experience is that Core 4 has more issues than Core 3.  Case in point,
> try compiling 18.1 stable with GCC4.  But I like the idea of running
> mythfrontend as root more distasteful than the problems.
> Chris...
> --
> "Those who would give up essential liberty to purchase a little
> temporary safety deserve neither liberty nor safety" -- Benjamin
> Franklin
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