[mythtv-users] Problems with HDTV -- Frontend or backend?

Ryan Steffes rbsteffes at gmail.com
Sun Sep 16 23:55:08 UTC 2007

On 9/16/07, William Munson <william_munson at bellsouth.net> wrote:
> Ryan Steffes wrote:
> > I just got my A180 up and running, and am experimenting with it.  I'm
> > recording OTA channels now, because setting up the QAM channels proved
> > to be beyond me.  I THINK I'm getting good recordings, but I can't be
> > positive because I can't seem to get them to play back properly.  I'm
> > trying to figure out if the problem is on the recording or playing
> > end.
> >
> > I'm playing through an NVIDIA GeForce4 Ti 4200 to a standard
> > resolution TV.  I'm guessing that, despite not being an HDTV, all the
> > normal trouble with heavy bandwidth still apply, correct?  When I tune
> > to the recordings off the A180, the run super slow motion with no
> > sound at all.  If I watch the slow motion long enough, I get a burst
> > of normal sound or a snap/pop.  I also get funny boxy glitches on the
> > screen every once in a while.
> >
> > I'm currently transcoding a HD programing to see if I can watch it
> > afterwards, but I thought I'd sent out a request for information
> > before I crash for the night.  Basically, I'm trying to figure out if
> > these problems seem to indicate a problem with the recordings
> > themselves, or a problem with the playback.  Also, I'd kinda like some
> > confirmation that those lines about XvMC mean I do have it configured
> > right (the screen isn't black and white like searches in the mailing
> > list have suggested might happen).
> >
> > Thanks for any help,
> >
> >
> Video capture of hd material especially only one channel capture is not
> likely to strain your system storage subsystem. Most likely you are
> running out of processor displaying the video. Run top in another window
> and see what your cpu usage while recording and playing back your video.
> I suspect you are maxed out during playback.
> On my system (FC6) I had to manually change the xvmc libs link to point
> to the correct xvmc file to enable xvmc. You should be able to find this
> info in the myth docs on the wiki. When working correctly you should see
> a 30-40% reduction in xorg usage during HD playback.
> Also, most people  have to add an option to their xorg.conf to enable
> the "UseEvents" functionality which will also make a big difference to
> your cpu usage. Again, look in the wiki.
> Bill

I did what it said in the Wiki, but what I did NOT do was try enough
other channels.  I'm thinking I may need a better directional antenna,
because I discovered when I tuned to a channel being broadcast from a
different location (most of the channels around here are off the same
tower), it came through very nice, but with lots of prebuffering
pauses.  Following the tips and tricks in the wiki seems to have
sorted most of that out. I've got an AMD 2500+ with a GeForce Ti4200,
and on a crystal clear HD channel, it seems to play it alright.  When
there's any kind of signal degradation (which is just about every
channel for me), it can't seem to handle it at all, however.  I'm not
sure why that is, but when the reception gets bad, it can actually
crash mythtranscode or mythfrontend.



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