[mythtv-users] Live HD TV jumpy

William Munson william_munson at bellsouth.net
Wed Jul 11 11:55:33 UTC 2007

DaveD wrote:
> My setup, for the most part is working quite well.  I have a pcHD3000, a
> DVICO Gold, and a PVR-500.  This gives me two HD and two analog (I
> haven't used the analog portions of either HD card for "sound" reasons,
> NPI).   The recording and playback is working quite well.  I can watch a
> full 1020i or 720p HD recording while all 4 tuners are recording!  I
> find this amazing, but with the tuners doing all the work, recording is
> just dumping onto the disk.  HD playback is another story; CPU usage
> runs pretty high (about 90%, mostly Xorg, then Mythfrontend), no matter
> what the tuners are doing.  Still, it all works well.  Until I try to
> watch live HD TV.  Live standard def works fine, but HD is jumpy and
> blocky.  Badly so.  So bad that Myth gives up, some times, and says "an
> error was encountered while displaying video" then dumps me back to the
> menu.  I don't really understand this.  Isn't live TV just like watching
> a recording while another show is being recorded?  It just happens to be
> the same show.

Watching "live tv" is the most cpu and disk intensive activity you can 
do with myth. Not only are you saving the file to disk you are playing 
it back too. This doubles the thru-put on the drive and also applies a 
pretty big mysql database activity load. Throw in a comm flag and 
another recording or two and you have maxed out the hard drives or the 
IDE/SATA channel. Also, your cpu usage while playing the stream says you 
are maxed out in that regard too. Adding a line to your xorg.conf file 
may help lower your usage. In the  (I think) device section add an option

Option "UseEvents" "True"

This should lower your Xorg usage by 40-50%

Also the deinterlace setting you choose and the decoding method chosen 
will have a large effect on  frontend cpu usage. I find that the linear 
blend deinterlace setting is the most efficient and for me libmpeg is 
the best decoder choice. Although xvmc gives a lower cpu usage, the lack 
of color in the pop-up windows makes it a undesirable choice for me.

Bad HD video playback is a common complaint so do a bit of searching for 
other ideas to check. With your processor you should be able to watch HD 
with less than 70% processor usage once everything gets fine tuned a bit.

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