[mythtv-users] 1080p choppy playback

Andrew Gallatin gallatin at cs.duke.edu
Fri Jan 11 21:09:34 UTC 2008

Mat Kyne [matkyne at hotmail.com] wrote:
> I recently purchased a 1080p LCD. I am feeding it a 1080p signal from
> my MythTV box over the VGA cable. Everything looks great, but when I
> playback 1080i content recorded over the air HD, playback is choppy. I
> have a Nvidia FX5200 graphics card and am using the Nvidia binary
> drivers. The rig has a Pentium 4 3 GHz CPU and 512 MB of RAM. I had no
> problems with playback before I switched to this TV. My previous
> display was a Sony CRT HDTV, and was fed from a VGA to Component
> Transcoder. I have not checked yet but I don't think that I am taxing
> the processor and I am well below the maximum resolution and refresh
> rate of the video card. I am using BOB to deinterlace playback. I am

I've got the exact same hardware as you (old 3.0GHz P4, NV5200 feeding
1080P LCD via VGA), and I also upgraded from a CRT HDTV using a VGA to
Component transcoder.  FWIW, I'm running Ubuntu 6.10, kernel
2.6.17-10-generic #2 SMP, and the Nvidia binary package (8776).
I'm also using Bob interlacing, together with XvMC.

My system is teetering on the edge of being able to handle 1080i.  I
have to disable any queue processing (eg, commercial flagging) during
hours when I'm likely to be watching TV.  Even then, if I'm recording
more than one show while watching a 1080i show, things skip a lot.  I
can mitigate this somewhat by disabling interlacing on the fly (go
into the playback menu, select a progressive video scan).

> looking for suggestions, maybe I am using the wrong filter, or would I
> have better results if I used a DVI/HDMI cable instead of VGA? Maybe
> someone has run into the same problem before.Thanks in advance.

I don't think this would help, and may also open a whole new can of
worms.  When I tried DVI with the version of drivers I'm running, the
X server crashed.  I think there is a workaround, but I don't have a
lot of time to mess with it at the moment.

BTW, I was previously running my 1080i CRT at 720P due to the Nvidia
interlace bugs.  I didn't notice HD playback getting *that* much less
reliable when I upgraded to a 1080P LCD, which surpised me.  I
expected to have to run it at 720P until I upgraded the FE.  Did your
old setup work much better than what you have now?


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