[mythtv-users] XvMC and CVS

dean vanden heuvel deanv at cox.net
Wed Sep 8 23:41:46 EDT 2004

Thanks for the reply...

It is the video output itself that is the problem.  When I enable XvMC and disable interlace (from the frontend), and use a 1920x1080i output (which you are correct, my TV can handle), the video looks very *blocked*, sort of like each pixel is VERY large.  Diagonal lines are truly stepped, etc.

In the past, I was using XvMC (no deinterlace, as none was possible in 0.15) driving the 1080i, resulting in a reasonable picture.  However, it seemed like scaling from the recorded 480i up to 1080i, only to have my TV scale back down to 720p (its native display mode) could be causing some degradation.  I figured that using Myth to scale from 480i to 720p, thus doing NO SCALING in my TV might improve things.  It may have (I cannot really tell because it takes too long to change from one to the other), but the bob deinterlace (without XvMC) makes the picture jumpy and movement in the XvMC mode seems to be slightly jerky, so I thought a return to 1080i might be in order...thus my question.

It is the poor-man's deinterlace that really messes things up.  Bob just sometimes (although not with XvMC) messes with horizontal lines.  Seems like what I need it XvMC without deinterlace.  I will try your suggestion.

thanks again.


On Wed, 8 Sep 2004 19:43:41 -0400 (EDT)
Daniel Thor Kristjansson <danielk at mrl.nyu.edu> wrote:

> On Wed, 8 Sep 2004, dean vanden heuvel wrote:
> ]question...is there a way to turn off ALL deinterlace in the current
> ]CVS version of the code?
> ]-dvh
> Is it the OSD that is the problem, or the video output itself?
> There are two major changes in the output at 1080i, one is a poor-man's
> deinterlacing, and the other is bob-deinterlacing. The first would lower
> quality on a display with a true 1920x1080 interlaced scan, and the
> latter would improve quality a on a display capable of 60hz 1920x1080
> progressive scan (your DLP can probably do that). But both have bad
> looking OSD because we haven't gotten around to fixing that.
> A hackish way to disable all deinterlacing is first uncheck
> deinterlacing in setup, and then change detectInterlace()
> in NuppelVideoPlayer.cpp to always return kScan_Progressive.
> If you're using CVS as of today you should notice smoother output with
> 1080i content, if you first run "chmod a+s /usr/local/bin/mythfrontend"
> as root. This will allow mythtv to run the display thread with
> a real-time priority.
> -- Daniel

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