[mythtv-users] 0.24+fixes - tearing, /dev/rtc permissions and getting openGL to work

Mark Kendall mark.kendall at gmail.com
Thu Feb 24 01:58:25 UTC 2011


On 24 February 2011 09:33, Mike <mythtv at dtmc.ca> wrote:
> In the pursuit of a perfect mythtv frontend, I have recently bought a
> Zotac Nvidia ION frontend which I have compiled and installed mythtv
> 0.24+fixes on U10.10.
>
> HD playback works with three things that are bugging me and I can't
> find a solution despite scanning fourms & blogs.
>
> i) very slight tearing about midway across the screen typically on
> horizonatl panning
> ii) /dev/rtc is symlinked to /dev/rtc0 which only have root access permissions
> iii) Player(0): Waited 100ms for video buffers messages occasionally
> iv)  I have seen, with usleep moreso, the sound lagging the video
>
> The tearing problem is likely related to Vsync and OpenGL.  I have
> instructed nvidia-settings to enable this feature.  However, in (ii) I
> see it using usleep unless I start mythfrontend as sudo/root.  Then I
> see RTC.  I've never seen OpenGL method.

Enabling OpenGL vsync in nvidia-settings will do nothing for VDPAU
tearing. NVIDIA's VDPAU implementation is entirely standalone in that
respect and manages vsync separately.

There is no OpenGL vsync in MythTV as of 0.24.

> What I would like to know is how to ensure/check/enable OpenGL as this
> seems to be a problem with tearing and possibly the timing method.
> Problem (iv) seems to be much better when RTC is used so how do I fix
> (ii)?  I can change the permissions but they dont persist a reboot.
>
> I see OpenGL is available as I have advanced desktop effects working.

This is the root cause of your problems. You need to disable the
composite extension (search the wiki and/or the list archives). Using
the composite extension will not only hurt performance (you want those
GPU cycles for deinterlacing etc - especially on an ION board) but
will also break vsync. From memory, there may be a compiz setting that
works around the vsync issue but you're really better off without it.

regards

Mark


More information about the mythtv-users mailing list