[mythtv-users] judder problems with nvidia 358.16

Mon Mar 14 14:34:39 UTC 2016

Hi all,

 Short, deliberate top posting to say that the problem remains after following bottom-posted workflow.

On Tuesday, 8 March 2016, Marius Schrecker <marius.schrecker at lyse.net> wrote:Stupid of me not to check that! The GUI refresh rates are the NVIDIA "false" rates: 50Hz, 51 Hz, 52 Hz, etc..  That's what your problem is then, 50Hz is the closest to 23.93. So myth is doing the right thing as far as its concerned.  Which version of Xrandr do you have installed?libxrandr2 : 1.5Myth only supports 1.2 or the nvidia X extension(libnvctrl) , but this needs to be installed and present. Normally the nvidia installer would install it automatically. 
 Hmmmm. This is proving to be black magic.  Explicitly adding the module load directive to xorg conf does result in:

343408.826] (II) LoadModule: "nv-control"
[343408.826] (WW) Warning, couldn't open module nv-control
[343408.826] (II) UnloadModule: "nv-control"
[343408.826] (II) Unloading nv-control
[343408.826] (EE) Failed to load module "nv-control" (module does not exist, 0)

So I started digging.

 There IS a Ubuntu package called:

 libxnvctrl0

so I installed it.
# apt-cache show libxnvctrl0
Package: libxnvctrl0
Priority: optional
Section: libs
Installed-Size: 74
Maintainer: Ubuntu MOTU Developers <ubuntu-motu at lists.ubuntu.com>
Original-Maintainer: Debian NVIDIA Maintainers <pkg-nvidia-devel at lists.alioth.debian.org>
Architecture: amd64
Source: nvidia-settings
Version: 352.21-0ubuntu1
Depends: libc6 (>= 2.14), libx11-6 (>= 2:1.4.99.1), libxext6
Filename: pool/main/n/nvidia-settings/libxnvctrl0_352.21-0ubuntu1_amd64.deb
Size: 11534
MD5sum: 69b4410f3c2428d3e2bfbc851ae3f4b2
SHA1: 1a0ef460048106be1fed88d668d53680767a1a69
SHA256: 9f81e8f9e8c10551e047dad6de23800fd9d69365f32bb2419da16851b4f7c6c8
Description-en: NV-CONTROL X extension (runtime library)
 The NV-CONTROL X extension provides a mechanism for X clients to
 query and set configuration parameters of the NVIDIA X driver.
 State set by the NV-CONTROL X extension is assumed to be persistent
 only for the current server generation.
 .
 This package contains the shared library.
Description-md5: 6d4f8aebac836277193a58e922a49603
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu
Supported: 9m

 The version is  352.21-0ubuntu1

 and itseems to install the library file libXNVCtrl.so  to /usr/lib:

# locate libXNVCtrl.so
/usr/lib/libXNVCtrl.so.0
/usr/lib/libXNVCtrl.so.0.0.0

 (NOT to "/usr/lib/xorg/modules") which is where Xorg is expecting to find them.

 Question 1: Should I symlink?

I then looked in the nvidia driver source for traces of the same library, but found nothing, so either it has a different name here or needs to be downloaded separately, but I have yet to find where.

As the packaged version of the livrary was 352.21, I decided to try again to install the same version of the driver, first using the sgfxi script (which refuses), then using the pre-packaged version, which looses my nvidia GLX extension.

So that's where I am so far.

 Maybe the control library doesn't need to be in the same version as the rest of the driver, in which case I could reinstall 358 or 361 from source (sgfxi or manual build) and run against  libXNVCtrl 352.21 symlinked to /usr/lib/xorg/modules 

 Otherwise I do need to work out where to find or how to build the version of the library matching a buildable driver.

any clues?

 BR.

--Marius--

  If you completely clear any nvidia drivers and install from nvidia official installer. Does it work? When starting X do you see any error about not being able to load the nvctrl X extension? Do you see anything in mythtv log about being enable to access it? That would explain why you are seeing this.  An alternative is to disable nvidia TwinView; then the refresh rates reported to Xrandr will be the real ones (though as Xrandr 1.4 and earlier can only deal with integers, you will only get things like 24, 25, 30 50, 60, not 59.997)  Then it will automatically set your screen to the right refresh rate, provided your screen supports it. (To test if changing refresh rate works, when you play with xrandr do you see the refresh rate the screen is getting changing?) Xrandr reports and sets the real refresh rates (confirmed with TV)

In the meantime I also added the mythuser (login user) to audio and set up limits.conf as per the wiki. Don't need that IMHO. Those instructions were written like 10 years ago, all obsolete with the new audio stack which was added like in 2009 or something! 
BR.

Marius