Re: [X2Go-User] Jerky Video Fixed

  In Ubuntu, they build low latency kernels and make them available as

part of the distribution but not installed by default.

  On my workstation, which is an old Mac-Pro 1,1 with quad Xeon CPU's and

4 GB of RAM, I had Ubunto 14.04 installed then upgraded to 14.10. I had Wine installed and under Wine I ran WinAmp to play music. WinAmp sometimes skipped, and also when I upgraded to 14.10 which came with a 3.16.x kernel, I had issues with the Nvidia drivers for my old 7300 GT card.

  To solve those issues I ended up building a 3.18.9 kernel and built it

with kernel preemption enabled, which is how Ubuntu builds their low latency kernels. That solved both my issues with Nvidia drivers and with WinAmp stuttering but it did not fix the issues of video being jerky over X2Go, and I had pretty much written that off to my Comcast connection anyway.

  But given how much smoother things went on my workstation, I decided to

try installing the low latency kernel on the server and then tried watching some Youtube videos that had previously been jerky (audio okay but video jerky) and found that it made the video smooth.

  So my guess is you probably need it on both, but since I haven't tried

it on the server only I can't say for sure.

  The kernel on the server isn't custom built, it's one of the low latency

kernels provided by Ubuntu (I used synaptic package manager to select and install, rebooted, then removed the old).

  On the Mac I don't know.  I had so much problems with X2Go on my Mac, even 

after installing the XQuartz server, that is one of the reasons I installed Ubuntu on it and stopped using MacOS. Got tired of the spinning beach ball, got tired of having zero games available. I liked the Dock but that's about it. Mac's approach of just throw enough hardware at it and it will be acceptable works if you have infinite money, I don't.

  With respect to Windows, I only have an old antique XP machine that I use

for some games, don't really know how it would work with video over X2Go so can't answer that one.

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On Wed, 1 Apr 2015, brian mullan wrote:

Date: Wed, 1 Apr 2015 17:36:06 -0400 From: brian mullan <bmullan.mail@gmail.com> To: Robert Dinse <nanook@eskimo.com> Cc: x2go-user@lists.x2go.org Subject: Re: [X2Go-User] Jerky Video Fixed

Robert this is very interesting.. mainly because I wasn't aware there was such a thing as a low latency kernel. Guess with linux you are always learning. However, I have an experimental question. Is it just the kernel on the video transmitting side, the client/receiver side or both that the low latency kernel has this impact? Also, if the video server side is linux with a low latency kernel then what would a client running x2go on a mac or a windows 7 machine experience since neither utilize a linux kernel ? Thanks for sharing as I had always figured it was a latency problem but I assumed it was 100% due to the network itself. Bria On Apr 1, 2015 5:23 PM, "Robert Dinse" <nanook@eskimo.com> wrote:

...

 I hope I've done this in a way that doesn't steal anyone else's

thread.

 A while back someone posted that they had somewhat jerky video through

x2go, and I posted that if I watched someone on youtube over an x2go connection, with a 20 mbit/s cable connection, on a Ubuntu 14.10 client accessing a Ubuntu 14.04.2 LTS server, I also had some jerkiness to the video.

 I have installed low latency kernels on both machines now and that

eliminated the jerkiness. I can now watch a youtube video on a remote machine and have it display smoothly even with the highest quality setting set.

 Just posting this so if others are experiencing this problem this may

be a viable fix for them.

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