[X2Go-User] Jerky Video Fixed

[Robert Dinse]

      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 at gmail.com>
> To: Robert Dinse <nanook at eskimo.com>
> Cc: x2go-user at 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 at 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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>>    Knowledgeable human assistance, not telephone trees or script readers.
>>  See our web site: http://www.eskimo.com/ (206) 812-0051 or (800) 246-6874
>> .
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>