[X2Go-User] Jerky Video Fixed

Thu Apr 2 18:17:34 CEST 2015

Robert

Thanks for all of your information on the low latency kernel.   I've used
x2go for several years and one use-case I've had was to install the x2go
server onto either Amazon's AWS EC2 or on Digital Ocean to support remote
desktops for K-12 schools that I do volunteer work for.

Clients have always been a mix of Win7, Mac or Ubuntu linux.

Really the only issue has been video streaming which for K-12 is important
because alot of learning content online consists of video.

In the past I've tried using larger "compute" instances (8-16 core) in
those clouds thinking perhaps the video encoding/transmission load was the
cause but that only improved things marginally.

I tried higher bandwidth links... same marginal improvement.

It didn't matter what client they used (mac, win7 or linux) the video
content viewing results was more or less the same for each.
That's why I am thinking maybe only the server-side "may" be required to
have the low latency kernel??

I got them all so the streaming video (say youtube) wasn't awful but it
wasn't the same as watching the video on a dedicated PC instead of thru the
x2go virtual desktop.

But i guess I never suspected the linux kernel introducing delay/jitter to
the point of being the cause.

It may take a while until I can get to it but I'll try and set up a test
with one of those clouds and have the x2go server-side ubuntu utilize the
low latency kernel you described and see what happens with each client.

This would be great if that turns out to be the source of streaming video
jerkiness for cloud based remote desktops.   I'll post something to the
x2go alias when I find out what happens.

thanks again.

Brian

On Wed, Apr 1, 2015 at 5:55 PM, Robert Dinse <nanook at eskimo.com> wrote:

>
>      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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>>> Hosting.
>>>    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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>>
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