Am 2016-01-17 17:47, schrieb SternData:

On 01/17/2016 10:42 AM, Joey wrote:

...

Dual-Screen Solution without connected a second Monitor

What is a dual screen solution without a second monitor? Are you talking about virtual desktops?

Yes. if this virtual Desktop is useable like a normal Desktop (for example change position in kde systemsettings)

Am 2016-01-17 18:09, schrieb SternData:

On 01/17/2016 10:58 AM, Joey wrote:

...

Am 2016-01-17 17:47, schrieb SternData:

...

On 01/17/2016 10:42 AM, Joey wrote:

...

Dual-Screen Solution without connected a second Monitor

What is a dual screen solution without a second monitor? Are you talking about virtual desktops?

Yes. if this virtual Desktop is useable like a normal Desktop (for example change position in kde systemsettings)

I don't use KDE, but I see lots of info googling on "enable KDE Virtual Desktop"

But this means other things. i think i need a virtual device for dual screen using.

Am 2016-01-19 02:01, schrieb Mark LaPierre:

On 01/17/16 11:42, Joey wrote:

...

Hello List,

i want to use a Dual-Screen Solution without connected a second Monitor.

Its a solution available, that a physical monitor/Device is simulated? I want to use it on KDE.

Thank you.

Joey

Hey Joey,

Does your current physical monitor support multiple connections? Most modern monitors do. If it does then you can connect a second video cable from your computer to your monitor. There you have it. A duel monitor connection.

Hey,

thx for this tricky idea! Unfortunately i need it for notebooks ..

When i do presentation i have this workflow:

I connect the beamer on my notebook so i have dualscreen. On my notebook screen i have all icons/windows i need. The things i want to show i move to the 2. desktopscreen (the beamer).

If i want to be independent of the cable-end of the beamer i do this:

i connect a second monitor to my notebook and i stream the screen of the 2. monitor with ffmpeg / ffserver (installed on my notebook). a other device eg notebook, which is connect to beamer, show my stream on the beamer.

Very nice solution for me :). I want to extend the solution that i dont need a monitor connected to my notebook. I dont know how can i get a second desktop is useable like a dualscreen.

Greetings Joey

Am 2016-01-19 16:57, schrieb Mark Haney:

I'm curious as to what exactly you are needing what appears to be a second monitor without an actual second monitor? For what purpose do you think you need such a setup? Maybe there's another method to get what you want if you can give us more detail.

On Tue, Jan 19, 2016 at 10:53 AM, Joey forum@r5d.de wrote:

...

Am 2016-01-19 02:01, schrieb Mark LaPierre:

...

On 01/17/16 11:42, Joey wrote:

...

Hello List,

i want to use a Dual-Screen Solution without connected a second Monitor.

Its a solution available, that a physical monitor/Device is simulated? I want to use it on KDE.

Thank you.

Joey

Hey Joey,

Does your current physical monitor support multiple connections? Most modern monitors do. If it does then you can connect a second video cable from your computer to your monitor. There you have it. A duel monitor connection.

Hey,

thx for this tricky idea! Unfortunately i need it for notebooks ..

---

CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

--

Mark Haney ::: Senior Systems Engineer *VIF* International Education P.O. Box 3566 ::: Chapel Hill, N.C. 27515 ::: USA 919-265-5006 office

Global learning for all. www.vifprogram.com http://www.vifprogram.com/?utm_source=signature&utm_medium=email&utm_campaign=VIF Find VIF on Facebook http://facebook.com/VIFInternationalEducation | Twitter https://twitter.com/vifglobaled | LinkedIn http://www.linkedin.com/company/vif-international-education

Recognized as a ‘Best for the World’ http://bestfortheworld.bcorporation.net/ B Corp! _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

Am 2016-01-19 20:28, schrieb Jonathan Billings:

On Tue, Jan 19, 2016 at 05:11:22PM +0100, Joey wrote:

...

i connect a second monitor to my notebook and i stream the screen of the 2. monitor with ffmpeg / ffserver (installed on my notebook). a other device eg notebook, which is connect to beamer, show my stream on the beamer.

Very nice solution for me :). I want to extend the solution that i dont need a monitor connected to my notebook. I dont know how can i get a second desktop is useable like a dualscreen.

Could you use Xephyr (xorg-x11-server-Xephyr package in centos7) as a nested X environment for the streaming screen?

i try xephyr/xnest, but i dont recognize how i can use a nested display like a second screen.

Yes, with a cable connect it is possible, of course.

But i dont like it to be restricted in my movement by wired to a hdmi-cable. :-)

Am 20.01.2016 um 15:07 schrieb Jonathan Billings:

On Tue, Jan 19, 2016 at 10:49:31PM +0100, Joey wrote:

...

i try xephyr/xnest, but i dont recognize how i can use a nested display like a second screen.

I guess I still don't understand why you need a second, virtual screen.

Every projector I've ever used appears as a second screen on my linux desktop, and I have the choice to either mirror my display or expand my desktop across both. If you choose the second option, you can put your projector content on the projector, and keep your laptop's display for notes.

Does your projector not do that? I don't understand the situation where you need to use a second computer and ffmpeg streaming.

Yes. Sometimes i go to the front like a teacher and then i go to the groupdesks. And i hate it always to go back to the front where the cable of the beamer ends only to use my device and to show the whole participants things on the beamer. This feels so much last millenium.

Am 20.01.2016 um 18:50 schrieb m.roth@5-cent.us:

Joey wrote:

...

Am 20.01.2016 um 15:07 schrieb Jonathan Billings:

...

On Tue, Jan 19, 2016 at 10:49:31PM +0100, Joey wrote:

...

i try xephyr/xnest, but i dont recognize how i can use a nested display like a second screen.

I guess I still don't understand why you need a second, virtual screen.

Every projector I've ever used appears as a second screen on my linux desktop, and I have the choice to either mirror my display or expand my desktop across both. If you choose the second option, you can put your projector content on the projector, and keep your laptop's display for notes.

Does your projector not do that? I don't understand the situation where you need to use a second computer and ffmpeg streaming.

Yes, with a cable connect it is possible, of course.

But i dont like it to be restricted in my movement by wired to a hdmi-cable. :-)

You walk around with a laptop during a presentation?

   mark

---

CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

Virtual Display have different meanings.

i need a solution like a dualscreen. i want to move with mouse windows from one screen to the other. and i need that i can stream the 2. screen for example with ffmpeg. with ffmpeg i can stream a part of the desktop (also the second screen)

i try to use the panning function of x-server. but with panning (desktop larger then monitor) the controlpanels and widget of the screen are resized and spread to the whole desktop. after resize a lot of preferences are destroyed :-(

maybe its possible to use a nested xserver, but i dont know how i could make xephyr or xnest available for kde as second device.

Am 20.01.2016 um 19:26 schrieb Jonathan Billings:

On Wed, Jan 20, 2016 at 04:54:40PM +0100, Joey wrote:

...

Yes, with a cable connect it is possible, of course.

But i dont like it to be restricted in my movement by wired to a hdmi-cable. :-)

So how would a second, virtual display help?

Thank you Jonathan for your participation.

But i only want the same workflow like a second device is wired.

A hoped its possible to configure a second xorg-server or a fakedevice/-monitor that kde recognize this and you could use this as second desktop in same way as in dualscreen-modus.

So i ask a lot of people the last days and ok, maybe tis solution seems unavailable without deeper knowhow.

Thank you all. J

Am 20.01.2016 um 21:50 schrieb Jonathan Billings:

On Wed, Jan 20, 2016 at 08:49:02PM +0100, Joey wrote:

...

Virtual Display have different meanings.

i need a solution like a dualscreen. i want to move with mouse windows from one screen to the other. and i need that i can stream the 2. screen for example with ffmpeg. with ffmpeg i can stream a part of the desktop (also the second screen)

i try to use the panning function of x-server. but with panning (desktop larger then monitor) the controlpanels and widget of the screen are resized and spread to the whole desktop. after resize a lot of preferences are destroyed :-(

It sounds like what you want to do is use Xdmx (xorg-x11-server-Xdmx package) with maybe x11vnc on the system hooked up to the projector.

On Jan 20, 2016, at 5:08 PM, Jonathan Billings billings@negate.org wrote:

On Jan 20, 2016, at 5:00 PM, Joey forum@r5d.de wrote:

...

A hoped its possible to configure a second xorg-server or a fakedevice/-monitor that kde recognize this and you could use this as second desktop in same way as in dualscreen-modus.

This is why I suggested Xdmx.

The X protocol is a far better choice for this sort of application than video codecs, especially over a wireless LAN. The local X server inherently knows when changes occur that it needs to send to the remote X server, whereas with video, each frame of video has to be treated like a new world, with a brute-force search over the frame for parts which have remained unchanged, so they can be optimized out.

And even then, a video codec is going to wastefully send frames even when it doesn’t have to, because it’s designed with the assumption that *something* changes in every frame, even if it’s just a text crawl and the talking head’s lips on CNN.

That said, X is fairly laggy, increasingly so as GUIs have become piggier. (More pixels, more colors per pixel, more use of gradients and such rather than solid fills, antialiasing, etc.)

Then on top of that, by using wifi, you’re going back in time something like 10 years in terms of bandwidth and latency compared to the wired LANs where X grew up. I just did a test here from my desktop: 36 Mbit/sec and 32 ms average ping time over wifi to a server that gives me 940 Mbit/sec and 0.35 ms ping time over the GigE LAN.

The wifi router is about 20 feet away from me now, through a couple of uninsulated 2x4 and gypsum board walls; the WLAN is quiet at the moment, too. You speak of education, which suggests much longer distances between WAPs, rebar-reinforced cinder block walls, and dozens of other users on each WLAN channel. You might be lucky to get even my 36 Mbit/sec result.

I still think wireless HDMI will give a better user experience.

On Jan 19, 2016, at 9:11 AM, Joey forum@r5d.de wrote:

i stream the screen of the 2. monitor with ffmpeg / ffserver

That’s an inherently problematic way of approaching the problem.

Wifi is a terrible medium for transmitting live video, or in fact any realtime data. It’s subject to frequent timeouts, which are fine for web pages or email, where most of your time is spent reading what you downloaded, not pulling live data. And, a bit of delay is fine there, too.

The common solutions to that problem, used by the likes of YouTube and Netfix, are high compression rates and buffering. Neither solution is really open to you here.

First, high compression rates take too much CPU. (Just curious: what codec and encoding parameters are you currently using?)

Second, the lag from buffering directly fights your wish for a realtime solution. You really don’t want lags of half a second or more between mouse movements and the resulting action appearing on the projector. And half a second of buffering is on the short side of typical for such applications. Wifi security camera buffering is often more like 3 seconds, for example.

Even when all of this works, your single stream will suck up a huge chunk of the whole network’s capacity, since wifi is inherently a broadcast medium. You might be nearly monopolizing it, in many cases. (e.g. 802.11g with “54” Mbit/sec, which ends up maybe 11 Mbit/sec at the computers, which is about the data rate you should be using for screen-res video.)

If I had this problem, I’d just use a wireless HDMI transceiver pair:

https://www.google.com/webhp?q=wireless%20hdmi

Then you’re not fighting for bandwidth with other wifi users, and it’s going to be geared for near-instant transmission.

Plus, the transceiver pair is smaller and cheaper than the second notebook. :)