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
22 thoughts on - Monitor Dummy Device
What is a dual screen solution without a second monitor? Are you talking about virtual desktops?
Am 2016-01-17 17:47, schrieb SternData:
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”
Am 2016-01-17 18:09, schrieb SternData:
But this means other things. i think i need a virtual device for dual screen using.
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.
thx for this tricky idea! Unfortunately i need it for notebooks ..
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.
—
Mark Haney ::: Senior Systems Engineer
*VIF* International Education P.O. Box 3566 ::: Chapel Hill, N.C. 27515 ::: USA
919-265-5006 office
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:
Could you use Xephyr (xorg-x11-server-Xephyr package in CentOS7) as a nested X environment for the streaming screen?
IIRC, back when I did presentations regularly there was a way to screen share a second virtual desktop and leave the primary on the display itself. But that was 5 years ago and I”ve slept since then.
—
Mark Haney ::: Senior Systems Engineer
*VIF* International Education P.O. Box 3566 ::: Chapel Hill, N.C. 27515 ::: USA
919-265-5006 office
Am 2016-01-19 20:28, schrieb Jonathan Billings:
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.
:-)
Am 20.01.2016 um 15:07 schrieb Jonathan Billings:
Joey wrote:
You walk around with a laptop during a presentation?
mark
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.
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:
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.
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:
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:
“Xdmx is proxy X server that provides multi-head support for multiple displays attached to different machines (each of which is running a typical X server). When Xinerama is used with Xdmx, the multiple displays on multiple machines are presented to the user as a single unified screen.”
—
Jonathan Billings
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 2×4 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.
22 thoughts on - Monitor Dummy Device
What is a dual screen solution without a second monitor? Are you talking about virtual desktops?
Am 2016-01-17 17:47, schrieb SternData:
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”
Am 2016-01-17 18:09, schrieb SternData:
But this means other things. i think i need a virtual device for dual screen using.
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.
—
_
°v°
/(_)\
^ ^ Mark LaPierre Registered Linux user No #267004
https://linuxcounter.net/
****
Am 2016-01-19 02:01, schrieb Mark LaPierre:
Hey,
thx for this tricky idea! Unfortunately i need it for notebooks ..
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.
—
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. http://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!
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:
Could you use Xephyr (xorg-x11-server-Xephyr package in CentOS7) as a nested X environment for the streaming screen?
IIRC, back when I did presentations regularly there was a way to screen share a second virtual desktop and leave the primary on the display itself. But that was 5 years ago and I”ve slept since then.
—
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. http://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!
Am 2016-01-19 20:28, schrieb Jonathan Billings:
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.
:-)
Am 20.01.2016 um 15:07 schrieb Jonathan Billings:
Joey wrote:
You walk around with a laptop during a presentation?
mark
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:
So how would a second, virtual display help?
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:
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.
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:
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. :)
This is why I suggested Xdmx. Please check out the documentation:
http://dmx.sourceforge.net/
“Xdmx is proxy X server that provides multi-head support for multiple displays attached to different machines (each of which is running a typical X server). When Xinerama is used with Xdmx, the multiple displays on multiple machines are presented to the user as a single unified screen.”
—
Jonathan Billings
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 2×4 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.