Synchronizing multiple Qt/QML Applications

msantoli

Hi,

I was thinking wether it was viable to have multiple Qt/QML applications ( possibly running on different computers ) synchronized together.
My idea was to have a videowall application, where each monitor was driven by a single computer ( embedded solution ), all rendering the same Qt/QML application but each rendering a different portion of it and all being synchronized together.
I really new to Qt/QML development and wanted to have some hints from the community.

Thanks
Massimo

SGaist

Hi and welcome to devnet,

You would have to use some form of IPC to keep things in sync. Since you have one computer per screen, a network solution is the most likely. Something using i.e. QTcpServer and QTcpSocket.

Hope it helps

msantoli

Thanks,
Definitely some kind of IPC has to be setup for keeping in sync the various computers. Before entering in the sync part I was also investigating wether it was possible to define different coordinate systems for each monitor. For example, if I have a setup with two 1280x720 monitors side by side ( horizontally) to achieve an virtual 2560x720 resolution, and then I have two qml files running on each computer. First computer is no problem since it has the drawing area 1280x720, on the second instead I would like to have the coordinate system translated by 1280 on the x-axis, so that it will start drawing from 1280 to 2560... I'm starting to experiment with the
transform: Translate { x: ... }
command... Wanted to know it you think this is the correct approach in changing the coordinate system.
My QML on the second monitor looks something like this:

Rectangle {
id: screen

width: 1280
height: 720

transform: Translate { x: -1280 }

...
...

}

The -1280 translation should achieve the nothing is drawn on the screen unless its x coordinate is > 1280.

Massimo

SGaist

This would then mean that each embedded computer will have the same qml file and only render a part of it ?

An alternative would be that each of your embedded systems would only act as screen like a multi-head computer setup (thin client comes to my mind but it's not exactly that). You main computer would then render one big qml file across all the screens connected.

msantoli

Yes the idea is to have the same qml file ( more or less - I'm still investigating if this is possible ) on each device and each device renders the part for its screen.
I think this is easily achievable when the qml has static parts and no animation. I trying to figure out how to make it work when you have animation, simple example: a square that moves horizontally from one to screen to the next...

In my example I have a timer that every second moves the rectangle of 10pixel to the right, to make everything work I need to have the two timers of the two devices synchronized... and this is what I'm trying to look in the sources of Qt....

Your idea could be a solution, do you think its feasible? The problem is that when you have a big videowall ( 3x3 or 4x4 ) I don't think a single computer has the power to render at a decent frame rate the whole setup..