(EN) Display screens of a virtualized classroom

The first thing to emphasize is that from Aules we CANNOT recommend a type of monitor with specific characteristics. It is not a strictly technical decision, since multiple factors must be taken into account, including user preferences and the existence of affordable models in the market.

The size of a screen (in inches) is closely related to the proportions of height and width of the screen (aspect ratio). Currently, the most common format is the 16: 9 panoramic, which has displaced the traditional 4: 3 of the old monitors.

In addition, the native (optimal) resolution of a monitor must be taken into account, that is, the number of dots or pixels that the monitor is wide and tall. Each monitor is designed to show, preferably, its optimal resolution (which usually coincides with its maximum resolution). To display other resolutions, the monitor must perform an operation called rescaling. In general with a rescaled resolution, the image quality is worse, especially in texts, than with a native resolution.

The size of a monitor is an independent specification, which is not affected at all by its resolution. For this reason you can find relatively small screens with very high resolutions.

The thing is complicated in virtualized computer classrooms where the teacher's computer has a monitor and a projector connected via a video splitter (2-way splitter and one input). In these cases we must keep in mind that:

• The video splitter is a device that takes the video signal from a computer and replicates it on several display screens. This means that all devices connected to the splitter have the same resolution and aspect ratio, for this reason it is possible that the image shown on the monitor is suitable for the size of the monitor but looks small or deformed on the projector or vice versa, that it looks good on the projector and not on the monitor.

• It is recommended that, in a classroom, the monitor, the projector and the projection screen have the same aspect ratio.

• CentOS selects as the display screen the device that is connected to the main output of the splitter, therefore, the screen resolution (The screen resolution in CentOS is by default, the optimal resolution) and the aspect ratio is defined by the characteristics of the device connected to this output.

• On the CentOS 7 desktop we have a launcher (icon) called “Screens” that is used to launch the utility that allows us to adjust the screen resolution during our session.

• On the CentOS 6.8 desktop we can access the preferences of the screen by clicking on the drop-down menu (located on the top bar of the desktop) called “System” and choosing the option “Preferències” => “Screens”.

• CentOS does not save the configuration changes that a user makes and when another user logs in, the computer is restarted or the computer is turned off, these changes are lost.

• The screen resolution in virtualized Windows desktops is the same as the screen resolution and aspect ratio selected in CentOS.