Trasparency on background

Is there a way to have the background transparent, in order to use it with atem mini as secondary screen? with croma key any time i change the video source the primary key on atem mini goes off

When you set up the chroma screen in the Atem mini, there is a setting to allow you to choose whether it is persistent when you change the input or not.

Which is this setting? May you screen it?

Unfortunately, our ATEM mini died and I replaced it with a similar device from another manufacturer, so I no longer have the full details of what we set up. However, if you look in the manual, you will find all the information I used to set it up in the first place.

You will need to have the ATEM Software Control available (see page 26 of the manual). The instructions about the Luma key start on page 100, while the instructions about the Chroma key start on page 102 and continue through to page 107. You may also find the next section, which presents how to set up picture in picture (ideal for showing a PowerPoint overlaid on the live video of the speaker) very useful too.

I have also found an on-line version of the manual at https://usermanual.com/support/blackmagicdesign/web-manual/atem-mini/keying-using-atem-mini, which has the same information.