Welcome at/in/on the meeting (when meeting is teleconference)

Hello, everyone.

I did the research and found out that we say:
a) at a meeting - suggests different location (off-site) than the speaker and/or less involvement
b) in a meeting - suggests the same location (on-site) and/or more involvement

However, I am not sure how to say "Welcome at/in/on [meeting name]..."
1) When everyone is in the same room (I incline to 'in').
2) When this meeting is a teleconference (or videoconference) between people being in different countries (maybe 'on' is possible here as an analogy with 'on a call'? But I have no idea really which is best here).

Could you please help me with the questions above?