Build an app for android and ios

I need an app that does two functions at the same time. The first is that it allows the user to send and receive messages through a chat system using Google's firebase. And the second is that it allows the user to stream video and audio in real time to a given rtmp server. (I already have the server, the application would only need the rtmp address where to send the video, that address must be able to be changed at will through a text box). Regarding visual issues, I want the chat to be visualized on the video that is being transmitted, simulating the behavior of a live on instagram or on tik tok. The chat will only be between two people, it will not be a group. and to access the application, the user need to place a name and a password that must already be specified in a database in the firebase, the user cannot be registered in the application. I would prefer the use of the flutter environment as I want the app to work for IOs and Android and to be able to use it in landscape mode.