This is too easy to handle. You mean that both halls have broadcasting equipment, so you want to transmit the camera signal of the master of ceremonies in the main hall to the auxiliary hall. Just buy the AV cable directly. Of course, the AV cable is not the best choice of quality, but the price is the most acceptable, which is available on Taobao.

Any camera has AV output. For example, Sony 1000C/ Panasonic MD series can directly use AV head (AV head is the kind of head inserted behind DVD, which is universal), and some use 3.5 interface (this is almost the case with shoulder-mounted machine).

You don't care what interface the camera is, just make sure that the other party has a patch cord, and the AV cable is the best one, just two.

Generally, the main hall directly watches the scene, and there is no TV. It doesn't matter whether there is a TV or not, just put an AV line on it. All playback devices (TV, projector, LED, etc. ) absolutely supports AV video.

Any kind of line will lose when it grows. As for the line loss, I have seen the normal use of 190P plus 100 meters of AV lines. Of course, the wire is better and the loss is less.