Port 554: RTSP
Port 554 is RTSP, the protocol most IP cameras use to stream live video.
What runs on port 554
RTSP servers listen on TCP 554 and let video players and recorders request a camera's live stream, at an address like rtsp://camera/stream1. The video itself usually travels over RTP. VLC and most NVR software can open RTSP streams directly.
On a home network
IP cameras, video doorbells, NVRs and DVRs from many brands serve RTSP on 554. Seeing it on a camera on your LAN is normal.
If port 554 is reachable from the internet
A camera with 554 reachable from the internet may let anyone watch the stream, especially if it has no password or a default one. Search engines like Shodan index large numbers of exposed camera streams. Cameras should reach you through the vendor app or a VPN, never through a forwarded 554.
How to check whether it is open on your network
Check your router's port forwarding and UPnP table for 554, and look at each camera's settings for RTSP authentication. RECON's Exposure Check shows whether 554 answers on your public address.
To find out whether port 554 is open on something in your home, and whether the internet can reach it, the app scans your Wi-Fi from your phone and checks your public address from the outside. It says what it checked and what it could not. Get RECON for iPhone — one-time purchase, no account, nothing leaves the device.