Seeing it on your PC
VLC or a camera app pulling a stream from a camera on your network uses 554.
Should you block it?
Fine on a local network. Cameras exposed to the internet on 554 are routinely found and watched by strangers, so keep them behind your router.
Check it on your PC
Run this in PowerShell to see what is using port 554 right now, and which program owns it:
Get-NetTCPConnection -LocalPort 554 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}Get-NetUDPEndpoint -LocalPort 554 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}No output means nothing is using the port at the moment. For every connection at once, paste netstat -ano into the netstat explainer.
Block it in Windows Firewall
In PowerShell run as administrator, this stops other computers from connecting to this port on your PC. It does not stop your own programs connecting out.
New-NetFirewallRule -DisplayName "Block inbound TCP 554" -Direction Inbound -Protocol TCP -LocalPort 554 -Action Block
New-NetFirewallRule -DisplayName "Block inbound UDP 554" -Direction Inbound -Protocol UDP -LocalPort 554 -Action Block
Undo it with Remove-NetFirewallRule -DisplayName "Block inbound …", using the same name. If you depend on the service on your local network, this rule stops that too.