mediamtx: substitute hostname/IP before start

os/mediamtx/justfile

@@ -8,7 +8,6 @@ setup:
     sudo cp mediamtx.service /etc/systemd/system/
     sudo cp mediamtx.yaml /etc/mediamtx.yaml
     sudo chown pi:pi /etc/mediamtx.yaml
-    sudo node ../../lib/mediamtx.js
     sudo systemctl reenable mediamtx
     sudo systemctl restart mediamtx
 

os/mediamtx/mediamtx.service

@@ -1,10 +1,14 @@
 # https://mediamtx.org/docs/usage/start-on-boot#linux
 
 [Unit]
-After=network.target
-Wants=network.target
+After=network-online.target
+Wants=network-online.target
 
 [Service]
+# The hostname/IP substitution into /etc/mediamtx.yaml is driven by the
+# `runOnInit` hook in the YAML itself (see os/mediamtx/mediamtx.yaml), so it
+# also runs when mediamtx is started outside systemd (e.g. `just dev`).
+# network-online.target is kept so the wired IP is available when that runs.
 ExecStart=/usr/local/bin/mediamtx /etc/mediamtx.yaml
 
 [Install]

os/mediamtx/mediamtx.yaml

@@ -37,3 +37,8 @@ paths:
     alwaysAvailable: true
     alwaysAvailableTracks:
       - codec: H264
+    # Rewrite this file's placeholder hostname/IP (above) with the device's real
+    # values at startup, so WebRTC ICE candidates resolve regardless of how
+    # mediamtx was launched (systemd, `just dev`, manual). mediamtx watches the
+    # config file and hot-reloads after the rewrite. See lib/mediamtx.js.
+    runOnInit: /usr/bin/node /opt/PlanktoScope/lib/mediamtx.js