ddot-cli

One of my favorite open datasets is Washington DC's open traffic cameras. They have a funky architecture, which you can reverse engineer from viewing DevTools network table for https://www.dctrafficinfo.org/

I wanted to get some reps in with BubbleTea, so here's a CLI that lets you browse all available CCTV cameras.

Running

Be sure you have ffplay installed. On macOS, just run

brew install ffplay

Build the binary and run it:

go run cmd/ddotcli.go

DDOT Architecture

DDOT hosts a MQTT instance on AWS. By looking at the WebSocket messages, you can see that

• The credentials are passed in plaintext, username dcdot and password cctvddotpublic
• The MQTT broker has a topic DDOT/Cameras that, when you connect, will dump a gigantic JSON blob with data for all registered cameras
• There are various other topics but I don't currently use them. Things like DDOT/Incidents, DDOT/AVL, DDOT/PavementSensors... there's a lot here

Each camera has an HLS playlist that lets you tap into its live stream. I'm just shelling out to ffplay to do this in the CLI, but you can also transcode and record the stream, etc.

TODO

• Add command for recording the stream to disk
• Add command for running object detection over frames in the stream