RTCBot

RTCBot's purpose is to provide a set of simple modules that help in developing remote-controlled robots in Python, with a focus on the Raspberry Pi.

The documentation includes tutorials that guide in developing your robot, starting from a basic connection between a Raspberry Pi and Browser, and encompass creating a video-streaming robot controlled entirely over a 4G mobile connection, all the way to a powerful system that offloads complex computation to a desktop PC in real-time.

All communication happens through WebRTC, using Python 3's asyncio and the wonderful aiortc library, meaning that your robot can be controlled with low latency both from the browser and through Python, even when it is not connected to your local network.

The library is explained piece by piece in the documentation.

See Documentation & Tutorials

Installing

RTCBot relies on some Python libraries that will need to be compiled by pip, so you need to install their dependencies. The following commands will work on Ubuntu and Raspbian Buster:

sudo apt-get install build-essential python3-numpy python3-cffi python3-aiohttp \
        libavformat-dev libavcodec-dev libavdevice-dev libavutil-dev \
        libswscale-dev libswresample-dev libavfilter-dev libopus-dev \
        libvpx-dev pkg-config libsrtp2-dev python3-opencv pulseaudio

And then install rtcbot:

sudo pip3 install rtcbot

For installation instructions for Windows and Mac, refer to the documentation

Example

This example uses RTCBot to live stream a webcam to the browser. For details, please look at the tutorials.

Python code that streams video to the browser:

from aiohttp import web
routes = web.RouteTableDef()

from rtcbot import RTCConnection, getRTCBotJS, CVCamera

camera = CVCamera()
# For this example, we use just one global connection
conn = RTCConnection()
conn.video.putSubscription(camera)

# Serve the RTCBot javascript library at /rtcbot.js
@routes.get("/rtcbot.js")
async def rtcbotjs(request):
    return web.Response(content_type="application/javascript", text=getRTCBotJS())

# This sets up the connection
@routes.post("/connect")
async def connect(request):
    clientOffer = await request.json()
    serverResponse = await conn.getLocalDescription(clientOffer)
    return web.json_response(serverResponse)

@routes.get("/")
async def index(request):
    with open("index.html", "r") as f:
        return web.Response(content_type="text/html", text=f.read())

async def cleanup(app=None):
    await conn.close()
    camera.close()

app = web.Application()
app.add_routes(routes)
app.on_shutdown.append(cleanup)
web.run_app(app)

Browser code (index.html) that displays the video stream:

<html>
  <head>
    <title>RTCBot: Video</title>
    <script src="/rtcbot.js"></script>
  </head>
  <body style="text-align: center;padding-top: 30px;">
    <video autoplay playsinline></video> <audio autoplay></audio>
    <p>
      Open the browser's developer tools to see console messages (CTRL+SHIFT+C)
    </p>
    <script>
      var conn = new rtcbot.RTCConnection();

      conn.video.subscribe(function (stream) {
        document.querySelector("video").srcObject = stream;
      });

      async function connect() {
        let offer = await conn.getLocalDescription();

        // POST the information to /connect
        let response = await fetch("/connect", {
          method: "POST",
          cache: "no-cache",
          body: JSON.stringify(offer),
        });

        await conn.setRemoteDescription(await response.json());

        console.log("Ready!");
      }
      connect();
    </script>
  </body>
</html>

Development

To use rtcbot code directly, clone the repository, and install the requirements:

pip install -r requirements.txt

Then, you will need to perform the javascript build step, to prepare the browser code. This step requires both make and npm to be installed on your machine. To build the javascript, type in:

make js

This creates rtcbot/rtcbot.js, which is returned by rtcbot.getRTCBotJS().

After these two steps, you should be able to successfully import and use the library.