HTML5 canvas, node.js backend canvas, ffmpeg output

1. display webcam to HTML5 canvas
2.send canvas drawn data through websocket to node.js server
3. add text draw to each frames with nodebackend canvas
4. output every frames as a “Output.mp4” with ffmpeg
https://github.com/MuxLabs/wocket
this project already did 1, 2, 4. only need is add3.
please bid if you know nodebackend canvas and websocket, ffmpeg.