What is wrong with this code? Not working on Windows 10 / Ubuntu 14

Trying to convert a .gif to .mp4 :

var express = require('express');
var bodyParser = require('body-parser');
var app = express();
var ffmpeg = require('fluent-ffmpeg');  

var proc = new ffmpeg({ source: 'myfile.gif' })
  .withAspect('4:3')
  .withSize('640x480')
  .applyAutopadding(true, 'white')
  .saveToFile('myfile.avi', function(stdout, stderr) {
    console.log('file has been converted succesfully');
  });

app.listen(3000, function() {  
    console.log("Server Running on 3000");
});

Getting the same error on Windows 10 and Ubuntu 14 : Error: Cannot find ffmpeg.

What is wrong with the code? Please help.

via Somename