Step One

gistfile1.cs

//we are planning to use filter concatenation on three input videos
var filterchain = Filterchain.FilterTo<VideoStream>(new Concat()); 

//we want our output to be encoded using the following settings:
// -c:v libx264
// -b:v 3000k
// -s 852x480
// -y 
var settings = SettingsCollection.ForOutput(
  new CodecVideo("libx264"), 
  new BitRateVideo(3000), 
  new Size(852, 480), 
  new OverwriteOutput());