title: How to add audio to video file at a specific time using ffmpeg
body: <p>I have an avi and a wav file. Let's suppose the video file is one hour long, and the audio file 30 minutes long and it's associated with the last 30 minutes of the video file.</p>
  
  <p>Is there a way to create a new video file with the video and audio combined but audio starting after the first 30 minutes of the video?</p>