title: How to create a MP4 video from scratch?
body: <p>I'm trying to write a service with Go that converts GIF to MP4.</p>
  
  <p>For GIF there's a builtin package "image/gif" which contains tools for decoding a GIF.</p>
  
  <p>But no such package exists for MP4.</p>
  
  <p>So I'm considering creating the MP4 file myself.</p>
  
  <p>After decoding a GIF, I have access to its images and parameters like delay, so if I figure out something like a "template for MP4 file", I can use these information to create one, right?</p>