Faced with this same problem, and upset with the available options, I started on a tool myself called [FFcommander](https://github.com/harper-rhett/FFCommander). It allows you to speak to FFmpeg with C# by sending command line commands. It has an API for common features that abstract the commands completely. I plan to expand it in the future to cover much more ground but for the time being it should be really easy to develop off of as well.