I was able to successfully compile & import ffmpeg into my existing iOS app. However now I want to ru the following commands to clip and crop a video. How do I interact with the ffmpeg library from iOS?

This command words for me via command line:

```
./ffmpeg -i input.mp4 -ss 157 -t 10 -vf crop=250:250:200:100 -strict -2 clipped.mp4

```