FFmpeg 3.3.4 avfoundation to record only a specific section of the screen on macOS Sierra using the command line

Question

I\'m using FFmpeg version 3.3.4 (installed via brew) through the command line to record my desktop during some automated tests on my macOS Sierra (10.12.6).

I would

Answer 1

First you need to find the name of the AVFoundation device that corresponds to your screen:

ffmpeg -hide_banner -f avfoundation -list_devices true -i ""

[AVFoundation input device @ 0x7fc1cd40ec60] AVFoundation video devices:
[AVFoundation input device @ 0x7fc1cd40ec60] [0] HD Pro Webcam C920
[AVFoundation input device @ 0x7fc1cd40ec60] [1] FaceTime HD Camera (Built-in)
[AVFoundation input device @ 0x7fc1cd40ec60] [2] Capture screen 0
[AVFoundation input device @ 0x7fc1cd40ec60] AVFoundation audio devices:
[AVFoundation input device @ 0x7fc1cd40ec60] [0] HD Pro Webcam C920
[AVFoundation input device @ 0x7fc1cd40ec60] [1] Built-in Microphone

So my screen is device [2] because I have two cameras attached and they are devices [0] and [1].

Then, as you are on a Mac, you will probably want to use QuickTime to view videos, so you need to ensure you make videos that are compatible - that means using -pix_fmt yuv420p.

ffmpeg -f avfoundation -i "2:0" -vf  "crop=1024:768:400:800" -pix_fmt yuv420p -y -r 10 out.mov

The 1024x768 are the width and height of the video, and the 400:800 are the offset from top-left of screen that I want to record from.