FFMpeg access AVFoundation usb subdevice camera on OSX Mojave
I revisited this a year later.  An update of ffmpeg caused both devices to be seen normally.
==&gt; Upgrading 1 outdated package: 
ffmpeg 4.1.4_2 -&gt; 4.3.1

..
ffmpeg -f avfoundation -list_devices true -i &quot;&quot; 

[AVFoundation indev @ 0x7f85b2e00380] AVFoundation video devices:
[AVFoundation indev @ 0x7f85b2e00380] [0] Stereo Vision 2 #2
[AVFoundation indev @ 0x7f85b2e00380] [1] Stereo Vision 2
[AVFoundation indev @ 0x7f85b2e00380] [2] FaceTime HD Camera
[AVFoundation indev @ 0x7f85b2e00380] [3] Capture screen 0