FFMpeg access AVFoundation usb subdevice camera on OSX Mojave

Question

I Have a dual USB camera for VR: two cameras, one usb connection. On linux, this appears in /dev/video0 and /dev/video1 and I can capture using ffmpeg -i /dev/video0

On Mojave, I can see both devices in the USB hub:

USB 2.0 Hub:

Product ID: 0x0101
Vendor ID:  0x1a40  (TERMINUS TECHNOLOGY INC.)
Version:    1.11
Speed:  Up to 480Mb/sec
Location ID:    0x14200000 / 8
Current Available (mA): 500
Current Required (mA):  100
Extra Operating Current (mA):   0

    Stereo Vision 2:

    Product ID: 0x9901
    Vendor ID:  0x0ac8  (Z-Star Microelectronics Corporation)
    Version:    27.02
    Serial Number:  SN0099
    Speed:  Up to 480Mb/sec
    Manufacturer:   SHENZHEN RERVISION TECHNOLOGY
    Location ID:    0x14220000 / 10
    Current Available (mA): 500
    Current Required (mA):  500
    Extra Operating Current (mA):   0

    Stereo Vision 2:

    Product ID: 0x9902
    Vendor ID:  0x0ac8  (Z-Star Microelectronics Corporation)
    Version:    27.02
    Serial Number:  SN0100
    Speed:  Up to 480Mb/sec
    Manufacturer:   SHENZHEN RERVISION TECHNOLOGY
    Location ID:    0x14210000 / 9
    Current Available (mA): 500
    Current Required (mA):  500
    Extra Operating Current (mA):   0

But when I list devices, I can see only one [0]:

ffmpeg -f avfoundation -list_devices true -i ""
    [AVFoundation input device @ 0x7fae5b501a80] AVFoundation video devices:
    [AVFoundation input device @ 0x7fae5b501a80] [0] Stereo Vision 2
    [AVFoundation input device @ 0x7fae5b501a80] [1] FaceTime HD Camera
    [AVFoundation input device @ 0x7fae5b501a80] [2] Capture screen 0

capturing from this device captures from one of the cameras.

How can I get ffmpeg to detect the second usb device as well?

Answer 1

I revisited this a year later. An update of ffmpeg caused both devices to be seen normally.

==> Upgrading 1 outdated package: 
ffmpeg 4.1.4_2 -> 4.3.1

..

ffmpeg -f avfoundation -list_devices true -i "" 

[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