[FFmpeg-user] How can I stream to a Mac Mini USB output?

[Fred Rotbart]

Hi,

I have a MiniDSP U-DIO8 
<https://www.minidsp.com/products/usb-audio-interface/u-dio8> connected 
to the USB port of a 2018 Mac Mini running Kodi 18.1-RC1 on Mojave 
10.14.4. The U-DIO8 provides 8 output channels as 4xSPDIF connections 
and similarly 8 channels of input as 4xSPDIF connections.

I can capture audio input from the input channels but I do not know how 
I can stream ffmpeg output to the U-DIO8 output channels.

If I list devices this is what I get:

~#ffmpeg -f avfoundation -list_devices true -i ""
ffmpeg version 4.0 Copyright (c) 2000-2018 the FFmpeg developers
   built with clang version 4.0.1 (tags/RELEASE_401/final)
   configuration: --prefix=/Users/fred/anaconda 
--cc=x86_64-apple-darwin13.4.0-clang --disable-doc --enable-shared 
--enable-static --enable-zlib --enable-pic --enable-gpl 
--enable-version3 --disable-nonfree --enable-hardcoded-tables 
--enable-avresample --enable-libfreetype --disable-openssl 
--disable-gnutls --enable-libvpx --enable-pthreads --enable-libopus 
--enable-postproc --disable-libx264
   libavutil      56. 14.100 / 56. 14.100
   libavcodec     58. 18.100 / 58. 18.100
   libavformat    58. 12.100 / 58. 12.100
   libavdevice    58.  3.100 / 58.  3.100
   libavfilter     7. 16.100 /  7. 16.100
   libavresample   4.  0.  0 /  4.  0.  0
   libswscale      5.  1.100 /  5.  1.100
   libswresample   3.  1.100 /  3.  1.100
   libpostproc    55.  1.100 / 55.  1.100
[AVFoundation input device @ 0x7f8ee6c00540] AVFoundation video devices:
[AVFoundation input device @ 0x7f8ee6c00540] [0] FaceTime HD Camera
[AVFoundation input device @ 0x7f8ee6c00540] [1] Capture screen 0
[AVFoundation input device @ 0x7f8ee6c00540] AVFoundation audio devices:
[AVFoundation input device @ 0x7f8ee6c00540] [0] USBStreamer
[AVFoundation input device @ 0x7f8ee6c00540] [1] Built-in Microphone

The USBStreamer is the U-DIO8 device.

What do I need to add to the ffmpeg command line to cause ffmpeg to 
output to USBStreamer?

Thanks,
- Fred