[SOLVED] Unable to install libav-tools, ffmpeg etc. on Stretch

[tempest]

I am suffering this same problem, but I am using the cubox-i. Is there a way to satisfy this using the firmware-imx package instead of the xbian-package-firmware?

edit: Forgive me, I didn't notice that this was marked as "solved". I will open a new thread for this related issue. I will also try not to post with a 3 year old climbing on me.