On CrossOver 17 and greater, the simplest solution to fix this issue is to run: /path/to/cxoffice/bin/cxfix missinggstreamer1libav missinggstreamer1libav.amd64
Or add --show-all to see how CrossOver would fix it on your platform and others.
Alternatively you may try one of the commands below.
For 32-bit Windows applications
32-bit Arch Linux : pacman -Syu gst-libav
Debian : apt-get install gstreamer1.0-libav:i386
For 64-bit Windows applications
Arch Linux : pacman -Syu gst-libav
Debian : apt-get install gstreamer1.0-libav:amd64
Neither Fedora nor openSUSE have the Libav GStreamer plugins.
The 64-bit Arch Linux does not have the 32-bit Libav GStreamer plugins.
cxfix --show-all may have more up-to-date fixes.
The commands usually also apply to derived distributions. So for instance a fix for Debian is typically also applicable to Ubuntu, Linux Mint, Deepin and Pop! OS. Similarly a fix for Fedora likely also works on Red Hat Enterprise Linux, CentOS, etc.
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