The cause is a conflict between required libavformat and ffmpeg from RPMFusion on Fedora.
$ sudo dnf install libavformat-free-devel
Updating and loading repositories:
Repositories loaded.
Failed to resolve the transaction:
Problem: package libavformat-free-devel-7.1.2-2.fc43.i686 from fedora requires libavformat-free(x86-32) = 7.1.2-2.fc43, but none of the providers can be installed
- conflicting requests
- libavformat-free-7.1.2-2.fc43.i686 from fedora has inferior architecture
- package libavformat-free-devel-7.1.2-2.fc43.x86_64 from fedora requires libavformat-free(x86-64) = 7.1.2-2.fc43, but none of the providers can be installed
- problem with installed package
- installed package ffmpeg-libs-7.1.4-1.fc43.x86_64 conflicts with libavformat-free provided by libavformat-free-7.1.2-2.fc43.x86_64 from fedora
- package ffmpeg-libs-7.1.2-7.fc43.x86_64 from rpmfusion-free conflicts with libavformat-free provided by libavformat-free-7.1.2-2.fc43.x86_64 from fedora
- package ffmpeg-libs-7.1.4-1.fc43.x86_64 from rpmfusion-free-updates conflicts with libavformat-free provided by libavformat-free-7.1.2-2.fc43.x86_64 from fedora
- package libavformat-free-devel-7.1.4-1.fc43.i686 from updates requires libavformat-free(x86-32) = 7.1.4-1.fc43, but none of the providers can be installed
- libavformat-free-7.1.4-1.fc43.i686 from updates has inferior architecture
- package libavformat-free-devel-7.1.4-1.fc43.x86_64 from updates requires libavformat-free(x86-64) = 7.1.4-1.fc43, but none of the providers can be installed
- installed package ffmpeg-libs-7.1.4-1.fc43.x86_64 conflicts with libavformat-free provided by libavformat-free-7.1.4-1.fc43.x86_64 from updates
- package ffmpeg-libs-7.1.2-7.fc43.x86_64 from rpmfusion-free conflicts with libavformat-free provided by libavformat-free-7.1.4-1.fc43.x86_64 from updates
- package ffmpeg-libs-7.1.4-1.fc43.x86_64 from rpmfusion-free-updates conflicts with libavformat-free provided by libavformat-free-7.1.4-1.fc43.x86_64 from updates
You can try to add to command line:
--allowerasing to allow removing of installed packages to resolve problems
--skip-broken to skip uninstallable packages