Per SDB:Firefox MP4/H.264 Video Support - openSUSE Wiki,
zypper install libavcodec56 libavcodec57 libavcodec58 libavformat56 libavformat57 libavformat58 libavdevice56 libavdevice57 libavdevice58
produces
Loading repository data...
Reading installed packages...
'libavcodec57' is already installed.
No update candidate for 'libavcodec57-3.4.9-1.58.x86_64'. The highest available version is already installed.
'libavdevice57' is already installed.
No update candidate for 'libavdevice57-3.4.9-1.58.x86_64'. The highest available version is already installed.
'libavformat57' is already installed.
No update candidate for 'libavformat57-3.4.9-1.58.x86_64'. The highest available version is already installed.
'libavcodec58' not found in package names. Trying capabilities.
No provider of 'libavcodec58' found.
'libavdevice58' not found in package names. Trying capabilities.
No provider of 'libavdevice58' found.
'libavformat58' not found in package names. Trying capabilities.
No provider of 'libavformat58' found.
Resolving package dependencies...
The following 9 NEW packages are going to be installed:
libavcodec56 libavdevice56 libavfilter5 libavformat56 libavresample2 libavutil54 libpostproc53 libswresample1 libswscale3
9 new packages to install.
Overall download size: 5.7 MiB. Already cached: 0 B. After the operation, additional 14.1 MiB will be used.
Continue? [y/n/v/...? shows all options] (y): y
Retrieving: libavutil54-2.8.18-1.50.x86_64 (Packman Repository) (1/9), 206.1 KiB
Retrieving: libavutil54-2.8.18-1.50.x86_64.rpm ..........................................................................................................................................................................[done (14.8 KiB/s)]
Retrieving: libavresample2-2.8.18-1.50.x86_64 (Packman Repository) (2/9), 55.7 KiB
Retrieving: libavresample2-2.8.18-1.50.x86_64.rpm ....................................................................................................................................................................................[done]
Retrieving: libswscale3-2.8.18-1.50.x86_64 (Packman Repository) (3/9), 154.2 KiB
Retrieving: libswscale3-2.8.18-1.50.x86_64.rpm .........................................................................................................................................................................[done (103.2 KiB/s)]
Retrieving: libswresample1-2.8.18-1.50.x86_64 (Packman Repository) (4/9), 54.1 KiB
Retrieving: libswresample1-2.8.18-1.50.x86_64.rpm ....................................................................................................................................................................................[done]
Retrieving: libpostproc53-2.8.18-1.50.x86_64 (Packman Repository) (5/9), 50.4 KiB
Retrieving: libpostproc53-2.8.18-1.50.x86_64.rpm .....................................................................................................................................................................................[done]
Retrieving: libavcodec56-2.8.18-1.50.x86_64 (Packman Repository) (6/9), 3.8 MiB
Retrieving: libavcodec56-2.8.18-1.50.x86_64.rpm ..........................................................................................................................................................................[done (3.4 MiB/s)]
Retrieving: libavformat56-2.8.18-1.50.x86_64 (Packman Repository) (7/9), 790.9 KiB
Retrieving: libavformat56-2.8.18-1.50.x86_64.rpm .......................................................................................................................................................................[done (542.3 KiB/s)]
Retrieving: libavfilter5-2.8.18-1.50.x86_64 (Packman Repository) (8/9), 519.0 KiB
Retrieving: libavfilter5-2.8.18-1.50.x86_64.rpm ........................................................................................................................................................................[done (460.8 KiB/s)]
Retrieving: libavdevice56-2.8.18-1.50.x86_64 (Packman Repository) (9/9), 61.9 KiB
Retrieving: libavdevice56-2.8.18-1.50.x86_64.rpm .....................................................................................................................................................................................[done]
Checking for file conflicts: .........................................................................................................................................................................................................[done]
(1/9) Installing: libavutil54-2.8.18-1.50.x86_64 .....................................................................................................................................................................................[done]
(2/9) Installing: libavresample2-2.8.18-1.50.x86_64 ..................................................................................................................................................................................[done]
(3/9) Installing: libswscale3-2.8.18-1.50.x86_64 .....................................................................................................................................................................................[done]
(4/9) Installing: libswresample1-2.8.18-1.50.x86_64 ..................................................................................................................................................................................[done]
(5/9) Installing: libpostproc53-2.8.18-1.50.x86_64 ...................................................................................................................................................................................[done]
(6/9) Installing: libavcodec56-2.8.18-1.50.x86_64 ....................................................................................................................................................................................[done]
(7/9) Installing: libavformat56-2.8.18-1.50.x86_64 ...................................................................................................................................................................................[done]
(8/9) Installing: libavfilter5-2.8.18-1.50.x86_64 ....................................................................................................................................................................................[done]
(9/9) Installing: libavdevice56-2.8.18-1.50.x86_64 ...................................................................................................................................................................................[done]
Installation has completed with error.
beedell:~ #
of which the important part is
Installation has completed with error.
Is acquisition of a specific description of the error possible, and before that, does this alone indicate serious problemacy?