This is quite recent, but I don't know exactly which version made this appear. Trying to play videos with mplayer or mpv fails now. It works with dragon, or vlc though. From a strace, they both die from SIGPIPE trying to write to STDOUT. Dolphin is 19.08.1 Operating System: Arch Linux KDE Plasma Version: 5.16.5 KDE Frameworks Version: 5.61.0 Qt Version: 5.13.0 Kernel Version: 4.19.69-1-lts OS Type: 64-bit Processors: 8 × Intel® Core™ i7-4790K CPU @ 4.00GHz Memory: 15,6 GiB of RAM
What happens if you try to open the apps directly, and then open the files from within the app? What happens if you try to open the files on the command-line by directly opening the app (e.g. `mpv /path/to/file.mp3`)? Is anything printed to the terminal window? What happens if you try to open the files on the command-line using `kioclient exec file:/path/to/file.mp3`? Is anything printed to the terminal window?
Seems the problem has disappeared. I had a few updates in packages these days, so maybe it was already solved. Closing...