The transcoding failed at first try for all resolutions for the files Politparade.webm and Genderwahn.webm. But after a few days was successful for all resolutions up to FullHD, but never succeded for VP9 QHD and UHD.
Maybe the trancoding only runs into a timeout, as it would probably take 10 hours or more?
I presume it's about https://commons.wikimedia.org/wiki/File:Politparade.webm and https://commons.wikimedia.org/wiki/File:Genderwahn.webm. I've requeued the transcodes manually (any autoconfirmed user is able to do it), let's see if it errors out again.
Just saw that the transcoding is now at 42 minutes, and while looking at it, came about this thought: the files are 4GiB (to the byte) each. Maybe the transcoded versions are exceeding the 4GiB file system limit?
I suspect it's the file size limit yes -- ffmpeg seems to be exiting with SIGXFSZ (signal 25, exit code 153) which means 'exceeded file size'. This is probably not the file system limit, but the resource limit applied to the transcode process? However transcodes going over 4 GB may have trouble being stored anyway. :(
We need to do some further infrastructure work to support very large video files...