Since upgrading to DO12 I enabled the "Description" column in displayed fields of my listers.
If I have a tab open to a SMB share containing several hundred movie files, DO gobbles up all the available memory (~4GB) and crashes while trying to process the description field for each movie in the directory.
Removing the "Description" from my displayed fields stops the run-away memory consumption. Perhaps DO should only attempt to process file descriptions for the files that I currently visible in the lister.
The description column itself should only use as much memory as is needed to store the strings it displays. That is usually very little memory, and will be freed when you close the window or change folders.
But generating those strings involves calling into video demuxers/decoders, which sometimes have memory leaks or other problems (sometimes only with certain files or types of files that are formatted in a way they don't expect). If the memory isn't being freed when you close the window then it's likely that the DLLs which handle the movie format in question are causing the leak.
It's possible the leak is in Opus itself, but if it is we'd be likely to see it all the time. Video demuxers/decoders have a long history of problems as well (due to the complexity of the formats they deal with, and the variety of encoders which all do things slightly differently).
If you can find a small video file that triggers the leak and point us to a copy of it, we can try to reproduce what you're seeing and check whether the leak is in Opus itself or in the DLLs outside of our control. If it's in the DLLs then the only option is install alternative demuxer/decoder DLLs or report the bug to the vendor (Microsoft by the look of the stack trace) and hope for an update.