AFAIK the snapshot prefix can only be a fixed string (i.e. no regular expressions), so not it cannot be done from with VLC. You can use sequential numbers instead of timestamps however, so the format would be PREFIX001.png, PREFIX002.png etc. (where PREFIX is your prefix).
Assuming you are using Windows (if you don't then a bash/shell script should work too) I thought I'd try writing a Batch script to see if could work, and it does (more or less):
Code: Select all
@echo OFF
cd "C:\Program Files\VideoLAN\VLC"
vlc --snapshot-prefix=%1- --snapshot-sequential %1
All that does is navigate to the VLC directory (the default being "C:\Program Files\VideoLAN\VLC"), and then runs VLC, setting the snapshot prefix to be "%1-" and enabling sequential numbers. %1 is the command on the next line, and so if you drag-and-drop a file onto the *.bat file the %1 will be the (complete) filename. Hence the format will be e.g. FILENAME-00001.png, FILENAME-00002.png etc.
So to try that out copy the text, put it in a text file, save it as a *.bat file and then drag and drop a file onto it. Then the snapshots should be named something like (if e.g. you input file is C:\Temp\File.avi):
C__Temp_File.avi-00001.png
Not ideal at it is the full file path, however a suggestion

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Cheers, Arite.