I wrote this tool to extract metadata which I couldn't extract using either the metadata extractor supplied with jAlbum or ffmpeg. The tool uses the excellent exiftool utility (https://exiftool.org/). You would need to download a copy of exiftool.exe and place it in the 'bin' subfolder of the config folder (ctrl-shift-C), where ffmpeg.exe resides. Alternatively, for each skin on which you wish to use the tool, create a user variable called exiftool with a value specifying the location of the file (path + filename).
If you run the tool as it is, it will do nothing. You need to change the settings. If you open the tool in a text editor, you will see comments explaining how to do this. You can specify which metadata fields you want to extract and whether you want to use the extracted data for comments, title or keywords. Different metadata can be concatenated, and alternative metadata sources can be specified in case a particular one is not present. The metadata field names used in the settings should correspond to the short field names you get if you run exiftool with the -s option. GPS data can also be extracted and used.
There are different settings for images and videos, reflecting the differing capabilities of the normal jAlbum metadata extractor.
The tool allows you to choose whether to run it on the entire album, or on just selected files/folders. If a folder is selected the tool will run on 'descendant' subfolders also.
I am currently using the tool for three separate purposes:
(a) I have lots of photos in which I have tagged people (using Picasa). The tool extracts a comma separated list of these names (from the RegionName field) and adds each to the image's keywords, allowing me to search for images by the name of the person. There might be a different way of doing this in jAlbum but if so I haven't found it.
(b) I have populated video metadata fields with the local time of creation and I use the tool to create comments including this data (not otherwise readable by the metadata extractor) plus additional data.
(c) I use the tool for getting GPS data from videos, though if this is all I wanted I could have instead used RobM's excellent tool (https://jalbum.net/forum/thread.jspa?threadID=54566&tstart=0).
Please use at your own risk. (I have tried to minimise possible damage by temporarily turning off the Write XMP option, if it is set, while the tool is running.)
Well this is embarrassing. Some last minute changes before posting the tool introduced a big bug that slipped past the final testing but prevented the tool from working on individually selected images. Now fixed.