Write filename to tag, but only where there is no tag info already

I am trying to figure out how to do a large batch where the file name (artist - title) is written to the tag BUT SKIPPING any tag fields that are already populated (ie. write only empty ones).

Apologies I am a newby, if this is a common question I may not be using the right search terms to find this topic. And I just updated the client and after teaching myself a few simple steps yesterday the update does things pretty differently. Didn't the prior version have a preview function?

..so any help appreciated.

Mike

Which could these "things" be?
Anyway: you would have to filter for the missing fields and then update only those.
On the other hand: if the data in the filenames is better than the tag data (how could that happen?) then import whatever is there and you probably will not see any difference.

The import of just 2 fields would require only 2 filters - anything more complex with $if() and user-defined fields would require much more effort.

Where were you looking for a preview?
Which version do you use?

You could use the action Guess values to write the filename to temporary fields e.g. TEMPARTIST and TEMPTITLE and then use the action Format value:

Field: ARTIST

String: $if2(%artist%,%tempartist%)

plus another one for TITLE and then delete the temp tags. All this can be done within an Action group.

Thank you folks. I think I am not even at a level to make good use of your comments, I will have to spend more time with the program, and then come back to what you are suggesting. Thank you!

You could try a simple approach:
Enter as filter
%artist% MISSING
(the filter box is at the botton)
Now you will see all the files that have nothing in the field ARTIST.
Select the files
Open Convert>Filename-Tag, enter as mask:
%artist% - %dummy%
This will use only the front bit of the filename and put it into ARTIST
Now use the filter again, only this time with
%title% MISSING
Then open Convert>Filename-Tag, enter as mask:
%dummy% - %title%
and this should fill the TITLE with data from the filename.

Thanks Ohrenkino, I hope to report back after I am competent enough with MP3TAG to actually put all this advice to use