iTunes has the ability to attempt to download missing artwork for audio files. Unfortunately you cannot add DFF, DSF or FLAC files to your iTunes library. Further, while iTunes can contain WAV files in its library it will not process artwork for WAV files.
These functions can be used as part of a workflow to get around this limitation.
This function is only valid stepwise and while batch processing.
First you run a batch process where the action contains a Create Stubs function. You specify which audio types you are interested in processing for missing artwork. (m4a, m4b, m4v and mp4 files all fall under MPEG-4). If a folder contains at least one audio file of a specified type, Yate will construct a small mp3 file, a stub, with one track's metadata. One stub file will be created for every unique album name. The created files will be added to iTunes and linkage information will be retained. Folders already containing stub files are ignored. Any albums already containing artwork are also ignored.
When the batch process completes, you can go to iTunes, select the produced stub files and from the context menu do a Get Album Artwork. If your metadata for Album and Artist matches with something in iTunes' extensive catalog, an artwork item will be downloaded. In order to make it easier to find the stub files, the Grouping field will have been set to STUB. The easiest way to locate the stub files in iTunes is to create a Smart Playlist which matches a Grouping field of STUB. Note that if you have enabled the iTunes-Preferences-Store-Automatically Download Album Artwork option, this step should take place automatically.
After attempting to download the missing artwork in iTunes you can run a second batch process containing a Process Stubs function. Yate will only process folders containing stub files. Each produced stub file retains the linkage to iTunes and the file types that you're interested in. Typically you want the function to extract artwork from iTunes, remove the stub files from iTunes and then to delete the stub files. You can pick any combination of these options if for any reason you want to clean things up without extracting artwork. Remember that the Batch Processing Wizard does not automatically save modified files. Either select Auto Save Files before starting the batch run or include a Save function in the action.
If no artwork for a particular stub file has been located, no tracks will be modified. Artwork will not be saved to files which already contain artwork. If you create the stub files, then manually add artwork to the the tracks, the Process Stub function will not modify the tracks.
These functions are intended to be used as a workflow. Do not edit the files after the Create Stubs batch run before you do the Process Stubs batch run.