Based on the MD5 lookup in Oli's script (thanks!), I've written a Python script that uses the eyeD3 module to find MP3s, look up the album artwork from Banshee's cache, and embed the artwork inside the MP3s. It skips any files that already have artwork embedded.

It's not perfect, but it worked on about 90% of my MP3s, and you can manually handle any exceptions using EasyTag. As it stands the script expects the MP3s to be two directory levels deep from the target directory (music root/artist/album). The script prints a report once it's done highlighting any files it couldn't process or for which it couldn't find artwork.

Obviously you need to install Python and the eyeD3 module to use it:

#! /usr/bin/env python



import os, sys, glob, eyeD3, hashlib



CACHE_FILE_PREFIX = os.getenv("HOME") + "/.cache/media-art/album-"



def embedAlbumArt(dir = "."):

    artworkNotFoundFiles = []

    errorEmbeddingFiles = []

    noMetadataFiles = []

    mp3s = findMP3Files(dir)



    for mp3 in mp3s:

        print "Processing %s" % mp3



        tag = eyeD3.Tag()

        hasMetadata = tag.link(mp3)



        if not hasMetadata:

            print "No Metadata - skipping."

            noMetadataFiles.append(mp3)

            continue



        if hasEmbeddedArtwork(tag):

            print "Artwork already embedded - skipping."

            continue



        artworkFilename = findAlbumArtworkFile(tag)



        if not artworkFilename:

            print "Couldn't find artwork file - skipping."

            artworkNotFoundFiles.append(mp3)

            continue



        print "Found artwork file: %s" % (artworkFilename)



        wasEmbedded = embedArtwork(tag, artworkFilename)



        if wasEmbedded:

            print "Done.

"

        else:

            print "Failed to embed.

"

            errorEmbeddingFiles.append(mp3)



    if artworkNotFoundFiles:

        print "

Artwork not found for:

"

        print "

".join(artworkNotFoundFiles)



    if errorEmbeddingFiles:

        print "

Error embedding artwork in:

"

        print "

".join(errorEmbeddingFiles)



    if noMetadataFiles:

        print "

No Metadata found for files:

"

        print "

".join(noMetadataFiles)



def findMP3Files(dir = "."):    

    pattern = "/".join([dir, "*/*", "*.mp3"])   

    mp3s = glob.glob(pattern)

    mp3s.sort()

    return mp3s



def hasEmbeddedArtwork(tag):

    return len(tag.getImages())



def findAlbumArtworkFile(tag):

    key = "%s	%s" % (tag.getArtist(), tag.getAlbum())

    md5 = getMD5Hash(key)

    filename = CACHE_FILE_PREFIX + md5 + ".jpg"

    if os.path.exists(filename):

        return filename

    else:

        return 0



def getMD5Hash(string):

    string = string.encode("utf-8")

    md5 = hashlib.md5()

    md5.update(string)

    return md5.hexdigest()



def embedArtwork(tag, artworkFilename):

    tag.addImage(eyeD3.ImageFrame.FRONT_COVER, artworkFilename)

    success = 0

    try:

        success = tag.update()

    except:

        success = 0

    return success



if __name__ == "__main__":

    if len(sys.argv) == 1:

        print "Usage: %s path" % (sys.argv[0])

    else:

        embedAlbumArt(sys.argv[1])