FLAC isn’t supported by iTunes, but you can definitively listen FLAC files on macos using other apps (VLC for example).
ALAC & FLAC are very similar, and lossless, you can easily convert from one to the other if needed.
About cover art, it all depends on the player, but basically you want to embed image in tags, and prolly create a file with cover art for each album folder (some players will display cover.jpg or folder.jpg images they find).
So… checking on my (not recently upgraded) Macbook…
QuickTime player 10.4 which comes with OSX 10.13 will play FLAC files, but does not read/display/understand any embedded metadata
QuickView, which is what you get when you press the spacebar in Finder, will play FLAC files, but does not read/display/etc. any embedded metadata.
When you “Add to Library…” with iTunes 184.108.40.206, it says: Oh yeah, that’s a FLAC file!.. and then completely ignores the FLAC file if you try to import it.
VLC, Audacity, Picard, etc. etc. will all read the FLAC file(s) just fine and display all the metadata just like you would expect literally anything and everything which can read a FLAC file would do… except for Apple’s half-assed FLAC support…
There’s an open source Quicklook plugin you can install which does FLAC better than Apple’s default handler. (I haven’t actually tried it out yet myself.) And… does anyone ever actually use QuickTime for anything?
I’ve heard that recent versions of IOS have native FLAC support now too… (Though maybe not the default IOS Music app?)
By “Support” I mean as a default in the system library that any program can just use with the same simple function call used to play every other audio format. Most dedicated music playing software will typically use it’s own built-in music playing code… because the default library that comes with most operating systems sucks. (Such as by not fully supporting FLAC, for example.)
So, I’m going to guess, that once upon a time, you had all your mp3s imported into iTunes, and then you went to the “File” menu, and you went to “Library”, and you clicked on “Get Album Artwork”… much like I did once myself… and it totally screwed up about 10% of all the cover art on your mp3s.
Yeah, iTunes does that… It’ll put the absolutely most random, bizarre, incorrect cover art on some of your albums/mp3s. (I think it’s doing some kind of fuzzy soundx sting match on the name of the album, only… and then using whatever the first returned result is.) I only use Picard now for adding cover art.
I recommend keeping your mp3s as mp3s. You don’t really gain any advantages by converting your mp3s into anything else. (Footnote: There are exceptionally rare circumstances when you may need to convert your files, for a very rare and specific use case… but just playing your music on a Mac is not one of those cases.) Keep your mp3s as mp3s.
After using Picard on my mp3 files I am pleased with the results, except for a few files that are apparently not found or clustered or something… out of about 5K mp3 files I am left with 16 for which MusicBrainz couldn’t find cover-art that I KNOW is displaying the wrong cover art. I can’t seem to find a way of simply deleting the incorrect embedded cover art being displayed.
First an apology to Paxapunch for another sidebar, you might appreciate it though.
I save everything to mp3 just because it’s so well known and further use will be some kind of listening, at most streaming to a player. The streaming server doesn’t need to transcode mp3 and thus it natively stays under any bandwidth consideration. Sophist, I used to rip everything to 320bitrate until I discovered VBR was of age. Funny thing, everything but classical consistently encodes at between 190 and 220. Classical, even string quartets are always above 300.
Thus ends my first post.