Matching accuracy and Apple iTunes Match

Alex1 · July 17, 2020, 5:05pm

I’ll keep documenting my experience using Album ID in the list below, with a rating.

Rating = 1: Album ID is wrong or misleading
Rating = 2: Album ID is helpful
Rating = 3: Straightforward process from Album ID to UPC to selecting a release with confidence

Documentation of using Album ID

Whitney Houston feat. Faith Evans & Kelly Price
Heartbreak Hotel
Heartbreak Hotel (Hex Hector RIP Mix)
251090652, 1
Wrong Album ID (duration mismatch)

Yusef Lateef
The Gentle Giant
The Poor Fisherman
734113, 1
URL doesn’t redirect, a-tisket returns strange release year 1987 (link), UPC only found at mora.jp.

Ghazal
The Rain
[all tracks]
18310487, 3
Matched, though barcode (UPC) 044006662725 is missing

Willie Bobo
Verve//Remixed
Spanish Grease (Dorfmeister con Madrid de los Austrias Muga Reserva mix)
2091079, 1
Wrong Album ID (duration mismatch)

Astrud Gilberto
Verve//Remixed
Who Needs Forever? (Thievery Corporation remix)
4183088, 1
URL does not redirect

Dinah Washington
Verve//Remixed
Is You Is or Is You Ain’t My Baby? (Rae & Christian remix)
417693, 3
Matched

Nina Simone
Verve//Remixed
Feelin’ Good (Joe Claussell remix)
714237726, 1
URL does not redirect

Ella Fitzgerald
Verve//Remixed
Wait 'Till You See Him (De-Phazz remix)
83348264, 1
URL does not redirect

Nina Simone
Verve//Remixed
See-Line Woman (Masters at Work remix)
79835, 1
URL does not redirect

Billie Holiday
Verve//Remixed
Strange Fruit (Tricky remix)
1288388, 1
URL does not redirect

Sarah Vaughan
Verve//Remixed2
Whatever Lola Wants (Gotan Project remix)
2237453, 3
Matched

Ella Fitzgerald
Verve//Remixed2
Angel Eyes (Layo & Bushwacka remix)
2237453, 3
Matched

Hugh Masekela
Verve//Remixed2
Mama (Metro Area Birthday dub)
2237453, 3
Matched

Astrud Gilberto
Verve//Remixed2
Here’s That Rainy Day (Koop remix)
4183088, 1
URL does not redirect

Nina Simone
Verve//Remixed2
Black Is the Color of My True Love’s Hair (Jaffa remix)
2237453, 3
Matched

Alex1 · July 17, 2020, 5:21pm

Yes, I am very thorough

I used Shazam with this and this result.

I verified audibly against this and this version on music.youtube.com.

I checked whether the song might have been trimmed or is missing the end. It is not.

I am pretty sure it is the R.I.P Radio Edit. Hex Hector’s name is erroneously listed in the song name as others have noted.

sibilant · July 17, 2020, 7:38pm

Wow, so all these years later, that is still a problem. Supposedly, Apple Music used to overly rely on file tags for identification, whereas iTunes Match incorporated acoustic fingerprinting. Both methods sometimes returned a different version of a song. I don’t think either service uses metadata-only matching any longer, but your experience shows that it still can’t distinguish between different versions of a song.

I don’t know how much consideration iTunes Match gives to file tags, but that’s the easiest place to begin troubleshooting. If the match failed even though the original file had complete, accurate tags, here are two options:

Complain to customer service. In the past, they have given vouchers to customers so that they can buy the track.
Submit a different copy of the track, and hope that it matches properly.

Alex1 · July 17, 2020, 8:19pm

I came across 2 albums (15 tracks) this afternoon, which are not given the Album ID and Artist ID tags, after having downloaded the iTunes Plus versions. So ya, maybe I was too fast to think this can be depended on.

Alex1 · July 17, 2020, 8:42pm

I have not experienced failed matching so far - in the sense that an iTunes Plus version was clearly different from the one it replaced.

The upgrade is a free service, but still, it is a matter of accountability (of business ethics) to reveal which album was used. Image you’re the company offering this matching service. Would you hide this information from your customer? I don’t like this about iTunes Match.

It is like offering someone a bottle of wine without a label on it.

When I started with this whole review and upgrade process, I did sometimes trigger a re-match if I wanted to try my luck on songs with iCloud status “Uploaded”, following this tip by Jeff V. But it takes time, and most of the time a song got uploaded again, not matched.

sibilant · July 18, 2020, 4:04am

Yeah, the service has some problems, and lack of transparency is one of them. I’m disappointed that this didn’t turn out to be a reliable process. It doesn’t make sense to me that they would choose the wrong track and also add the wrong metadata. If they chose the track from their library, they have the track ID. It’s just bad.

I used to do that, too, and sometimes it was successful. In this case, I was suggesting using a recording from a different source, if you have one—such as a re-rip from the same CD. Try feeding them the radio edit; maybe they’ll give you the album version.

Anyway, the outcomes can be hard to predict. Sometimes it accurately matches corrupt MP3s, but is confused by high-quality recordings from official sources. Oftentimes it accepts every track but one from a perfect digital media release.

Alex1 · July 18, 2020, 12:34pm

My plan is to run a filter over my entire iTunes library in Kid3 (found under Tools > Filter…) in order to see which tracks have the Album ID field set in the MP4 tag. With 891 tracks upgraded to 256 kbps m4a files so far, I could then see which percentage of those have this tag set.

I am in the process of figuring out (issue 527), how the expression for this filter should look like - something like this:

not %2{Album ID} equals ""

I don’t know what the field name for “Album ID” is to use in the curly braces. I tried different things:
albumid
ALBUMID
@albumid
albid

etc.

Does anyone know where to look this up? A resource like this mapping table?

outsidecontext · July 18, 2020, 3:15pm

Kid3 has its own mapping table at https://docs.kde.org/trunk5/en/extragear-multimedia/kid3/commands.html#table-frame-list

But it does not list Album ID, and I actually don’t know how Apple stores this in their files. If you’d install the mutagen Python library it comes with a command line tool called mutagen-inspect which you could run on the file and it would output all tags with their technical name. With that we could figure out how it is stored. It would even make sense to add support for this to Picard (as “iTunes Album ID” or such).

Alex1 · July 18, 2020, 5:30pm

The internal name for Album ID is plID. Urs Fleisch explained how to find it in the Kid3 user interface.

With the expression not %2{plID} equals "" then applied as a filter, I have 732 tracks with an Album ID set. That indicates that this tag gets applied more often than not. @psychoadept

psychoadept · July 18, 2020, 6:34pm

I haven’t been able to find any files that didn’t come from iTunes originally that have those tags. Since I’m coming from a non-iTunes library, only using iTunes for matching, that’s not terribly surprising. Do you know for sure that it’s not just retaining the tags they already had, when you do the match?

Alex1 · July 18, 2020, 6:58pm

Yes, for sure. the Album ID and Artist ID tags were not already there before replacement with a matched file in iCloud Music Library.

To check, in Kid3 I exported the filtered track list as a playlist and imported that playlist into iTunes. Then I compared it to a playlist containing all the upgraded tracks (the 256 kbps m4a aka “iTunes Plus” files). There are only 19 of the 732 tracks that are not also in the “upgraded” playlist, and that’s because they are already in iTunes Plus format. With other words, “all” of them are in the “upgraded” playlist.

Of the 892 tracks in the upgraded playlist, 179 didn’t receive the Album ID and Artist ID tags.

This is enough proof that these tags get added by Apple when a download is requested.

That’s good – just need to see how reliably these can be used to infer the source album.

Alex1 · July 20, 2020, 4:46pm

I might have discovered something – I am going to describe what I did first, and then say what I think it means, regarding if and when Apple adds the Album ID and Artist ID tags:

I have several tracks from “When a Man Loves a Woman”. I matched them via Picard with this release. Some of the tracks have iCloud status “Matched”. Rather than downloading m4a versions to replace them with, I first created copies of the audio files and imported them into iTunes.

In Tunes, I waited for the imported set to become matched again with iCloud Music Library.

Now I had two sets of matched tracks - the original set and the imported set.

Then I replaced the imported set by downloading the m4a versions. Then I checked with Kid3 whether Album ID and Artist ID tags are present. They are not.

Then I replaced the original set by downloading the m4a versions. This time, Album ID and Artist ID tags present.

So, this is what I think this means:

I signed up for the iTunes Match service 11 months ago. This means my library was scanned 11 month ago and the “iCloud Status” information on all of the tracks is from that time.

When I replace one of the tracks that were matched 11 months ago, Album ID and Artist ID are added. When I replace any track that was matched today (or more recently), that does not happen.

That means the scheme (for lack of a better word) that Apple uses to describe the link between a customer’s local copy and a track in iCloud Music Library has changed. They are no longer writing Album ID and Artist ID into the files.

However, the information that instructs what to write into the files, does still exist. So, when I request a download today for a track that was matched some time ago, the information from some time ago is used and that’s why I get Album ID and Artist ID for this track.

I will continue to test this theory with the tracks I am going to process next.