ffprobe does not recognise MusicBrainz tags in .m4a files

[smoothquark 5]

Hi. I am not sure if this is the correct sub-forum to ask. I have some .m4a files which I have tagged with MusicBrainz tags using Picard. I have different releases of the same album (16/44.1 FLAC, 24/96 FLAC, .m4a) with different Release IDs. The .flac files get listed correctly as separate albums but .m4a files get lumped together with one of the other .flac albums, so there are duplicated tracks in that album. I think this is because ffprobe cannot read the MusicBrainz tags in .m4a files. MediaInfo does pick up the tags and in AtomicParsley tags are listed as Atom "----" [com.apple.iTunes;MusicBrainz Album Id] etc., as I presume the iTunes tagging does not directly support custom tags.

So, I don't think there is any way to get around the ffprobe limitation. Can the metadata be edited for Emby via a script using the API? Editing the metadata manually is an option but will quickly get extremely tedious! Alternatively, should I be using something other than Picard for .m4a files?

Example from Madonna's Immaculate Collection (atmos mix) Track 01: Holiday

ffprobe:

Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: mp42dby1
    title           : Holiday
    artist          : Madonna
    album           : The Immaculate Collection
    track           : 1/17
    disc            : 1/1
    album_artist    : Madonna
    sort_album_artist: Madonna
    sort_artist     : Madonna
    creation_time   : 2023-05-02T06:48:53.000000Z

mediainfo:

MusicBrainz Album Release Country        : US
MusicBrainz Album Status                 : official
MusicBrainz Album Type                   : album / compilation
MusicBrainz Release Track Id             : 166b449f-072b-4c7c-adc6-47dda677f90c
MusicBrainz Work Id                      : 1c03c879-e386-38e1-b823-386d3ef9e27f
MusicBrainz Track Id                     : 3a0be7df-1b08-40ad-816f-b8e3c3e17aea
MusicBrainz Album Id                     : 403b2773-5f4e-4aa5-a5c3-0f4f832fab2b
MusicBrainz Album Artist Id              : 79239441-bfd5-4981-a70c-55c3f15c1287
MusicBrainz Artist Id                    : 79239441-bfd5-4981-a70c-55c3f15c1287
MusicBrainz Release Group Id             : b14e9927-081e-4a07-b0f7-8ddf22319b27
 

Thank you.

[smoothquark 5]

Update: I am making some progress with the API now to update metadata. Not completed, yet, though.

[smoothquark 5]

I have now updated the MusicBrainz tags on the .m4a files and they show up in the Metadata Editor. However, the tracks from the .flac and .m4a albums are lumped as one album although they have different MusicBrainz Albums IDs. Scanning files and refreshing metadata does not change this. 

[smoothquark 5]

Finally made some progress. I needed to use AtomicParsley to "correct" the metadata as written by Picard. However, rescanning the library and also updating the metadata did not help. I had to delete the whole library and add it in again. So, looks like there is still a bug in Emby where updating metadata, and rescanning, whilst it does seem to do something according to the logs anyway, does not actually update the database.

[Luke 42080]

Hi, thanks for following up. What information didn’t update for you after you ran the library scan?

[smoothquark 5]

Thanks Luke. Pity... I should've taken some screenshots. Anyway as a summary using my Madonna Immaculate Collection as an example...

1. 2 versions - (16/44.1) 2 channel FLAC and (24/48) Atmos .m4a (different MB ids but MB ids initially not picked up by ffprobe) 

2. Both imported as one album with and tracks lumped together.

3. Entered the MB ids for the .m4a tracks using the metadata editor. This did not move the tracks to a separate album.

4. Ran update metadata (all) and rescanned library - still did not move tracks to a separate album.

5. I then discovered that I need to use AtomicParsley on the .m4a files to "correct" the MB metadata saved by Picard. This was on some test files and not the actual files in the library.

6. Removed the MB metadata that I had previously manually added through the metadata editor (No. 3)

7. Ran update metadata (all) and rescanned library - MB metadata was now picked up but the tracks remained lumped together as one album as before.

8. Deleted the library completely and then re-added the folders and rescanned - this time the tracks were imported correctly as 2 separate albums.

As an addendum, I have noticed multiple times where rescanning tracks with updated metadata does not always replace the older metadata but no errors show up in the logs. Not always though - sometimes it works fine! Also, I have some orphaned Artists from some removed albums. They do not show up on the web interface but appear when I run the API. I picked this up as I am currently writing a script to looks for inconsistencies in my music library. One of those inconsistencies is when the album_artist tag has multiple artists separated by a ',' - they get put down as one artist although the first artist is correctly identified in the descriptions. MB tags are correctly picked up and separated by '/' within the metadata editor. I ought to start a separate topic, I think.

[Luke 42080]

Quote

One of those inconsistencies is when the album_artist tag has multiple artists separated by a ',' - they get put down as one artist

@smoothquarkHi there, can you please provide a specific example? Thanks.

[Vicpa 611]

Hi 

there is a known limitation with support for multiple value tags in the m4a container.  @softworkzcan provide details. 

Not a bug but more of an "Apple standard" as I understand it. 

On 6/12/2024 at 5:09 PM, smoothquark said:

However, rescanning the library and also updating the metadata did not help. I had to delete the whole library and add it in again. So, looks like there is still a bug in Emby where updating metadata, and rescanning, whilst it does seem to do something according to the logs anyway, does not actually update the database.

The above observation has been noted as well before . It is unclear what changes to the underlying data emby actually captures.

[smoothquark 5]

12 hours ago, Luke said:

@smoothquarkHi there, can you please provide a specific example? Thanks.

I managed to solve this. I thought I had posted my findings, but perhaps I forgot to. Anyway,  it looks like the albumartists tag is required. Kodi has the same issue.

My notes:

https://kodi.wiki/view/Music_tagging#albumartists
Kodi/Emby need the albumartists tag to index multiple album artists correctly.
Picard: a new script under Options > Options > Scripting > Add new script
and include the following code..
$setmulti(albumartists,%_albumartists%)
 

Interestingly, as the MusicBrainz tags are imported correctly (even .m4a files when AtomicParsley is used to resave tags), Emby ought to set the correct artists based on the MusicBrainz tags. 

[Luke 42080]

Hi, this is correct. The server uses the mbz id's to fetch metadata for the artists/albumartists that are already set...not to create them in the first place.

[softworkz 5068]

16 hours ago, Vicpa said:

there is a known limitation with support for multiple value tags in the m4a container.  @softworkzcan provide details. 

I don't remember much about it (too much information flowing through this brain), so the best information available is in what I have written about it at that time.