Muliple FLAC vorbis comments with the same field name?

[d2b]

I know that FLAC supports multiple vorbis comments with the same field name but with different values. For example, a file might contain these comments:

COMPOSER=Gillian Welch
COMPOSER=David Rawlings

as opposed to a single comment like:

COMPOSER=Gillian Welch and David Rawlings

We've noticed that AMG (and perhaps other databases) often return metadata like this:

Composer: Gillian Welch; David Rawlings

I don't see the advantage or reason for wanting to separate co-writers or a performing duet into separate tags. In fact, it seems inappropriate, as it might cause one of the two (or more, if there are more than two) songwriters or artists to either be overlooked in a search of a database or in a display on a media player (iPod) or GUI (iTunes) assuming for this example that the FLAC files were converted to MP3.

Where did this practice of splitting values into separate comment fields originate, and why? It certain should not make it any easier for search engine purposes.

We'd rather not do it, and we'd rather be able to combine this information when CD Ripper ingests it as values separated by a semicolon.

Comment, answers or suggestions welcome....especially the answers.

Thanks in advance.

"d2b"

[Spoon]

Re: Muliple FLAC vorbis comments with the same field name?

>Where did this practice of splitting values into separate comment fields originate, and why?

It is mandated as the Vorbis Tagging Standard, if dBpoweramp were writing the same tags to mp3 it would write as Gillian Welch/David Rawlings which is correct for mp3. We follow tagging standards.

[d2b]

Re: Muliple FLAC vorbis comments with the same field name?

Multiple vorbis comments are NOT mandated by the standard for Vorbis comments as defined in xiph.org documentation. They are permissible and encouraged. But why? That was the question.

It still seems like a way to generate errors of omission by separating the names of performers or composers that worked together on a piece, instead placing them into multiple FLAC tags, each with the same field name.

For example, searching for songs tagged with a specific songwriter's name to find out which songs she's written might lead one to believe she wrote all of the songs located in the search, when in fact she may have been a co-writer on most of them. The co-writer's names would not appear in the search results.

[d2b]

Re: Muliple FLAC vorbis comments with the same field name?

I should also point out that ID3v2.3 supports multiple values in a limited number of tag types, as you point out, by separating them with a "/" character. This is not the same as generating multiple tags with the same field name. It is still one tag.

The 'equivalent' vorbis comment would be COMPOSER=Gillian Welch/David Rawlings, not two separate ones each with a single name.

If I'm not mistaken, dbpoweramp CD Ripper generates an individual vorbis comment for each artist or composer if their names are separated by a semicolon. This action makes me very uncomfortable, as it is creating multiple FLAC tags, presumably from a source such as AMG which may be delivering the metadata as a single ID3v2.3 tag with multiple values.

This kind of confusion about how metadata is handled by the various on-line suppliers and by dbpoweramp CD Ripper and Media Converter is why I've been pursuing this question in another thread on this forum.

[Spoon]

Re: Muliple FLAC vorbis comments with the same field name?

Multiple vorbis comments are NOT mandated by the standard for Vorbis comments as defined in xiph.org documentation. They are permissible and encouraged. But why? That was the question.

They are mandated in that if you have multiple artists and you want to store vorbis comments correctly then it is stored as separate. The standard does not say you can store as Artist1, Artist2 or even Artist1; Artist2 it is very specific. Your question why should be directed at the applications which cannot read the multiple tags, it is a simple specification, they have chosen not to follow the standard...

[DazBYorks]

Re: Muliple FLAC vorbis comments with the same field name?

It makes sense to separate the names, especially when you add sort strings into the equation;

COMPOSER=Gillian Welch
COMPOSER=David Rawlings

COMPOSERSORT=Welch, Gillian
COMPOSER=Rawlings, David

Daz

[d2b]

Re: Muliple FLAC vorbis comments with the same field name?

I would appreciate a pointer or URL to the site that contains the documentation that Spoon refers to. I cannot find any reference in the standard for Vorbis comments that prohibits multiple artists under one field name nor mandates a separate tag for each.

I fear that I might be missing something. However, the document that I am looking at can be found here. Note that it is dated February, 2010.

http://xiph.org/vorbis/doc/Vorbis_I_spec.html*blooper*x1-850005.2.2

It puts no constraints that I can find on how multiple artists or composers are handled.

"d2b"

[DazBYorks]

Re: Muliple FLAC vorbis comments with the same field name?

In the same document:

Field names are not required to be unique (occur once) within a comment header. As an example, assume a track was recorded by three well know artists; the following is permissible, and encouraged:

1 ARTIST=Dizzy Gillespie
2 ARTIST=Sonny Rollins
3 ARTIST=Sonny Stitt

Daz

[d2b]

Re: Muliple FLAC vorbis comments with the same field name?

Yes, I know that is says permissible and encouraged. I have already mentioned this. That is not the same as "mandatory" nor does it answer the original question.

Why are multiple comments encouraged? It seems that it could be risky to separate artists, composers or the like into separate tags instead of combining them in one.

In my original example, if I did a search on songs written by Gillian Welch (COMPOSER=Gillian Welch) , it is not obvious to me that her co-writers on some of the hits would be noted in the results, giving the impression that Gillian wrote some of the songs alone. This possibility indicates to me that multiple vorbis comments with the same field name could be potentially troublesome.

So, once again, what advantages do multiple comments with the same field name offer? Why does the Vorbis Cmment specification encourage this?

TIA...

[d2b]

Re: Muliple FLAC vorbis comments with the same field name?

I forgot to mention that I do not know the use of effect of the COMPOSERSORT comment and other "SORT" fields.

Where is these defined?

[Spoon]

Re: Muliple FLAC vorbis comments with the same field name?

They are only separated within the file, it is up to a program which reads the tags to combine them internally, like Asset UPnP does - it works perfectly.

The 'Sort' fields are non standard, you can ignore them outside of dBpoweramp and its related programs (Asset UPnP, etc).

[d2b]

Re: Muliple FLAC vorbis comments with the same field name?

In other words, a search engine looking for song titles where Gillian Welch is a songwriter (Find TITLE=X if COMPOSER=Gillian Welch) should yield this result

TITLE=X
COMPOSER=Gillian Welch; David Rawlings

for a specific song named "X" if the tags are

COMPOSER=Gillian Welch
COMPOSER=David Rawlings

Is this what you mean?

TIA...

d2b

[Spoon]

Re: Muliple FLAC vorbis comments with the same field name?

Correct

[Jassel]

Re: Muliple FLAC vorbis comments with the same field name?

Multiple vorbis comments are NOT mandated by the standard for Vorbis comments as defined in xiph.org documentation. They are permissible and encouraged. But why? That was the question.

Because in most situations it gives the most convenient results.

1) If I'm browsing composers (or artists or whatever) I like to have one entry for Dizzy Gillespie rather than 100 different for all the co-writers, projects and collaborations.
2) Furthermore, who takes precedence if several composers (or artists or whatever) have to be crammed into one tag? Sort them alphabetically? By contribution? Age? Fame? Who decides?
3) As DazBYorks pointed out: xxxSORT tags make more sense with multiple vorbis comments.

[Edu Camargo]

Re: Muliple FLAC vorbis comments with the same field name?

Foobar2000 (Windows) and Quodlibet (Linux) are two of the best examples on how these encouraged standards can be DB-friendly, when making a search. Even ID3 went to follow the Xiph's guideline when releasing the version 2.4 of their metadata format for MP3 files, despite the fact that not all players support the ID3V2.4. (Well, not every device for example supports 2.3 as well). On iTunes for example, nothing is more irritating than when you browse by a particular area, for example composer, and then you find a list like this: 'Paul McCartney/John Lennon', 'Paul McCartney/John Lennon/George Harrison/Richard Starkey', 'George Harrison/Richard Starkey', etc.

Even WMA/ASF taggs use this approach when applying multiple colaborations, although alternatively you can use a ; as a delimiter. But when you use WMP to encode music (from CD) for example, you can check with an advanced program like 'MP3Tag' that the values are wrapped this way on Windows Media Files.

Apple Atoms (used in MP4/AAC and Apple Lossless) seems to be the only format uncapable of handling information this way.