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Tag separation deliminators
#4
<tl;dr> 

It's complicated.

<long answer>

There are several issues involved here.

1) Different metadata schemes deal with multiple values differently. 

The spec for ID3v2.3 (widely used to tag MP3) says nothing about it. Since it allows only one instance of each type of text information frame (such as genre), various people try private markup using some in-band field separator (besides the semi-colon, I've seen a double reverse solidus "\\" used, for example). Trouble is, many applications have no idea those private solutions mean something special.

The Vorbis Comment scheme (used to tag FLAC) uses unstructured key/value-pairs, one value per pair, and allows multiple occurrences of a key (such as genre). Like Vorbis Comments, APE2 (can be used to tag MP3) uses key/value-pairs but allows for a list of values for a given key. I don't know what the Apple iTunes and Windows Media schemes say about multiple values.

2) The MPD tag-reader plugins have to know what to do with the multiple values. The MPD docs says it allows for multiple occurrences: "There can be multiple values for some of these tags. For example, MPD may return multiple lines with a performer tag." However, this has to be tested for each format and metadata scheme. For sure, in-band separators such as semi-colon and reverse solidus mean nothing to it.

A long time ago I was testing MPD's plugins specifically to see how they map Vorbis Comments into MPD's list of "supported tags" but I didn't look specifically into multiple values. I need to refresh and extend my directory of hand-crafted test files to include MP3, AAC, ALAC, WMA formats and other metadata schemes and see where the plugins stand today.

3) Then moOde has to do something sensible with multiple lines returned by MPD. In the case of genre this can be a sticky point because different people have different wants. With classical music, for example, many people have an somewhat hierarchical classification scheme in mind. Try getting them to agree a specific scheme!

Regards,
Kent
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Messages In This Thread
Tag separation deliminators - by Bedlore - 11-01-2019, 09:45 AM
RE: Tag separation deliminators - by Bedlore - 11-04-2019, 08:21 AM
RE: Tag separation deliminators - by Tim Curtis - 11-04-2019, 11:35 AM
RE: Tag separation deliminators - by TheOldPresbyope - 11-04-2019, 02:33 PM

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