EDIT: you can try to set a column to $meta(artist,0) and see if it always display the artist.
Thanks for the suggestion. I tried it and it is returning "Unknown". I still can't find a pattern as to when it gets the artist tag successfully and when it does not. Is there any other test I can do to help?
I had some more time to look into this and here's what I found.
In the properties of a file that does not show the artist properly, I see:
<UPNPDIDL>:
<DIDL-Lite xmlns="urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:upnp="urn:schemas-upnp-org:metadata-1-0/upnp/" xmlns:dlna="urn:schemas-dlna-org:metadata-1-0/"><item id="1$12$1684301006$1684301013$3026479887" refID="1$268435466$2013266774" parentID="1$12$1684301006$1684301013" restricted="1">
<dc:title>Party Up</dc:title>
<dc:creator>Unknown</dc:creator>
<upnp:artist>DMX</upnp:artist>
<upnp:album>Unknown</upnp:album>
<upnp:genre>Unknown</upnp:genre>
<res size="6446891" duration="0:04:29.000" protocolInfo="http-get:*:audio/mpeg:DLNA.ORG_PN=MP3;DLNA.ORG_OP=01;DLNA.ORG_FLAGS=01700000000000000000000000000000">http://removedip/disk/music/DLNA-PNMP3-OP01-FLAGS01700000/O1$12$1684301006$1684301013$3026479887.mp3</res>
<upnp:class>object.item.audioItem.musicTrack</upnp:class>
</item></DIDL-Lite>
<UPNPSIZE>:
6446891
This second file does show the artist, but only when foobar actually plays the song. I don't know why it only shows the artist when it plays the song, because when I look at the file properties through foobar, the UPNP tags appear to be complete:
<UPNPDIDL>:
<DIDL-Lite xmlns="urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:upnp="urn:schemas-upnp-org:metadata-1-0/upnp/" xmlns:dlna="urn:schemas-dlna-org:metadata-1-0/"><item id="1$12$1684301006$1684301013$3026479965" refID="1$268435466$2013266813" parentID="1$12$1684301006$1684301013" restricted="1">
<dc:title>On My Block</dc:title>
<dc:creator>Unknown</dc:creator>
<upnp:artist>Scarface</upnp:artist>
<upnp:album>Unknown</upnp:album>
<upnp:genre>Blues</upnp:genre>
<dc:date>2002-01-01</dc:date>
<res size="5079839" duration="0:03:32.000" protocolInfo="http-get:*:audio/mpeg:DLNA.ORG_PN=MP3;DLNA.ORG_OP=01;DLNA.ORG_FLAGS=01700000000000000000000000000000">http://removedip/disk/music/DLNA-PNMP3-OP01-FLAGS01700000/O1$12$1684301006$1684301013$3026479965.mp3</res>
<upnp:class>object.item.audioItem.musicTrack</upnp:class>
</item></DIDL-Lite>
<UPNPSIZE>:
5079839
I am using foobar 9.6.9 and foo_upnp 0.99.12. Files are being streamed from a TwonkyMedia Server 4.4.17. Clearly the artist information does exist for both files, but for the first one, it never shows it in foobar, and in the second one, it only shows when I play the song. (As an aside, the track title always appears.)
Nobody else have this issue?