Thanks, Matt.
The iPod doesn't let you configure them on the device. These are new track properties introduced when Apple added podcast support. They let any file type use the 'bookmark' feature on the iPod and keep them from being played when using shuffle music mode. These flags are set automatically by iTunes for podcasts downloaded with iTunes. They can also be set manually on any track in the track properties or programmatically using the iTunes SDK.
It's one of those small changes that greatly improves the user experience if you listen to longer podcasts or audio books on MP3. I dislike iTunes, but I'm using it for this feature.
These iTunesDB fields are documented in the
iPod Linux wiki.
Here's an excerpt:
iTunesDB Track item:
Offset: 165 Name:Flag2 Size: 1
Desc: sets "Skip When Shuffling" when set to 0x1 (added in dbversion 0xd)
Offset: 166 Name:Flag3 Size: 1
Desc: sets "Remember Playback Position" when set to 0x1 (added in dbversion 0xd).
Note that Protected AAC files (.m4b extension) and Audible files (.aa extension) DO NOT SET flags 2 or 3, and yet are always bookmarkable and are not included in the song shuffle. To determine if a file is bookmarkable, therefore, check the file type first. If it's not an .m4b or .aa, then check flag 3 in this field in iTunesDB.
Offest:167 Name: flag4 Size: 1
Desc: some kind of "Podcast" flag (added in dbversion 0xd)? When this flag is set to 0x1 then the "Now playing" page will not show the artist name, but only title and album. When additionally flag1 is 0x2 then there will be a new sub-page on the "Now playing" page with information about the podcast/song.