Wishlist: Library sharing via DAAP

[fwcd]

Feature Description

It would be nice to have support for DAAP, a protocol introduced by iTunes/Music and implemented in a number of open source clients (Rhythmbox, Banshee) and servers (ownTone, Ampache). Mixxx could benefit from this both as a server (to share the current library) and client (to discover and access other libraries over the network, both from Mixxx and other DAAP servers).

On the technical side, DAAP seems to be largely HTTP with a custom tagged binary format and mDNS/DNS-SD (aka. Avahi/Bonjour) for service discovery on the local network, so likely not super hard to implement.

Side note: There are a number of similar protocols, e.g. including UPnP- and mDNS-based ones (e.g. MPD). This issue focuses on DAAP, due to its adoption in existing media players (interoperability) and relative simplicity. Since this doesn't propose to change anything about Mixxx's own library database, adding other protocols in the future should be easy (laying the mDNS groundwork will probably also simplify the implementation of other protocols)

See also:

• https://github.com/bjoernricks/daap-protocol (protocol documentation)
• https://gitlab.gnome.org/GNOME/libdmapsharing (GNOME implementation of DAAP, probably not ideal to depend on due to dependencies like glib)
• https://github.com/jbagg/QtZeroConf (potentially useful as a cross-platform mDNS/DNS-SD wrapper)
  • This could also be useful if we want to implement library discovery for other protocols in the future (e.g. MPD)
  • Worth noting that Qt may eventually upstream something similar: https://bugreports.qt.io/browse/QTBUG-30823