Roku SoundBridge devices can be treated as dumb speakers; they offer a
texted based protocol, RCP, that allows the server to request the Roku
device to connect to the server's stream.mp3 and provides ability to
control volume
Roku devices appear as speakers automatically via mDNS announcements on
the server _roku-rcp._tcp
Select use of either libspotify or librespot-c as streaming backend via config
option.
librespot-c (renamed/improved spotifyc) impl has the following:
- sync interface
- seek support
- honor bitrate config, set client and thread name
- use web access token with "streaming" scope for login
- fix issue with podcast playback
Also say goodbye to file-based Spotify login.
