I've been noticing a major gap when casting to a chromecast audio device. Looking into it further, it looks like gapless control must come from the player implementation (https://code.google.com/p/google-cast-s ... id=745#c21).
The suggestion by the google devloper is to utilize media source extensions (MSE) to implement gapless playback. There seems to be a nice tutorial on how to implement this below:
https://developers.google.com/web/updat ... udio?hl=en
I've been casting from my phone in offline mode since my subsonic server is down at the moment, so I think all the 'casting' must be handled by dsub.
Thank you for considering!
EDIT: fixed links