Sonos has a remarkably good implementation of all of this.
For URL-based streams they buffer and NTP to sync. For live streams (e.g. gaming) they p2p multicast and tweak the wifi params in real-time to minimize drops.
The speakers create their own wifi and use MST network heuristics to latency-min route over that versus native wifi or ethernet if you've plugged it in. Sound drops when the wifi spectrum blinks (rarely), but I have never encountered the speakers being out of sync or noticing an echo effect.
And the speakers can use your phone's mic to scan the soundscape of a room to acoustically balance the sound when you set them up. I particularly like how consistent the sound volume is room-to-room even with very different speaker setups.
IIRC they've patented their specific mechanism. So ya, it's solved, but it may be expensive to license.
(Not affiliated with Sonos, I just have a bunch of them and like them a lot.)
Yeah, Sonos is very much the Apple of this space. A solid, user-friendly implementation of several pre-existing concepts into a cohesive product - no small task. I don't think the technologically important parts of this are patentable though, there's both prior art and the obviousness standard to worry about. But very much like Apple's 'rounded corners' case, they've gone after (IMO) obvious UI functionality for such a system to extract money from their competitors.
If you are just interested in the synchronized Audio-over-Ethernet part, AES67 is the industry standard, and a pretty complete open-source implementation can be found at https://github.com/bondagit/aes67-linux-daemon , though AES67 is itself a composition of existing standards, fundamentally it is mostly composed of SDP for sessions description, RTP for media, and PTP for clock sync, so you can build that out of a variety of implementations too.
The patent actually covers a mechanism for electing a master controller for synching and storing configuration parameters. The actual process of synching audio is not covered. Not that difficult to work around the patent. But definitely easy to trip over the patent if you're not careful.
For URL-based streams they buffer and NTP to sync. For live streams (e.g. gaming) they p2p multicast and tweak the wifi params in real-time to minimize drops.
The speakers create their own wifi and use MST network heuristics to latency-min route over that versus native wifi or ethernet if you've plugged it in. Sound drops when the wifi spectrum blinks (rarely), but I have never encountered the speakers being out of sync or noticing an echo effect.
And the speakers can use your phone's mic to scan the soundscape of a room to acoustically balance the sound when you set them up. I particularly like how consistent the sound volume is room-to-room even with very different speaker setups.
IIRC they've patented their specific mechanism. So ya, it's solved, but it may be expensive to license.
(Not affiliated with Sonos, I just have a bunch of them and like them a lot.)