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The Open Home Foundation’s Sendspin multi-room audio protocol has reached Release Candidate 1 as its first official specification and SDK are being finalized. Music Assistant can use bridges to group some existing speakers with native Sendspin devices, but compatibility varies and a final 1.0 release has not been announced.
Sendspin, the Open Home Foundation’s open protocol for synchronized multi-room audio, has reached Release Candidate 1 as its first official specification and software development kit are being finalized. The development gives Music Assistant and ESPHome a shared approach to coordinating audio across native Sendspin devices and some bridged speakers, including compatible AirPlay and Google Cast hardware, though support depends on the device and its software.
Sendspin is designed to coordinate playback across devices that do not normally belong to the same audio ecosystem. In the account by Matter Alpha, Music Assistant 2.8 is described as using Sendspin Bridges to present certain compatible devices as Sendspin players. The underlying speaker can continue using its existing transport while Sendspin coordinates group timing. This can let users test mixed systems without first replacing every speaker, but it does not make every AirPlay, Sonos or Cast product compatible.
The protocol’s specification covers more than synchronized audio. It defines roles for players, audio sources and controllers, as well as metadata, artwork, visualizers and color information. A server can coordinate playback while other devices show album art, provide controls or use visualization data for lighting. Sendspin devices can also send captured audio, such as sound from a turntable or CD player, back to a server for distribution around a home.
According to the report, the current specification requires servers to support PCM and FLAC, while Opus is optional. Clients can advertise codec and audio-format preferences, including channel count, sample rate and bit depth. Connections are local and use end-to-end encryption based on the Noise Protocol Framework. The project has also had a significant qualification: the Open Home Foundation team says Cast Audio bridging support in Music Assistant will be removed after Google decided to slim down its firmware. Cast devices with displays are still expected to work for playback information, according to the report.
A Bridge Across Speaker Ecosystems
Multi-room audio works well within many individual platforms, but coordinating different brands and device types can be difficult. Sendspin’s practical promise is to provide a shared timing and control layer, rather than require all speakers to use the same manufacturer’s system. If the approach gains wider support, households could have more flexibility to combine existing commercial speakers with open-source or do-it-yourself hardware.
The bridge model also matters for people who already own speakers. It may lower the cost and disruption of trying an open system, because compatible devices can participate through their current playback methods. That benefit is conditional: the report notes that hardware and firmware limits can prevent some devices from working, and the announced change to Cast Audio bridging shows that upstream platform decisions can alter what a bridge supports.
Sendspin’s broader roles could let developers build listening experiences that connect audio with displays, controls and lighting. That is a potential use, not evidence that all such integrations are available across products today. The significance will depend on the quality of implementations and how many device makers and software projects adopt the protocol.
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From Open Home Project to Release Candidate
Sendspin was developed by the Open Home Foundation, the nonprofit behind projects including Home Assistant, ESPHome and Matter.JS. Matter Alpha reports that the foundation’s portfolio includes more than 250 open-source projects, standards, drivers and libraries. Foundation president Paulus Schoutsen told the outlet that the team looked to existing technology where it already solved a problem, but saw a gap around experimentation across established audio ecosystems.
The report traces the idea to discussions among team members at a Connectivity Standards Alliance meeting in Chicago, where they considered multi-room audio and alternatives such as Snapcast. The project then took shape through more than a year of work by several full-time contributors. Sendspin is now at Release Candidate 1; the report says its initial formal specification and SDK are being finalized, but gives no date for the completed 1.0 release.
Music Assistant is described as providing server-side support and using Sendspin for native synchronized playback. ESPHome offers a path for new hardware to join directly, while Music Assistant bridges can bring some existing devices into a Sendspin group. These are distinct routes: native support depends on device implementation, while bridging depends on the capabilities and continuing support of the original device platform.
“If you want to play with this, if you want to experiment with this, if you want to make your own program that receives this multi-room audio and maybe visualize it, offer controls, or play it in a way that is not envisioned by the creators or the gatekeepers of Cast and AirPlay or Sonos, you couldn’t do it.”
— Paulus Schoutsen, Open Home Foundation president, speaking to Matter Alpha
Compatibility Depends on Devices
Release Candidate 1 is not the final 1.0 release, and the source report does not provide a completion date or a final adoption plan. It also does not establish how many speakers will support Sendspin natively, which manufacturers may add it, or how broad compatibility will be across existing AirPlay, Sonos and Cast products.
Bridging does not guarantee that a device can join a group. The report flags hardware and firmware constraints, and says Music Assistant’s Cast Audio bridge support is due to be removed after Google’s firmware changes. The exact devices affected and the timing of that removal are not specified in the supplied material. Cast devices with displays are described as retaining playback-information support, but that is not the same as continued Cast Audio bridging.
The report describes local connections and Noise-based end-to-end encryption, but does not provide independent testing details or explain how every implementation will handle security updates and interoperability. Those questions, along with real-world synchronization performance in mixed systems, remain open as the specification and software mature.
Final Specification and Device Support
The next milestone is completion of Sendspin’s official specification and SDK, followed by a final 1.0 release; no release date is given in the source. Developers and users can watch for updates from the Open Home Foundation, Music Assistant and ESPHome, including details of supported roles, device requirements and changes to bridging.
For people considering a mixed-speaker setup, the practical next step is to check the current compatibility information for each exact device and software version rather than assume that a product’s AirPlay, Sonos or Cast branding guarantees Sendspin participation. Further adoption by hardware makers and software projects will determine whether the protocol becomes a durable common layer or remains concentrated among early implementations.
Key Questions
What is Sendspin?
Sendspin is an Open Home Foundation protocol for coordinating multi-room audio and related information, including playback controls, metadata and visualizer data. Its goal is to support synchronized experiences across compatible devices and software.
Has Sendspin 1.0 been released?
No. The protocol has reached Release Candidate 1, while the first official specification and SDK are being finalized. The source report does not give a date for the final 1.0 release.
Can Sendspin combine AirPlay, Sonos and Cast speakers?
Music Assistant can bridge some compatible devices into Sendspin groups, according to the report, but support is not universal. It depends on device hardware, firmware and software support; Cast Audio bridging is also set to be removed from Music Assistant after a Google firmware decision.
Do users need to replace their existing speakers?
Not necessarily. A compatible speaker may join through a Music Assistant bridge while continuing to use its existing audio transport. Other devices may need native Sendspin support, and some products may not be compatible at all.
Source: rss
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