Sendspin-audio Provider

Sendspin-audio is an audio playback, control, and synchronization protocol developed by the Open Home Foundation. It is the native playback protocol built into Music Assistant, providing synchronized audio playback across multiple clients with sample-accurate timing.

Because Sendspin is license-free and open source, anyone can build apps, devices, and integrations using the protocol. The specification is available at github.com/Sendspin/spec.

CAUTION

Technical Preview

Sendspin and its implementation in Music Assistant are currently in technical preview. While functional, the protocol and implementation may change.

Features

• Synchronized multi-room audio: Sample-accurate playback across all connected devices
• Automatic discovery: Sendspin devices on your network are automatically detected by Music Assistant
• Per-player DSP: Individual equalizer and volume settings for each device
• Bidirectional control: Clients can control playback (play, pause, skip, etc.)
• Real-time metadata: Track info, artwork, and playback progress on all devices

Configuration

The Sendspin provider is built-in and always enabled. There are no configuration options required to get started.

Individual Sendspin players will appear automatically when clients connect

Settings

Standard player settings apply. Specific settings available for this player type are:

• Sync delay (ms). Not all devices allow this correction but when available is allows a for static delay to be applied for audio synchronisation
• Output channel mode. The default is Stereo but other options are Left channel only, Right channel only or Mono (both channels)

Known Issues / Notes

• The Sendspin provider is added by default
• The web player appears automatically in the player list

Limitations

• Technical preview: The protocol is still evolving
• Network requirements: For direct connections, devices must be on the same network as Music Assistant
• WebRTC requirements: For remote access via WebRTC, Home Assistant Cloud (Nabucasa) provides optimal TURN server support for reliable connections through firewalls

Specification Compliance and Deviations

There are some gaps between this implementation and the specification at github.com/Sendspin/spec. Both are subject to change. Known deviations include:

• Player Format Changes through stream/request-format are not yet supported
• The paused playback_state is never used - only playing and stopped are sent to clients
• All streams are ended immediately when playback stops, skipping to the next track, or when seeking. Artwork is also cleared during pause, seek, or loading of the next track
• Multi Server Support messages are implemented but not fully utilized - only a single server per network is supported
• Only 16-bit audio formats are supported

Supported Clients

Several client types can connect to Music Assistant via Sendspin:

Client	Description
Web Browser	The built-in Music Assistant web player uses Sendspin for local playback
Google Cast (Sendspin mode)	Experimental Sendspin mode for Chromecast devices
Home Assistant Voice PE	Alpha firmware for the Home Assistant Voice Preview Edition
Sendspin Bluetooth Bridge	Bridges Bluetooth speakers as MA players — multi-device, multiroom sync, web dashboard. Deploys as HA addon, Docker, or LXC
Various Sendspin Clients	Clients are becoming available for various platforms

How It Works

Automatic Discovery

Sendspin devices on the local network are automatically discovered via mDNS and will appear in Music Assistant. No manual configuration is required.

The Web Player

The built-in web player in the Music Assistant frontend uses Sendspin for audio playback. When on a local network, the web player will attempt to use a direct WebSocket connection for best performance; otherwise it falls back to WebRTC.

The sync delay can be adjusted under Settings → User Interface → Sendspin sync delay. This value is auto-selected based on the platform but may need manual adjustment.

Codec Support

The audio codec used depends on the connection and platform:

• Local connections (on the same network): FLAC (lossless) is used on desktop browsers and Android. iOS, iPadOS, and Safari use Opus.
• Remote connections (via WebRTC): All browsers use Opus.

NOTE

Firefox on Android does not support remote (WebRTC) playback.

Connection Methods

Sendspin supports two connection methods:

1. Direct WebSocket: Used automatically by clients on the same local network as Music Assistant, including the web player and hardware devices.
2. WebRTC: Used for remote access when not on the local network. Works across networks and through firewalls. The web player falls back to this method when a direct connection isn’t possible.