Multi-Room Sync
The core feature of SendSpin Player is perfectly synchronized audio playback across multiple devices. Every device connected to the same server plays the same music at the same moment.
How Synchronization Works
Section titled “How Synchronization Works”Clock Synchronization
Section titled “Clock Synchronization”Each device’s clock drifts slightly relative to the server. SendSpin Player uses a Kalman filter to continuously estimate the offset between the device clock and the server clock. This provides sub-millisecond accuracy in time estimation.
Timestamped Audio
Section titled “Timestamped Audio”Every audio chunk from the server carries a precise timestamp indicating when it should be played. The player buffers incoming audio and plays each chunk at exactly the right moment.
Sample-Level Correction
Section titled “Sample-Level Correction”If the player detects that audio is slightly ahead or behind where it should be, it applies gentle correction by inserting or dropping individual audio samples. This correction stays within +/-4% of the normal playback rate, which is imperceptible to the listener.
Setting Up Multi-Room
Section titled “Setting Up Multi-Room”- Install SendSpin Player on each Android device
- Connect all devices to the same SendSpin server
- Audio plays in sync automatically
Device Names
Section titled “Device Names”Give each device a unique Player Name in Settings so you can identify them on the server (e.g., “Kitchen Tablet”, “Bedroom Speaker”).
Groups
Section titled “Groups”If your server supports groups, you can assign devices to different groups to play different audio in different rooms. Switch groups from the Now Playing screen using the group switcher.
Fine-Tuning Sync
Section titled “Fine-Tuning Sync”Manual Sync Offset
Section titled “Manual Sync Offset”If a particular device consistently sounds slightly early or late (due to audio hardware latency), adjust the Manual Sync Offset in Settings:
- Positive values — Delay playback (the device is playing too early)
- Negative values — Advance playback (the device is playing too late)
Start with small adjustments (10-20ms) and test by listening alongside another synced device.
Audio Codec
Section titled “Audio Codec”All devices in a group should ideally use the same audio codec for the most consistent sync. Choose the codec in Settings under Preferred Audio Codec.
Best Practices
Section titled “Best Practices”- Use WiFi for all synchronized devices (cellular adds unpredictable latency)
- Place devices on the same network with a local connection for best results
- Use wired audio outputs when possible (Bluetooth adds 50-200ms latency that varies by device)
- If using Bluetooth, adjust each device’s sync offset to compensate