Synchronised digital signage enables multiple environments to function as a single cohesive display surface or to show coordinated content across distributed locations. The technology addresses a fundamental challenge: getting separate computers to play content at exactly the same moment.
**The Synchronisation Challenge**
Every display in an experience network is driven by its own media player—a separate computer with its own processor, clock, and timing characteristics. Left unsynchronised, these players drift apart over time. An video wall might start with aligned content but develop visible tears and jumps as players fall out of sync. Even small timing differences (measured in milliseconds) create visible artifacts where content spans multiple environments.
**Time Reference Synchronisation**
The foundation of synchronised playback is a shared time reference. All players in a synchronised group must agree on what time it is with extreme precision. Common approaches include:
- **Network Time Protocol (NTP)**: Synchronises clocks to internet time servers with millisecond accuracy. Sufficient for many commercial applications. - **Precision Time Protocol (PTP/IEEE 1588)**: Achieves microsecond accuracy over local networks. Used in broadcast and critical infrastructure. - **Hardware Genlock**: Physical signal that synchronises video frame output timing. Most precise but requires specialized hardware.
**Playback Coordination**
With synchronised time references, players coordinate their playback through several mechanisms:
1. **Pre-buffering**: Content is fully loaded into memory before the scheduled start time, eliminating download delays during playback.
2. **Synchronised Start Commands**: All players receive playback start commands that specify an exact future time to begin. Players wait until their synchronised clocks reach the target time before starting.
3. **Continuous Correction**: During playback, players continuously compare their position in the content against where they should be based on the time reference. Small adjustments (frame drops or repeats) keep players aligned.
4. **Heartbeat Monitoring**: Regular status updates between players and the management system detect sync issues before they become visible.
**SPARC's Approach**
SPARC uses a software-based synchronisation engine that achieves frame-accurate results without requiring expensive hardware genlock systems. All players in a sync group connect via WebSocket and receive coordinated playback commands with precise timestamps. By combining multiple timing sources with intelligent drift prediction, SPARC maintains sync across both local video walls and geographically distributed installations.