What is Simulcast?
Simulcast distributes the same live program concurrently in multiple versions, through multiple media, or to multiple services. Versions may differ in bitrate, resolution, destination, or delivery format.
How Simulcast works
A simulcast workflow fans one program out into concurrent outputs, either by encoding several renditions or relaying variants to distinct distribution systems. Timing and content remain aligned enough that each output represents the same event, although latency and presentation details can vary by path. In real-time communications, a sender may publish multiple concurrently encoded versions of the same source, differing in resolution, frame rate, or bitrate, so a receiver or forwarding server can select among them. In broadcast operations, routing, monitoring, and entitlement are managed per destination.
Key facts
- 1Encoding several renditions at the source consumes more compute and uplink bandwidth than sending one, but it can let downstream selectors switch streams without transcoding.
- 2Aligned keyframes across bitrate variants are important when a player or distribution system switches between them; poor alignment can cause delayed or visible transitions.
- 3Failures are destination-specific: successful publication to one platform does not confirm another endpoint is receiving, so health and credentials need independent monitoring.
When Simulcast matters
Use simulcast to reach several platforms or network conditions from one event. Each added rendition or destination consumes encoding or outbound capacity and introduces another endpoint whose failure must be handled.