Two jobs: contribution and delivery
Contribution, also called ingest, is the first mile: one stream from an encoder to the platform. It needs low delay and resilience on a single connection. Delivery is the last mile: the same stream to thousands or millions of viewers. It needs to scale through CDNs and adapt to each viewer's connection.
Contribution protocols
- RTMP: the long-standing default, supported by every encoder
- SRT: resilient over unreliable networks, with built-in encryption
- RIST: a standardized alternative to SRT, used in broadcast
- WebRTC (WHIP): very low delay ingest from browsers and newer encoders
Delivery protocols
- HLS: segment-based, works everywhere, required for Apple devices
- MPEG-DASH: segment-based open standard, common on Android and smart TVs
- Low-Latency HLS and low-latency DASH: the same protocols tuned for a delay of a few seconds
- WebRTC: sub-second delivery for interactive uses, harder and costlier to scale
How to think about the choice
On a managed platform the delivery protocol is chosen for you per device, and the only decision is how your encoder sends the feed. Where a choice exists, it is a balance of three things: delay, reach across devices, and cost at scale. Segment-based delivery over HTTP wins on reach and cost, which is why it carries nearly all streaming video; real-time protocols win on delay.
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