Streaming Protocols (NDI, SRT, RTMP, WebRTC, HLS)

NDI 6, SRT, RTMP, RIST, WHIP / WHEP, HLS, LL-HLS, DASH — what to use for ingest, contribution, and delivery.

The transport-layer reference for live video. For software pushing into these protocols see Live Streaming Software. For self-hosted servers terminating them see Self-host Streaming Servers. For codecs riding on top see Encoding & Codecs. For browser playback see Media Players. For SFU / meeting WebRTC see Real-time Video.

RTMP — the legacy default for ingest

RTMP / RTMPS — Adobe's TCP protocol from the Flash era; still the universal ingest format for Twitch, YouTube, Facebook, Kick, Owncast in 2026. Encoder pushes RTMP, server transcodes to HLS for delivery.
Pros: every platform accepts it; every encoder speaks it; battle-tested.
Cons: TCP-only (head-of-line blocking on flaky networks); H.264 only practically; ~2–5 s latency.
Use it for: contribution to Twitch / YouTube. Don't pick it for new self-host designs in 2026.

★ SRT (Secure Reliable Transport) — open OSS protocol from Haivision; UDP-based with ARQ retransmit; AES-128/256 encryption; the de-facto modern replacement for RTMP for contribution over public internet. Sub-second possible with tuning; ~500 ms typical.
Caller / Listener / Rendezvous modes — caller is most common (encoder dials the server).
Supported by: OBS Studio, vMix, Wirecast, Larix, MediaMTX, AntMedia, SRS, OvenMediaEngine, ffmpeg (-f mpegts srt://...).
Use it for: remote camera ↔ studio, IRL streaming, redundant uplinks. Default contribution protocol when both sides support it.

RIST (Reliable Internet Stream Transport) — VSF-standardized OSS broadcast contribution protocol; UDP + ARQ; alternative to SRT with a slightly different optimization story. Hardware encoder support strong; software support thinner than SRT.

★ NDI (Network Device Interface, NewTek/Vizrt) — proprietary but free SDK; the studio video-over-IP standard. Multiple cameras + graphics + multi-PC OBS rigs all on one Gigabit LAN at sub-frame latency. NDI 6 (2024) added multicast, AV1, HDR, improved discovery.
NDI HX — H.264/HEVC variant for over-internet / mobile / Wi-Fi; lower bitrate; iPhone NDI HX Camera uses this.
NDI 6 Bridge — tunnel NDI across sites / firewalls.
Free NDI Tools (Mac/Win): NDI Virtual Input (see Virtual Cameras), NDI Scan Converter (screen → NDI), NDI Test Patterns, NDI Studio Monitor, NDI Access Manager.
Distroav (OBS NDI plugin) — free; OBS NDI in/out (continuation of obs-ndi after the 2023 license shuffle).
vMix, Wirecast, mimoLive, Resolve all natively speak NDI.
Use it for: any LAN with more than one source machine. Free, plug-and-play, the cheapest way to "be a TV studio."

★ WHIP (WebRTC-HTTP Ingestion Protocol, RFC 9725, 2024) — sign WebRTC SDP exchanges over a single HTTPS POST; turns WebRTC into a stateless ingest protocol. Sub-second contribution.
★ WHEP (WebRTC-HTTP Egress Protocol) — playback counterpart; pull a WebRTC session via an HTTPS GET-style handshake.
OBS Studio 30+ — first-class WHIP output. vMix, Larix Broadcaster, ffmpeg (libwhip), gstreamer all speak it now.
WHIP servers: MediaMTX, AntMedia, OvenMediaEngine, Cloudflare Stream Live, LiveKit Ingress.
Use it for: any new sub-second contribution where both sides are modern. The future of RTMP.

HLS (HTTP Live Streaming, Apple) — segment a live stream into 2–10 s .ts / .m4s chunks served as .m3u8 playlists over plain HTTPS. Massive CDN compatibility.
Latency: 10–30 s standard; 6 s achievable with tight tuning.
★ LL-HLS / LLHLS (Apple) — partial-segment delivery; 2–6 s glass-to-glass; supported by HLS.js, OvenPlayer, Shaka, Apple AVPlayer.
Use it for: delivery to phones / browsers / TVs at scale.

MPEG-DASH — ISO/IEC standard; the "HLS but ISO" alternative; used by YouTube, Netflix.
CMAF — common media format unifying HLS + DASH packaging.
Use it for: when your platform mandates DASH (Android-heavy, certain DRM workflows). Default to HLS otherwise.

WebRTC — sub-second; default for video calls. As a delivery protocol, scales via SFU (LiveKit, AntMedia, OvenMediaEngine, Janus); see Real-time Video.
Use it for: live auction, live betting, watch-along, sub-second interactivity. Cost / scale model is different from HLS.

RTSP + RTP/UDP — the IP-camera protocol. Low-latency push/pull from CCTV / IP cams. MediaMTX is the universal RTSP swiss-army knife.
Use it for: NVR / camera bridges; not for contribution to public platforms.

Zixi — paid; broadcast contribution; Akamai-owned; competes with SRT/RIST.
Haivision SRT Hub / SST — paid SRT-based services.
Encoding.com / Mux Live / Cloudflare Stream Live — managed services accepting RTMP / SRT / WHIP and outputting LL-HLS / DASH / WebRTC.

Twitch / YouTube to viewers — HLS, 10–30 s. Encoder pushes RTMP/SRT/WHIP, platform delivers HLS.
Self-host Owncast — RTMP in, HLS out, 10–20 s.
Sub-second indie: WHIP in → WebRTC/LL-HLS out via MediaMTX or AntMedia.
TV-style multi-cam studio: NDI on a 1 Gb / 2.5 Gb LAN.
Remote IRL camera over LTE/5G: SRT to your studio NDI router.
Cloud-bridge two studios: SRT or NDI Bridge.
WebRTC video conferencing: see Real-time Video.