Video Streaming Protocols: HLS, DASH, WebRTC, RTMP and SRT

Video streaming protocols are the rules that move video from an encoder to a server, and from that server to each viewer's player. Some carry a live feed in (RTMP, SRT, WHIP), others deliver it out (HLS, DASH, WebRTC), and the pair you pick sets your delay.

TL;DR:

• Ingest protocols (RTMP, SRT, WHIP) push one feed from your encoder to a server, and delivery protocols (HLS, DASH, WebRTC) fan it out to viewers.
• HLS and DASH cut video into small HTTP files that any CDN can cache, which is why they scale to huge audiences.
• WebRTC sends frames as they are encoded, so it reaches sub-second delay but needs media servers to fan out.
• HLS, DASH and RTMP run on TCP, while SRT and WebRTC run on UDP and recover lost packets themselves.
• AIOZ Stream takes RTMP in, plays live video over HLS, and packages on-demand video as HLS or DASH.

What are video streaming protocols?

A video streaming protocol defines how media is split, addressed, requested and sent across a network so that playback can start before the whole file arrives. It sits one layer above the codec (H.264, H.265, AV1), which compresses the pictures, and the container (MP4, MPEG-TS, fMP4), which wraps them with audio and timing. For those lower layers, see how MP4, WebM and other containers differ.

Most live pipelines use two protocols. The first mile, called contribution or ingest, carries one high-quality feed from your encoder to a platform, while the last mile, called delivery, carries many copies to phones, browsers and TVs. A common pairing is OBS sending RTMP to a server, which transcodes the feed and serves it to thousands of viewers as HLS.

This page walks the field cluster by cluster, and the video streaming glossary defines every acronym you'll meet.

Ingest protocols: RTMP, SRT and WHIP

RTMP (Real-Time Messaging Protocol) came from Macromedia and later Adobe, which published its last specification in December 2012. It runs over TCP and once powered Flash playback in the browser. Flash is gone, but RTMP survived as the default way encoders push live video, because almost every encoder and platform still speaks it. The Enhanced RTMP project extends it with newer codecs such as HEVC and AV1. If you stream from OBS, you probably use RTMP already, as our OBS setup guide with RTMP URL and stream key shows.

SRT (Secure Reliable Transport) is an open-source protocol from Haivision that runs on UDP. When a packet goes missing, the receiver asks the sender to resend it, and SRT holds a constant end-to-end latency so those resends fit inside a fixed delay. The stream can also be encrypted with 128, 192 or 256-bit AES. Broadcasters use SRT to send contribution feeds over the public internet, where packet loss would stall a TCP link.

WHIP (WebRTC-HTTP Ingestion Protocol) became RFC 9725 in March 2025. It opens a WebRTC publishing session with a single HTTP POST, so a browser or encoder can send with WebRTC's low delay, and OBS Studio has offered WHIP output since version 30.0 in November 2023. RTSP, revised as RTSP 2.0 in RFC 7826, still runs many IP cameras and security systems.

HTTP delivery: HLS, DASH and LL-HLS

HLS (HTTP Live Streaming), defined in RFC 8216, splits video into short segments and lists them in a text playlist with the .m3u8 extension. The player reads that playlist, then fetches each segment over plain HTTP. Because every segment is an ordinary file, any CDN edge node can cache it, so a million viewers mostly hit caches rather than your origin. Our guide to M3U8 files and HLS segmentation walks through a real playlist line by line.

MPEG-DASH is the ISO/IEC 23009 standard built on the same idea, with an XML manifest called the MPD and support for any codec. The two differ mainly in manifest syntax and device support, as our HLS vs MPEG-DASH comparison shows, and CMAF segments can let one set of files serve both. Each format lists several bitrates of the same video, and the player switches between them as your bandwidth changes, which is adaptive bitrate streaming.

The cost of HTTP delivery is delay. RFC 8216 tells players not to start a live stream less than three target durations from the end of the playlist. With the 6-second segments Apple uses as its example, a standard HLS viewer therefore starts at least 18 seconds behind the live edge. Low-Latency HLS adds partial segments: Apple's example publishes 200-millisecond parts inside 6-second segments with the EXT-X-PART tag. Read how Low-Latency HLS works and when to use it for the full mechanics.

When do you need WebRTC instead of HLS?

You need WebRTC when viewers must respond to the stream within about a second, as in video calls, live auctions or co-watching. WebRTC is the browser's real-time media stack, standardized by the W3C and IETF and summarized in RFC 8825. It sends encrypted frames, usually over UDP, as soon as the encoder produces them, with no segments to fill and no playlist to poll.

The trade-off is scale, because each WebRTC viewer holds a live connection and large audiences need forwarding servers called Selective Forwarding Units (SFUs). Our HLS vs WebRTC decision guide compares latency, cost per viewer and device reach. For how real-time sessions connect people, see WebRTC mesh, SFU and MCU topologies. A common hybrid puts the hosts on WebRTC and mirrors their stage to HLS for everyone else.

Do streaming protocols use TCP or UDP?

Both, and that choice explains most of the latency gap between them. TCP delivers every byte in order and resends anything lost, so one missing packet holds up everything behind it. That's acceptable for HLS, DASH and RTMP, because their players and servers keep a buffer.

UDP sends packets with no delivery guarantee, so the protocol on top has to deal with loss. SRT resends missing packets within its fixed latency, while WebRTC conceals small gaps and lowers its bitrate. QUIC (RFC 9000) also runs over UDP and carries HTTP/3, and the IETF's Media over QUIC working group is building MoQ on it for CDN-style fan-out at near real-time delay. The same TCP and QUIC trade-offs appear outside video, as our Pin hub shows in how IPFS uses TCP and QUIC transports.

Latency by protocol

Each protocol sets a different floor, but the delay you see also includes capture, encoding, transcoding and the player's buffer, as the table shows.

To measure the total yourself, follow our guide to glass-to-glass latency and how to measure it. For live events on a node network, see how decentralized live streaming works.

In this pillar

HTTP adaptive streaming

• What Is an M3U8 File? How HLS Video Segmentation Works: master and media playlists, segments and renditions.
• HLS vs MPEG-DASH: Differences and When to Use Each: manifests, codecs, device support and CMAF.
• What Is Low-Latency HLS (LL-HLS) and When to Use It: partial segments and faster playlist updates.

Real-time and contribution protocols

• HLS vs WebRTC: Which Streaming Protocol Should You Choose?: latency, scale and cost per viewer.
• WebRTC Mesh vs SFU vs MCU: Video Call Topologies Compared: how real-time sessions connect participants.

Latency

• Glass-to-Glass Latency: What It Is and How to Measure It: the stages of delay and a stopwatch test.

How AIOZ Stream handles it

We built AIOZ Stream's live path on RTMP in and HLS out. You create a stream key and point OBS Studio or PRISM Live Studio at the RTMP server URL, and your viewers watch over HLS in the AIOZ player or an embed. The player toolbar adds a Low Latency Mode (Beta) for interactive broadcasts such as Q&A, auctions or gaming. For on-demand video, each quality you request is packaged as HLS (MPEG-TS or MP4 segments) or DASH (fMP4), and the API returns an hls_url and a dash_url.

You can also create a live session through the API; this request is quoted from the docs and was not run here:

curl --location --request POST 'https://api.aiozstream.network/api/live_streams/key_id/streamings' \
  --header 'accept: application/json' \
  --header 'stream-public-key: your_public_key_here' \
  --header 'stream-secret-key: your_secret_key_here' \
  --data-raw '{
    "title": "live_streaming_title",
    "save": true,
    "qualities": [
      { "resolution": "360p", "type": "hls", "container_type": "mpegts" },
      { "resolution": "720p", "type": "hls", "container_type": "mpegts" }
    ]
  }'

The response returns the session's hls_url, player_url and iframe embed. The OBS guide states "Protocol support: RTMP only", and the docs list no SRT, WHIP or WebRTC ingest endpoint and no latency figure for Low Latency Mode. Start with the Create Livestream guide to get your stream key and RTMP URL.

Frequently Asked Questions

Is HLS a protocol or a file format?
Both, since RFC 8216 defines the playlist format and the rules a client follows to fetch segments, while HTTP does the transport underneath.

Which video streaming protocol has the lowest latency?
WebRTC, usually under a second, because it sends frames as they are encoded; LL-HLS comes next at a few seconds, then standard HLS and DASH.

Is RTMP still used?
Yes, mostly for ingest: browsers no longer play RTMP, but most encoders and live platforms still accept it, and AIOZ Stream's live ingest is RTMP.

Is SRT better than RTMP?
Over long or lossy links usually yes, because SRT recovers lost packets on UDP within a set delay, while RTMP wins on compatibility because more platforms accept it.

Can one stream use several protocols?
Yes, and most do: a typical live stream arrives over RTMP or SRT and leaves as HLS or DASH.

Related Reading

• Live Streaming on AIOZ Stream: The Complete Setup Guide: RTMP ingest and HLS playback end to end.
• What Is Adaptive Bitrate (ABR) Streaming? How ABR Works: how players pick a rendition.
• Video Transcoding Basics: H.264 vs H.265 (HEVC) vs VP9: the codecs inside every stream.

References

• RFC 8216: HTTP Live Streaming
• Apple: Enabling Low-Latency HLS
• MPEG-DASH (ISO/IEC 23009)
• Adobe RTMP Specification 1.0 and Enhanced RTMP
• Haivision SRT
• RFC 9725: WHIP
• OBS Studio 30.0.0 release notes
• RFC 8825: WebRTC overview
• RFC 9000: QUIC and the IETF MoQ working group
• AIOZ Stream docs: OBS setup, viewing and sharing, Streamings API, Video API, HLS vs WebRTC