RTMP

What is RTMP?

Real-Time Messaging Protocol (RTMP) is a protocol for streaming audio, video, and data over the internet. RTMP ensures that large media files are segmented into small data packets so that they’re easier to send over a network. Many live streaming and online broadcasting services rely on RTMP to deliver content to users and function properly.

Origins and purpose of RTMP

RTMP was originally developed by Macromedia, which was later acquired by Adobe. It was designed to deliver on-demand and live media to Adobe Flash applications, which were prevalent on the web at the time. The protocol uses a persistent connection to allow low-latency communication, making it ideal for streaming online video and audio content in real time.

While Flash has largely been phased out, RTMP remains a popular choice for streaming due to its reliability and efficiency. It's used by many major streaming platforms, including YouTube Live, Twitch, and Facebook Live.

How RTMP works

Establishing a connection

RTMP operates over TCP, a protocol that ensures reliable delivery of data over the internet. When an RTMP session begins, the client and server establish a connection using a handshake process. This involves exchanging control messages to confirm the connection and set parameters for the session.

Once the connection is properly set up, the client can send a 'play' command to start receiving data. The server then begins to send packets of audio, video, and other data to the client.

Data transmission

RTMP uses a stream of chunks to deliver data. Each chunk carries a payload of audio, video, or data. The size of these chunks can be adjusted during a session to optimize for network conditions. This flexibility is one of the reasons why RTMP is so effective for live streaming.

RTMP also supports multiplexing, which allows multiple streams to be sent over a single connection. This feature is especially useful for broadcasting multiple camera angles or audio tracks.

Advantages and disadvantages of RTMP

Advantages

The main reason RTMP is used for data transfer is its low-latency performance. This makes it ideal for live streaming, where delays between the broadcaster and viewer can be disruptive. The protocol's support for multiplexing and adjustable packet size also contribute to its versatility as streaming technology.

Another advantage of RTMP is its wide support. It's compatible with most streaming software and platforms, making it a reliable choice for broadcasters.

Disadvantages

RTMP has some limitations as well. One is that it's not natively supported by most modern web browsers due to Adobe Flash being phased out. This means that RTMP streams typically need to be repackaged into another format, such as HLS or DASH, for playback in a browser.

RTMP also lacks support for encryption, which can pose security concerns. While it's possible to use RTMPS, a secure version of the protocol, this isn't universally supported and can possibly create more latency.