What is RTMP?

Real-Time Messaging Protocol (RTMP) is a protocol developed by Macromedia (which is now Adobe) for the transmission of audio, video, and other data over the Internet. RTMP is most commonly used to stream content in real-time over the internet.

Originally, RTMP was designed to be used between a Flash player and a server. A persistent connection is maintained between the Flash player and the server, allowing for the direct transmission of audio, video, and other data between the two.

There are several variations of RTMP, including:

1. RTMP proper: The standard protocol for streaming audio, video, and data over the internet, using a persistent, stable connection.

2. RTMPT (RTMP Tunneled): Wrapped in HTTP requests to traverse firewalls.

3. RTMPS (RTMP Secure): Uses SSL/TLS for security encryption.

4. RTMPE (RTMP Encrypted): A proprietary (and deprecated) variant that includes some level of encryption.

5. RTMFP (RTMP Flow Protocol): Uses UDP instead of TCP for lower latency.

Despite its age and the decline in the usage of Flash technology, RTMP is still widely used for live streaming and is often employed as the video ingest protocol in many modern streaming platforms. It is notable for its low-latency streaming capability which makes it a good choice for live broadcasts or other real-time events. However, as it is not as compatible with modern mobile and HTML5 platforms, RTMP streams are often repackaged into other formats (like HLS or DASH) for delivery to the viewer's device.