RFC 3550 defines what exactly an RTP packet is: ' A data packet consisting of the fixed RTP header, a possibly empty list of contributing sources, and the payload data'. Let's review several basic concepts and extensions over this initial principle. However, as the saying goes, the devil is in the details. Those packets have to be collected and re-assembled, to obtain the media that was originally transmitted by the sender. Participants expecting to receive data will open a UDP port where they listen for incoming RTP packets. Participants wanting to send will partition the media into different chunks of data called RTP packets, then send those over UDP to the receivers. The basic principle behind RTP is very simple: an RTP session comprises a set of participants (we'll also call them peers) communicating with RTP, to either send or receive audio or video.

RTP has surely become a de-facto standard given that it's the mandated transport used by WebRTC, and also lots of tools use RTP for video or audio transmission between endpoints. Our first topic is the Real-time Transport Protocol (RTP), the most popular method to send or receive real-time networked multimedia streams. It is important to have a firm grasp on some basic concepts about RTP, to understand what is going on behind the curtains, so we are able to fix issues when these happen. Of course, ' easier' has to be quoted in the previous paragraph, because the fact is that using these command line tools still requires a good amount of knowledge about what the tool is doing, why, and how. Both of these tools offer libraries meant to be used from your programming language of choice, but they also provide handy command-line tools that become an 'easier' alternative for those who don't want to write their own programs from scratch. Afterwards, we'll see how to leverage this knowledge to build a reliable RTP connection between Kurento and mediasoup:įFmpeg and GStreamer are two of the tools that come to mind for most developers while thinking about writing a quick script that is capable of operating with RTP.

In the next series of posts we'll first talk about how RTP and SDP messages work, and some implementation details in two popular multimedia toolkits: FFmpeg and GStreamer.

Ffmpeg rtsp teardown