Video live streaming is the ability to allow the video from your DSLR / mirrorless camera or camcorder to appear in real time on web-based platforms such as Zoom, Facebook Live, YouTube Live, Twitch, Ustream and more.
Live streaming is possible with many cameras. All the major camera brands now offer free web streaming utility software to use with some of their most current models. This software negates the need for a 3rd party video capture device between the camera and computer. Cameras that are not compatible with the camera brand web utility software will need the additon of a video capture device.
The one most important component the camera must have is an HDMI out port. This is the same type of connection found on all modern televisions although it comes in a few different sizes (full, mini and micro) depending which camera you have. Your desktop or laptop computer will also need to have an HDMI connection if you want to connect directly from the camera. Some newer models allow streaming via USB cable.
HDMI connections only allow the transfer of video data of most camera models. Therefore you will need an external microphone (for better audio than the computer microphone) connected to the computer to transmit the audio.
You will also want a camera that allows 'clean HDMI out' meaning a video transmission that is free of the camera setting information overlays you normally see while filming with the camera alone.
Once you have the pieces you need you will choose a streaming platform and follow the instructions laid out in the web utility streaming software for enabling a connection.