Video over IP

Video over IP means carrying broadcast-quality video and sound over ordinary computer networks, using the internet protocol (IP), instead of over special video cables. IP is the set of rules by which computers send data to each other in small pieces called packets. Once video travels as packets, the equipment that handles it can become software, and that software can run in the cloud.

For decades, every camera, recorder and screen in a TV studio was joined by its own special video cable. A large hardware switch connected the cables, and each cable carried one signal in one direction. Adding a camera meant laying a new cable.

Here is how video over IP works in general. A camera, or a small device beside it, cuts the video signal into packets. Each packet carries a timestamp. Ordinary network switches, of the kind used in data centres, carry the packets to any destination on the network. Every device follows one shared clock, so that the video from twenty cameras and the sound from forty microphones stay exactly in step. The receiver, which may be a hardware screen or software in the cloud, rebuilds the picture. Inside a studio, the video is usually sent uncompressed, which needs about 1.5 gigabits a second for one HD signal. Over long distances it is compressed, and special protocols resend lost packets, so that no frames are missing. Delay matters more than anything: a director cutting between cameras cannot wait even a second. This is a question of bandwidth and latency.

Take, for example, a TV studio. Its broadcast video router used to be a large box full of cables, and it is now increasingly software that directs packets across network switches.

Consider a cricket match at a hill-town stadium. With remote production, the cameras at the ground send their feeds over a fibre network to a control room in another city, and no outside-broadcast truck is needed.

Say a hospital wants medical students to watch an operation. The cameras in the operating theatre send their video over the hospital's own network to a lecture hall, with almost no delay.

How is video over IP different from video streaming? Streaming to viewers, as in adaptive bitrate streaming, compresses the video heavily and lets it arrive a few seconds late. Video over IP inside a studio must arrive within milliseconds, at full quality. It is also how a cloud playout system receives its programmes. The same idea carries phone calls as VoIP.