How do you hook up 2 video cameras to computer through a audio - video control box for ustreaming so you can switch between two cameras during broadcast?

Answer 1

Switching between video sources sounds like such a simple task but is anything but. Unlike audio signals, video signals are delivered as frames. Each frame has a known starting point and a defined length. Switch from one video source to another and suddenly, the timing for the start of the next frame is not where it should be and the picture breaks up while the computer (or other receiver) sorts out the timing again.

There are two ways to do it and both tend to be expensive. The first is to use a broadcast timing signal called "genlock". It is a signal that is fed to cameras, video players, graphics generators and all other equipment to make sure that they are all producing images at exactly the same time. Genlock is nothing more than a video signal without a black picture so it's easy to generate. Unfortunately, to use it demands that the cameras have a genlock input. Professional cameras have them. Domestic cameras don't. If you have the right cameras, then a video switcher that switches during the vertical interval part of the signal will provide a clean cut.

The second method is to use a small vision mixer (also often called a switcher in North America). Some of the semi professional mixers will take care of synchronizing the signals. The feature that is most important is the "input frame store" or input "time base corrector". They are an indication that non genlocked sources can be used. Some older units such as the Panasonic MX30 and MX 50 units have this feature and are available for only a few hundred dollars. Expect new mixers to start at around $1000 upwards.