Primer: Live-Switched Webcasting
Although it's possible to webcast with a webcam or smartphone and a streaming service provider, a professional live-switched webcast has more in common with a live TV broadcast than it does a kid with a smartphone. This article discusses the roles that must be filled in a live-switched webcast, the various features and types of video switchers, and a lot of the small details that are important considerations in the larger video switching and webcasting workflow.
Webcast Technician
The webcast technician operates the webcast encoder and sends a live video signal to a streaming server or service so that viewers can watch the webcast live over the internet. They monitor both the internet upload speed and webcast output to ensure there are no dropped frames, as well as the live webcast to make sure the audio and video quality are acceptable versions of the send.
The webcast technician can also be responsible for fielding tech support questions and accepting viewer questions for the presenter to respond to.
Camera Operators
All video productions require camera operators, although some productions use multiple robocams that are operated by a single operator with a remote controller. Typically, a traditional video camera operator will be elevated from a live audience on a pair of risers—one for the operator and one for the camera tripod.
A fluid head tripod that is properly balanced and counterbalanced ensures smooth pans and tilts that do not stick or dip. Camera operators can be connected to the technical director with a headset intercom and/or tally light and in some workflows can also monitor an audio input for backup purposes or if their video recording is ever required for a reedit of the live-switch.
Video Switcher Form Factors
All-in-one hardware solutions integrate the control panel and the video switcher, while others separate the two components.
The video switcher component is either housed in a rackmount case or in a computer, and the control panel can either be a software computer interface or a hardware control panel. The two components are connected, typically by an Ethernet cable or Wi-Fi signal.
All-in-one hardware solutions are more portable than individual components, but this also means that all of the cables converge on the video switcher, making them difficult to conceal. It also tends to make the footprint on the tech table much larger. All-in-one solutions also make it more difficult to operate with multiple operators, but this can be a benefit for a technical director who is performing all the previously mentioned roles.
Video Switcher Inputs
HD-SDI is the gold standard for video switcher input connectors, because this single cable can run longer than the equivalent consumer HDMI standard and requires one-third as many cables as the analog component video standard. HD-SDI cable, otherwise known as BNC cable, has a bayonet connector and locks securely, while the other standards are often pulled out accidentally.
Not all BNC cables are created equal. Technically, HD-SDI cable is an RG59 or RG6 coaxial cable, terminated with a BNC connector, and features either or both foil or braided shielding to block out unwanted RFI or RMI. HD-SDI cable must conform to the relevant SMPTE standard: SMPTE 292M requires HD-SDI to have a 1.485 Gbps bandwidth for 1080i, and SMPTE424M requires 3G-SDI to have a 2.970 Gbps bandwidth for 1080p. The 6G-SDI standard, which will be used for 4K, has not been finalized at this writing.
Consumer cameras often lack HD-SDI outputs and computers use HDMI, digital visual interface (DVI), DisplayPort, or video graphics array (VGA), so having a native computer input on the video switcher is a consideration. The alternative is to use a video converter to convert and/or scale a video camera or computer signal to a compliant video switcher input.
It’s also important to note that DVI connectors and cables come in three varieties: DVI-A, DVI-D, and DVI-I. DVI-A is an analog connection and can be converted to VGA with a simple adapter, which is useful when working with legacy workflows, such as with VGA computer inputs.
DVI-D is a digital connection and can be converted to HDMI with a simple adapter, albeit without any ability to embed audio. DVI-I is the best of both worlds and is switchable between digital and analog. A DVI-A cable will not work on a DVI-D connection, although a DVI-I can do both.
The number of video inputs by type and total active inputs is also important to consider. Some video switcher models have more than one available connector type for a given single input, so the number of effective video inputs can be lower than the number of available input connectors.