250 The Digital Filmmaking Handbook, 4E

Digital Video Cables and Connectors

Building an editing system is much easier than it used to be, but it helps to know the different ins and outs of your gear (see Figure 11.9)

Balanced Audio In (2 channels via XLR)

Figure 11.9

A breakout box, like this one from AJA Kona, offers many different ins and outs to make it easy to hook up your gear.

FireWire

FireWire was developed by Apple in 1986 as a replacement for several older interfaces: serial, parallel, SCSI, and, to a lesser degree, Ethernet. Nowadays, many computers only have two interfaces for connecting peripherals: USB for slow devices such as keyboards, mice, and printers, and FireWire 400 or 800 for high-speed connectivity to mass storage, cameras, scanners, and even networks since FireWire allows you to daisy-chain up to 64 devices.

HDMI

High-definition multimedia interface (HDMI) is designed to transmit uncompressed digital media to computers, television sets, and other media devices. HDMI is great, but the cables do not lock into place, which can make them unstable when used with hardware such as cameras.

SDI and HD-SDI

Developed by Sony as an interface between high-end digital video formats and non-linear editing systems, SDI (for Serial Digital Interface) is designed to handle uncompressed digital video and provides a data rate ranging from 140Mbps to 570Mbps. SDI supports much longer cables than FireWire does, which is useful for postproduction facilities that keep their equipment in a special climate-controlled machine room and need to send high-quality video signals to other rooms in the building. HD-SDI has a data rate of 1.485Gbps (Gigabits per second), which is necessary for moving uncompressed HD data. SDI uses BNC connectors that lock into place for maximum stability.

Fibre Channel

Fibre Channel is a high-speed data transfer protocol that is currently the most popular solution for networked editing workstations. Fibre Channel is similar to Ethernet but with greater bandwidth, supporting up to 4Gbps data transfer rates, which means that SANs using Fibre Channel connectivity can support real-time transfer of HD video and maintain synchronization of audio and video streams.

Thunderbolt

Thunderbolt is a new high-speed I/O protocol developed by Intel and Apple that can handle 10Gbps in data transfer. That’s more than five times faster than HD-SDI. It was specifically designed for professional audio and video applications, where high data transfer rates with accurate synchronization is crucial for real-time playback and processing. The Thunderbolt interface can support multiple daisy-chained devices, so in theory at least, you’ll be able to use a single port on your computer to connect HD displays, drives, cameras, audio mixers, and any other part of an editing system together. At the time of this writing, Thunderbolt is brand new technology so look for new products and developments to take advantage of it in the very near future.

RS-422

If you are using a high-end VTR, you’ll need support for an RS-422 cable to remotely control the deck via your computer. RS-422 is a serial device protocol that is found on almost all high-end VTRs.

Audio Interfaces

The cables and connections listed in the preceding section carry both audio and video signals, but there are also several audio-only interfaces out there.

TRS is the standard audio interface used with earbuds, iPods, cell phones, and other small devices. It is an analog, consumer-grade audio interface. Some higher-end audio devices and cameras, though, use BNC or XLR connectors. If you find yourself trying to connect a TRSequipped device into something that only has BNC or XLR connectors, then you’ll need to get appropriate adapters. RCA is another type of consumer-grade audio connector used a lot in older television sets, video decks, and home stereos.

If you’re working with a high-end digital audio device, it might have a digital interface such as SP/DIF or AES/EBU, in addition to an RCA or XLR interface. (Note that some SP/DIF or AES/EBU connections use the same cables—RCA, BNC, or XLR—to carry a digital audio signal.)

If you need to take audio from a mixer or microphone, you’ll probably need XLR connectors.