WIRELESS TRANSMITTERS GE AR .
W e’ve been sending we can send video through walls, and use mobiles as bring-your-own monitors. But not all solutions are created equal. The earliest wireless video transmitters used for film and television were designed for conventional, analogue, standard- definition TV signals, with all the wobbliness that implies. As we’ve passed through HD, higher frame rates and now 4K pictures, moving pictures by radio for almost a century, and on-set for decades. Now the market has both created incumbents and provoked new ideas – and with them, a desperate need to understand the underlying technology. Speaking of incumbents, Teradek has not allowed success to stifle innovation. As perhaps the most common purveyor of low- latency options, the company has long since added 4K to the Bolt line, including the recent Bolt 4K LT that comes in either 750ft (£2592) or 1500ft (£4635) range options. With SmallHD and Teradek both organs of Vitec, it’s no surprise to see the Bolt 4K Monitor Module built specifically to ride aboard SmallHD’s Smart 7 monitor range.
Beyond point-to-point wireless links, Teradek offers the RT lens control system and an increasing amount of computer network integration. Some of this, particularly the Vidiu X, is designed to work more or less as a standalone encoder, but there’s also options to stream video via mobile phones or, further, on wires. This has become particularly relevant with the need to leave people at the office during this pandemic. DEMOCRACY If we can tolerate a few frames of delay, Accsoon offers several effective and economic options. The range includes the CineEye 2S Pro (£611), which transmits HDMI and SDI on both the 2.4GHz and 5GHz spectrum. On film sets, these unlicensed bands often become busy, and there’s no harm in having access to both. Range is around 1000ft, with power via NP-F battery or coaxial DC input. Latency is kept down to about 60ms, assuming 60-frame video, which is usable for certain kinds of operation. The CineEye 2 Pro (£550) saves by omitting SDI. The CineEye 2S (without the Pro) is a very different device, designed to stream video to mobiles. Ubiquity aside, mobile
NEW TECH SmallHD monitors (above) fit the Teradek Bolt 4K Monitor Module, while the Vaxis Atom 500 (right) works up to 500ft
Compression and latency
Anyone who has used YouTube might instinctively propose the same technology for wireless video – compress the video and send it over Wi-Fi. Video links intended for low latency won’t use the same protocol as Wi-Fi, which implies a certain minimum delay, but conventional codecs can work. One such as H.264, which leverages differences between frames, needs a handful of frames to work with, and imposes a certain minimum delay. Even so, compressed data links can do a good job if the design pays enough attention to minimising latency. Often they seem snappier when sending higher frame rate video, since the delay may be a fixed number of frames – rather than a fixed time.
47. SEPTEMBER 2021
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