Talking about cable technologies

In June, my colleague Steve Lampen gave a number
of successful presentations in Scandinavia and the Middle East. As he explains
to Broadcast Pro Middle East, he concentrates on cable technologies for 4K, 3G
video and Ethernet AVB in his talks

The various audiences were very impressed and I would like to take this opportunity to highlight some of the latest trends in the broadcast market. 

The 4K format

Manufacturers of consumer products are heavily promoting 4K technology. As a result, broadcasters really need to take it seriously. For us, from a cabling perspective, 4K means that the bandwidth is growing, because 4K is 8×1.5 Gb/s or 4x 3 Gb/s or 4x HDMI.

Today this signal is transmitted by using 4 independent connections, commonly referred to as “quad-link”, where each link is a 3G-SDI (3 Gb/s).  That said, we spec the same length that we do for 3 Gb/s signals. Here you find our latest overview of the video distance lengths:

It may be some time before broadcasters will be able to send a 4K signal down a single cable as a 12Gb/s SDI signal.  How long we will have to wait for this will depend in part on IC manufacturers, who today can only support 6Gb/s SDI signals. However, 4K signals could be supported in a “dual-link” mode, as broadcasters do with 3D today.  By the way, Belden offers a solution for this application: 1694D – two cables bonded together. Again, the infrastructure isn’t there today and may never come.  My feeling is that if/when 4K equipment manufacturers move away from supporting quad-link, we will see the market jump to “single-link”, passing right over dual-link.

Some router companies, like Utah Scientific, have announced support for 6Gb/s SDI routers, but I think this is not entirely necessary  in the adoption of 4K infrastructures.  We will need to consider those that do adopt this approach.  As you can imagine, this will have a huge impact in the supported cable lengths when using the conventional 1855ENH or 1694A video cables.  It is a new technology and we will see over the next year what the market will drive, perhaps all change or we will start to see 4k as a compressed signal to make it fit into current infrastructures. All this remains to be seen at this time.

Ethernet AVB standard

The other trend is Audio Video Bridging (AVB), based on the new IEEE Ethernet standards. It is open and interoperable, so any vendor can support it. It is different from other solutions (CobraNet™, EtherSound™, Dante™) which are proprietary solutions on top of Ethernet to deliver latency/guaranteed bandwidth and synchronization.  AVB’s advantages are

  • Synch accuracy of +/-500 Nano sec over 7 hops
  • Latency of 2ms for Class A and 50ms for Class B
  • Complex installs become simple and
  • Multiple vendors

AVB requires an Ethernet switch with AVB supporting chip and software to enable the chip and run AVB protocols. Earlier this year, during NAB in Las Vegas in April, Belden’s IT division, Hirschmann, introduced its first AVB switch in an RSP design.  It is much more compact than the traditional 19” designs!

It would help to have AVnu certification, so it interoperates and AVB endpoints (mic, speaker, console, etc.) must support AVB as well.

AVB will impact other traffic:

  • AVB will take the two highest levels of QoS on the switch
  • AVB defaults to take 75% of a link but can be dialed down to zero
  • AVB can apply to Video as well as Audio singularly or mixed
  • For a converged network: All non AVB traffic (VoIP, IM, Building Control Systems) goes in lower QoS levels and
  • It works with one subnet, seven hops max.

AVB will run over Cat 5 up to 1G and with Cat 6 for 10G over copper.  40G will currently run over fiber. By the way, 10G and 40G are needed for uncompressed video and while it isn’t as attractive as the interfaces themselves, category cable with excellent performance would still be of critical interest, I imagine.


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