AS IP-BASED OPERATIONS SPREAD , ETHERNET IS HERE TO STAY BUILDING BLOCKS FOR STUDIO VIDEO OVER IP
By SCOTT BARELLA , CHIEF TECHNOLOGY OFFICER , UTAH SCIENTIFIC
As the broadcast industry continues its march toward a future defined by all-IP-based operations and driven by commodity IT systems , it ’ s amusing to consider that the whole thing hinges on a technology rooted in the early 1970s . Tracing its origins to the Bob Metcalf / David Boggs project at Xerox PARC , Ethernet became an IEEE standard for LAN , MAN , and WAN networking back in 1983 — long before the internet was anything close to a household word .
Fast-forward to today , when it ’ s difficult to imagine any type of network that doesn ’ t rely extensively on Ethernet . In television studios , Ethernet was traditionally delegated to configuration and control networks . More recently , Ethernet has offered a vehicle to carry compressed transport streams , introducing a new way of thinking and a departure from the older pulse-based streams for carrying compressed video using Asynchronous Serial Interface ( ASI ).
Now , Ethernet is once again the star as the broadcast industry undergoes its latest transformation . Soon , digital SDI signals will be replaced by Ethernet packets transported over all-IP-based networks . With the new SMPTE ST 2110 standard for uncompressed IP video and audio about to come online , it behooves broadcast engineers to have a broad and deep understanding of Studio Video over IP ( SVIP ) in the uncompressed domain using Ethernet .
While there are many aspects to the use of Ethernet for SVIP , only a few key pieces — IP , UDP , and RTP timestamped packets — relate to elementary audio , video , and data streams . A keen understanding of these elements will put engineers far down the road in their ability to manage the new IP topologies for video and audio .
MULTICAST SVIP
First , let ’ s take a look at the basic structure of Ethernet – beginning with subnetworks ( aka subnets ). These use a four-octet address scheme ( for example , the private address of 192.168.1.10 ), followed by a netmask of 255.255.255.0 to further divide the network into smaller sizes in the address range . Within a subnet , any address can “ speak ” with another address as long as the second address uses the first three octets ; e . g . 192.168.1 . X . Some organizations connect themselves using a wide area network ( WAN ) to carry data from different subnets within their private network . To give an example , a station in Denver might need to deliver data to an affiliate station in New York . The Denver LAN subnet might be 192.168.1.0 but the one in New York might be 192.168.20.0 . The WAN would make it possible for these two subnets to communicate .
The previous example is an Ethernet unicast connection in which the address acts as the sender and another address within the subnet acts as the listener . But broadcasting – by its very definition
Broadcast Beat Magazine • www . broadcastbeat . com • 85