Testing Compatibility at an S67 Plugfest

As AES67-compliant products continue to come on the market, how can we be sure they are really compatible with each other with no test equipment currently available to verify compliance?

One way is to hold a plugfest where manufacturers of products that incorporate AES67 can get together, hook up their products to each other and see what happens. Such a plugfest was indeed held at the beginning of November 2015 at National Public Radio headquarters in Washington, D.C. This followed up on a previous plugfest held in Munich, Germany in 2014.

The idea of the plugfest is to be able to perform testing in a true engineering environment where ideas can be freely exchanged, said Phil Owens, senior sales engineer, Wheatstone Corp.

Held under the aegis of the Audio Engineering Society, the plugfest was organized with the goal of checking the extent of interoperability of the 13 separate products brought in for testing. The manufacturers that participated were ALC NetworX, Archwave Technologies, Digigram, DirectOut, Lawo, Meinberg Radio Clocks, Merging Technologies, Telos Corp., Wheatstone Corp., and Yamaha Corp.

GETTING DOWN TO BUSINESS

Over the course of the plugfest a series of tests were conducted. The first test checked the ability of the devices to be synchronized to a central grandmaster clock configured for Precision Time Protocol (PTP) as defined by IEEE-1588. Actually two ports of the clock were used, each set to a different PTP domain. One of the grandmaster clock ports was set to PTP domain 0, which is the IEEE-1588 default profile; and the other for PTP domain 1, which is the media profile according to AES67, Annex A. AES67 recommends using this profile, but doesn't mandate it.

Each clock port was connected to a different Ethernet switch, each from a different manufacturer. Then those two switches were connected together so that each PTP domain was available on both switches. In the course of testing, the various devices under test were hooked up to each of the master switches.

The next test checked multicast streaming with multiple devices transmitting streams and multiple devices in turn receiving the streams. A standard stream was used for all tests with its parameters described in Session Description Protocol (SDP).

The third test checked unicast streaming with Session Initiation Protocol (SIP). There are three SIP modes-receive only, send-only and send/receive, that were all tested.

There was also a test checking on the network itself and media clock recovery.

From left: Johan Boqvist (Swedish Radio) in discussion with Greg Shay (Telos Alliance) and Sonja Langhans (IRT). Image courtesy of AES.

LINK:	http://www.tvtechnology.com/audio/0014/testing-compatibility-at-an-aes...
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