The challenges around telepresence interoperability are related to both logistics and technology. Logistics are probably the bigger problem. Vendors usually conduct interoperability tests by gathering at an interoperability event, bringing their equipment to a meeting location, and running test plans with each other. This is the way IMTC manages H.323 interoperability tests and also the way SIPit http://www.sipit.net/ manages tests based on the SIP protocol. While developers can pack their new video codec in a suitcase and travel to the meeting site, multi-codec telepresence systems are large and difficult to transport. A full-blown telepresence system comes on a large truck and takes substantial time to build – usually a day or more. Therefore, bringing telepresence systems to interoperability test events is out of the question.
An alternative way to test interoperability is by vendors purchasing each other’s equipment and running tests in their own labs. While this is acceptable approach for $10K video codecs, it is difficult to replicate with telepresence systems that cost upwards of $200K. One could ask “Why don’t you just connect the different systems through the Internet for tests?” The issue is that telepresence systems today are run on fairly isolated segments of the IP network - mostly to guarantee quality but also due to security concerns - and connecting these systems to the Internet is not trivial. It requires rerouting network traffic, and use of video border proxies to traverse firewalls.
The technology challenges require more detailed explanation. Vendors like HP and Teleris run closed proprietary telepresence networks and their telepresence systems cannot talk directly to other vendor’s systems. There are of course gateways that can be used for external connectivity but gateways mean transcoding, i.e. decrease of quality, limited capacity, and decreased reliability of end-to-end communication. For those not familiar with the term ‘transcoding’, it is basically translation from one video format into another video format. Telepresence systems send and receive HD video at 2-10 megabits per second (Mbps) for each screen/codec in the system, and all that information has to go through the gateway and be translated into a format that standards-based systems can understand.
Some telepresence vendors state that they support standards such as H.323 or SIP (Session Initiation Protocol). However, standard- compliance is not black-and-white, and telepresence systems can support standards and still not allow good interoperability with other vendors’ systems. When Cisco introduced its three-screen CTS 3000, they made the primary video codec multiplex three video streams – its own and the two captured by the other two codecs – into a single stream that traversed the IP network to the destination’s primary codec. Third-party codecs cannot understand the multiplexed bit stream, and that is basically why you cannot connect a Polycom, LifeSize, or Tandberg telepresence system to Cisco CTS. Note that Cisco uses SIP for signaling and claims therefore standard-compliance; however, the net result is that third-party systems cannot connect. If you decide to spend more money and buy a gateway from Cisco, you could connect to third-party system but at a decreased video and audio quality that is far from the telepresence promise of immersive communication and replacement of face-to-face meetings. The discrepancy between the ‘standard compliance’ claim and the reality that its systems just do not talk to any other vendor has haunted Cisco since they entered the video market.
When Tandberg introduced its three-screen telepresence system T3, they made another technological decision that impacts interoperability. T3 combines the video streams from three codecs (one per screen) into one stream, and any non-Tandberg system that connects to T3 receives what we call a ‘filmstrip’, i.e. three small images next to each other (http://www.flickr.com/photos/20518315@N00/4015164378/). The ‘filmstrip’ covers maybe one-third of one screen (or one-ninth of the total screen real estate of a three-screen system). So, yes, you can connect to T3 but you lose the immersive, face to face feeling that is expected of a telepresence system. Note that T3 uses standard H.323 signaling to communicate with other systems, so it is standard-compliant; however, the result is that if you want to see the three images from T3 on full screens, you have to add an expensive Tandberg Telepresence Server (TTPS). I will discuss TTPS in more detail in parts 4 and 5.
To come back to my original point, due to a range of logistical and technological issues, establishing telepresence interoperability is quite a feat that requires serious vendor commitment and a lot of work across the industry.
Stay tuned for Part 3 about the organizational issues around telepresence interoperability testing … http://videonetworker.blogspot.com/2009/10/telepresence-interoperability-part-3.html