h.239

The H.239 Protocol and Content Sharing:

Challenges and Considerations



Introduction:

Content sharing in one form or another has been around almost as long as video conferencing itself. A natural extension of the interaction that results from being able to see and hear participants at remote locations is the desire to enhance that interactivity with the ability to show supportingdocuments and various forms of graphics and presentation materials. In the early days of video conferencing, content sharing was often as simple as switching to a document camera input or pointing a camera at a projected image in the room. Today, H.239 content sharing is enhancing the video conferencing experience in ways that could only be dreamt of ten years ago. Yet, along with new capabilities comenew challenges that must be addressed and managed in order for 21st century video conferencing to meet the needs of end-users and reach its true potential.

Background:

When used as part of a complete end-to-end solution that supports it, H.239 content sharing enables a site to share both local video and a presentation over a content channel simultaneously, so the video image can be seen onthe main monitor while the presentation (e.g. a Powerpoint presentation) displays on the second monitor as depicted below.

[pic]
Before H.239 was adopted as an industry standard there were a couple of proprietary features that provided similar functionality. Polycom implemented People+Content and Tandberg developed DuoVideo – the problem was that without a standard, compatibility became amajor impediment to the use of this type of content sharing. The ITU-T published a recommendation based on the Polycom version of this technology as H.239 in July 2003, with the goal of creating an industry standard that would facilitate cross- vendor compatibility for modern content sharing. The degree of compatibility still varies quite a bit based on factors including make, model, software version,configuration of the endpoints and, in multipoint calls, the MCU or MCUs supporting the call.

Determining the Feasibility of Using H.239:

The initial questions to ask yourself when considering the use of H.239 content sharing are as follows:

1. Can my local video conferencing system support H.239?
2. Do I have the necessary peripheral equipment, such as a device to provide theinterface between my computer and my video conferencing system, as well as dual monitors to view the dual video streams?
3. Do I have the appropriate software keys and options activated to enable my video conferencing equipment to use the H.239 features?
4. Do I have sufficient calling bandwidth to simultaneously support the video and content?
5. Have I considered the interaction betweennetwork devices such as firewalls and my H.239-enabled endpoints?
6. Do the other locations I plan to partner with using H.239 content sharing have all of these capabilities in place and configured as well?
7. Have I verified that the H.239-enabled endpoints at the partner locations are compatible with my own equipment and the K-20 MCUs?

The questions above are important partly becausethey underscore the need to know your video conferencing equipment, its capabilities, and your local configuration before contacting other institutions about using H.239 content sharing or conducting testing. Legacy equipment that supports only H.261 video protocols will not be able to send H.239 content or display the content reliably in an H.239-enabled call. Depending on how an event is set up,these devices may also cause the entire call to re-negotiate to H.261 when they connect and prevent anyone on the call from seeing the H.239 content. (A possible workaround for this is to place the legacy endpoints in a separate cascaded conference with transcoding enabled to allow them to participate in the video portion of the call without preventing the other devices from content sharing,...