The H.239 Protocol and Content Sharing:
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 supporting documents 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 come new 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.
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 on the main monitor while the presentation (e.g. a Powerpoint presentation) displays on the second monitor as depicted below.
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 a major 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:
Can my local video conferencing system support H.239?
Do I have the necessary peripheral equipment, such as a device to provide the interface between my computer and my video conferencing system, as well as dual monitors to view the dual video streams?
Do I have the appropriate software keys and options activated to enable my video conferencing equipment to use the H.239 features?
Do I have sufficient calling bandwidth to simultaneously support the video and content?
Have I considered the interaction between network devices such as firewalls and my H.239-enabled endpoints?
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?
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 because they 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, but this is not an optimal scenario.) Some additional points to remember are as follows:
Some video conferencing systems, such as the Polycom VSX products, support H.263 and H.264 video protocols as well as H.239, but may be unable to support H.264 and H.239 at the same time. You will want to check your product information or contact your vendor for details about the capabilities of your specific system.
Using features such as H.239 will require software key activation and possibly hardware in order to transmit H.239. Some new endpoints reportedly come with 5 minute trial versions of H.239 causing confusion for users and leading them to believe they have the feature fully enabled on their systems until the demo stops working during a call.
The fact that a device supports the necessary video protocols to receive H.239 content does not necessarily mean that it is configured and/or able to transmit H.239 content.
If you encounter problems configuring and using H.239 and believe your system is capable of supporting it, you are encouraged to consult your equipment documentation, contact your vendor support representative, and/or engage your VITU or other local video support personnel for information and assistance.
People+Content IP is an application that can be downloaded from the Polycom website, installed on a PC, and used to share content over your network. If you decide to use it, you will need to ensure your network and PC work correctly with it and test the application appropriately to ensure reliable operation with the video conferencing equipment.
H.239 and MCU Configuration:
There are two important points to keep in mind when using H.239 in video conferences that utilize the K-20 MGC100 MCUs. First of all, the H.239 option is not turned on by default on the MCUs. The feature must be requested by the event scheduler when the MCU reservation is created, preferably both by entering the request in the Additional Information field in the KORRS event request and by calling the MCU Operations personnel to call attention to the need for H.239 to be activated. Secondly, H.239 uses special video resources on the MCU Video+8 boards, so activating the resources only when they are needed is an important point to keep in mind.
In 2010, K-20 acquired two Tandberg/Cisco MSE8000 MCUs, and these have far greater content sharing resources, along with support for HD, continuous presence, and transcoding on each MCU port. Please contact the MCU staff at 888-934-5553 if you would like to schedule conferences on the MSE8000 MCUs and take advantage of their expanded ‘per port’ resources.
It is crucial for video conferencing support teams to evaluate equipment capabilities/options, configure H.239-capable units appropriately, and verify the status of the equipment in use at partner institutions prior to testing H.239 content sharing technology. Once these tasks have been accomplished, testing H.239 with partner institutions in point-to-point and/or multipoint call configurations is an important part of ensuring success with utilizing the technology. Settings may need to be fine-tuned and other issues may need to be resolved in order to conduct successful H.239 calls. Those who regularly support H.239-enabled calls suggest selecting a specific content sharing approach, documenting it, and applying it consistently throughout your organization. Another important, and often overlooked, aspect of testing is reviewing the content to be shared during the video conference to ensure that colors, font styles and sizes, and graphics are readable in the content sharing environment. If possible, this testing should be done in a test video conference with the exact site configuration that will be used in the live event. Finally, whenever changes to your hardware or software configuration/settings and/or software upgrades are completed on your video conferencing equipment, it is a good idea to test the H.239 capability again to verify that all features are still working correctly.
Backup Plans and Presentation Considerations:
Creating and implementing a backup plan is an important part of supporting advanced content sharing features. One possibility when using some endpoints (such as the Polycom VSX series) may be to ask the MCU staff to disable H.239 on the MCU and lock the conference at H.263. This may enable sites to share content successfully even though the dual-stream feature will not be available. A backup option is to use an S-Video output from your laptop or PC as a camera input on your video conferencing equipment. In this way, you will at least be able to share content by way of a camera input switch in the event you encounter problems with the H.239 channel. Another good idea is to email or deliver copies of presentations to the remote participants ahead of time so they can follow the presentation even if issues develop with content sharing during the event. Through proper evaluation, planning, configuration, testing, and operation, content sharing in general and H.239 in particular can provide valuable tools to enhance the quality of video conferences.
http://www.wa-k20.net/confluence/display/k20VC/Using+Content+Sharing+%28H.239%29 – This is a link to the H.239/Content Sharing thread on the K-20 web site discussion board.
http://www.itu.int/rec/T-REC-H.239/en - Visit this site to obtain more detailed information about the ITU-T H.239 Recommendation.
NTSC Video Working Group 10/11/2011