As well as the content stream (used for sending to H.323 endpoints), the MCU also generates a Codian proprietary format version of the content channel video which can be viewed in conjunction with
Content channel streaming also allows participants using H.323 video conferencing endpoints without H.239 capability, or SIP endpoints to view a high resolution version of the content channel. Content channel streaming also provides some features not available via the H.239 protocol:
"Markup" is the overlaying of graphics and text onto the content channel video; this could be used, for instance, to draw attention to a specific element of a presentation slide. Markup can only be performed through the content channel streaming interface, and is accomplished via the simple mechanism of clicking and dragging with the mouse, with extra controls for changing the drawing color or clearing the markup when its usefulness has passed.
Content channel markup also has the following characteristics:
All content streaming viewers have equal markup capabilities. This means that either all viewers are able to perform markup on the content channel video (or clear it), or all are unable to do so - it is not possible to restrict markup to just a subset of active viewers.
The video markup, although it can only be edited by streaming viewers, will be seen by content channel streaming viewers, by participants connected via H.323 endpoints that are receiving the content channel, and by any participants that are viewing the content as part of their main video.
Video markup is normally used as an overlay to content channel video as supplied by a H.239, BFCP, or VNC connection. However, for a conference with content channel operations enabled, it is also possible to form a content channel comprising just the markup applied to an otherwise blank video stream. This can be accomplished simply by starting to stream the conference's content channel and performing the usual markup operations on the (empty) content channel displayed. Adding markup to such a blank channel "activates" it, and will cause a video channel to be opened to those H.323 conference endpoints which have H.239 capabilities.
The ability of content channel streaming viewers to perform markup is governed by the
channel video setting on the | page. |
In parallel with, though in many senses independently of, content channel streaming, the MCU also provides a mechanism for those streaming a conference's content channel to communicate with other conference participants via text messages. Beneath the window showing the content channel video, streaming viewers are able to type messages that will be sent to all other streaming viewers, as well as see messages that other users type.
In order that users contributing text messages can be identified, each content streaming viewer has an associated user ID, and this ID is
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