Explanation/Reference:
Reference: http://www.cisco.com/c/en/us/about/press/internet-protocol-journal/back-issues/table-contents-
57/153-binary.html
http://www.cisco.com/c/en/us/td/docs/telepresence/infrastructure/articles/ cisco_telepresence_enable_dual_video_duo_people_content_h239_codian_kb_69.html Explanation:
Protocol Details
The basic concept of floor control is analogous to managing a live in-person presentation, where you want to control who is presenting, manage and transition your presenters, and maintain a feedback loop. Also important is the ability to allow a presenter to show slides and share with your audience a white board or transparency projector.
Dual video, Duo Video, People + Content and H.239 are all terms that describe support for a second live video channel in an H.323 call. Such a channel is most often used for the transmission of content, like the screen of a presenter's PC (so the term 'content channel' is also used). The terms all have slightly different meanings. Dual video is a generic term describing this capability. Duo Video and People + Content are proprietary implementations from Cisco TelePresence and Polycom respectively.H.239 is the ITU standard for a second video channel; this is supported by all the major vendors, and is the only content channel standard supported by Cisco acquired Codian products or Cisco TelePresence Serial Gateway Series products on H.323 video calls.