ITU-T Recommendation

C.

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.

Cisco acquired Codian products need to be configured to enable H.239

Any H.323 endpoint that also supports the H.239 protocol can source this channel, as can a VNC connection, though some endpoints need to be configured to use H.239 instead of their proprietary solution.

The ITU-T is a standardization sector of the International Telecommunication Union (ITU) responsible for developing and maintaining telecommunication standards. The H.320 series of ITU-T recommendations provides standards for video conferencing over Integrated Services Digital Network (ISDN) and other circuit-switched networks.

Answer C, H.239, defines the procedures for using more than one video channel in H.320-based systems. H.239 is a standard that enables the use of dual video streams in video conferencing systems. This feature allows a presenter to share content such as a presentation or document, while simultaneously showing their video stream.

H.324 (Answer A) is a standard for video communication over low-bit-rate multimedia communication services such as the Public Switched Telephone Network (PSTN). H.230 (Answer B) is a standard that specifies the signaling and control protocol for multimedia communications over ISDN. H.264 (Answer D) is a video compression standard that is widely used for video conferencing, streaming, and other applications. H.329 (Answer E) is not a valid ITU-T recommendation.