Cisco Cisco TelePresence MCU 4510 Maintenance Manual
Content channel video support
Cisco TelePresence MCU Version 4.2 Printable online help
Page 60 of 252
Content channel video support
The MCU supports an additional video channel known as the content channel for each conference.
This feature encompasses:
This feature encompasses:
H.239 video streams sent from the MCU to viewing H.323 endpoints
Sourcing the content channel from a H.323 endpoint's H.239 video stream, a SIP endpoint
supporting content using BFCP, or a VNC connection
supporting content using BFCP, or a VNC connection
Showing the content as part of the
main video
channel, where an endpoint cannot, for whatever
reason, receive the content channel as an additional video channel. That is, the participant will
see the content as a pane in the conference layout
see the content as a pane in the conference layout
Streaming the content channel to users' desktop machines as a pane in the conference view
Streaming the content channel to users' desktop machines as a separate window (where markup
and text chat can also be used)
and text chat can also be used)
(*)
Allowing graphical and textual "markup" of the content channel
(*)
Text chat between conference participants
(*)
*
- these features require the
web conferencing feature key
.
Content channel vs. main video
The H.239 protocol allows the MCU to support an additional video stream to or from each connected
endpoint. Therefore, there are potentially three media streams between each endpoint and the MCU:
audio, main video and content video.
endpoint. Therefore, there are potentially three media streams between each endpoint and the MCU:
audio, main video and content video.
SIP endpoints will always receive the content as part of the main video channel. That is, SIP endpoints
will not receive the content channel as a separate video channel, but will see the content as a pane in
the main video channel.
will not receive the content channel as a separate video channel, but will see the content as a pane in
the main video channel.
The main video is the normal multi-pane conference view showing participants' video streams
composed within the selected layout. The differences between the content channel video and the main
video are:
composed within the selected layout. The differences between the content channel video and the main
video are:
Single layout
Each participant in a conference can normally select their own individual main video layout (e.g. a
2 x 2 grid of other participants, one large focused pane plus eight smaller panes) and they are
free to change this layout as many times as desired while they are connected to the conference.
By comparison the content channel video always shows just a single video stream, "full screen",
and each viewing endpoint will see the same stream. The stream which constitutes the content
channel can change any number of times during the conference, but there can be at most one
contributing stream at any given moment.
Each participant in a conference can normally select their own individual main video layout (e.g. a
2 x 2 grid of other participants, one large focused pane plus eight smaller panes) and they are
free to change this layout as many times as desired while they are connected to the conference.
By comparison the content channel video always shows just a single video stream, "full screen",
and each viewing endpoint will see the same stream. The stream which constitutes the content
channel can change any number of times during the conference, but there can be at most one
contributing stream at any given moment.
One channel per conference
Each participant's main video stream is encoded independently; this means that each endpoint
can be receiving its main video stream at a different bit rate, codec, or resolution to that being
sent to other participants.
However, there is a single content video stream per-conference: the MCU sends the same bit rate
and resolution to all endpoints receiving content. The bit rate and resolution used is chosen to
maximize the number of viewers - for instance the resolution might be reduced if a new endpoint
joins the conference and its content receive capabilities are more limited than those of the other
participants. Note that in conferences that use encryption, the MCU can send encrypted and
unencrypted content to different participants in the same conference (albeit with the same
encryption key for every participant receiving encrypted content).
Each participant's main video stream is encoded independently; this means that each endpoint
can be receiving its main video stream at a different bit rate, codec, or resolution to that being
sent to other participants.
However, there is a single content video stream per-conference: the MCU sends the same bit rate
and resolution to all endpoints receiving content. The bit rate and resolution used is chosen to
maximize the number of viewers - for instance the resolution might be reduced if a new endpoint
joins the conference and its content receive capabilities are more limited than those of the other
participants. Note that in conferences that use encryption, the MCU can send encrypted and
unencrypted content to different participants in the same conference (albeit with the same
encryption key for every participant receiving encrypted content).
Differing characteristics
The range of bit rates, resolutions and frame rates available to the MCU for sending the content
channel via H.239 to H.323 video conferencing endpoints is potentially as wide as that for the
main video channel. However, in general, the main video channel is used for motion video (i.e.
The range of bit rates, resolutions and frame rates available to the MCU for sending the content
channel via H.239 to H.323 video conferencing endpoints is potentially as wide as that for the
main video channel. However, in general, the main video channel is used for motion video (i.e.