Cisco Cisco TelePresence MCU 4510 Maintenance Manual
Related Topics
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Content Channel Video Support
The MCU supports an additional video channel known as the content channel for each conference. This feature
encompasses:
encompasses:
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H.239 video streams sent from the MCU to viewing H.323 endpoints
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Sourcing the content channel from an H.323 endpoint's H.239 video stream, a SIP endpoint supporting
content using BFCP , or a VNC connection
content using BFCP , or a VNC connection
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Streaming the content channel to users' desktop machines as a pane in the conference view
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Streaming the content channel to users' desktop machines as a separate window (where markup and text
chat can also be used)
chat can also be used)
(*)
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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
receive the content channel as an additional video channel. That is, the participant will see the content as a
pane in the conference layout
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Content
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Allowing graphical and textual "markup" of the content channel
(*)
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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.
Therefore, there are potentially three media streams between each endpoint and the MCU: audio, main video and
content video.
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:
selected layout. The differences between the content channel video and the main video are:
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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.
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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).
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