A Picture Is Worth a Thousand Words: Adding Video to Voice Calls

Cisco introduced video call support in version 4.0 of its CallManager software. Examples of video-capable Cisco IP Phones include the Cisco 7940G, 7960G, 7970G, and 7971G-GE IP Phones. However, Cisco continually introduces new IP phones and features. So, please check Cisco.com for the latest listing of video-capable phones.

The LCD on a Cisco IP Phone doesn't display the video in a video call. Rather, video appears on a PC attached to the IP phone, using the Cisco VT Advantage product, as shown in Figures 4-26 and 4-27.

Figure 4-26. Cisco VT Advantage Connection

Figure 4-27. Cisco VT Advantage Application

The CCM communicates with video-capable Cisco IP Phones via SCCP, and if those IP phones attach to a PC running VT Advantage software, the IP phones can report their video capabilities back to the CCM using SCCP. If both endpoints (that is, the IP phones on each end of a conversation) support video calls, the endpoints can set up a video channel between themselves.

The Cisco VT Advantage product includes software and a camera, as shown in Figure 4-28. The camera connects to a USB port on a PC. The VT Advantage software installs on the PC connected to the camera, and that PC connects into the Ethernet switch port on an IP phone.

Figure 4-28. Cisco VT Advantage Camera

Adding video to a call requires callers to rethink their behavior during a call. I admit it. I've talked with people on the phone, and while my voice sounded calm and friendly, the expression on my face told a different story, my rolling eyes indicating my impatience with the other party. Video calls require a bit more decorum.

Consider the mute function on an IP phone. When you're in an audio-only call and you press the mute button, the other party stops hearing you, allowing you to have a private conversation in your office. Consider a situation where you're conducting an important business video call, and you press the mute button on your IP phone. If you want audio privacy, chances are, you want video privacy too. Fortunately, the Cisco VT Advantage product pauses the video of a video call when you press the mute button on an IP phone. Also, you can optionally configure the VT Advantage software to a receive-only mode, where you see video from the other party, but the other party doesn't see you.

Besides two-party video calls, the Cisco product line features multipoint control units (MCUs), which mix audio and video streams together to support video conference calls. Examples of the Cisco video MCUs include the IP/VC 3511 (supporting 15 simultaneous video conference participants), and the IP/VC 3540 (supporting up to 100 simultaneous conference participants), as shown in Figure 4-29.

Figure 4-29. Cisco IP/VC 3540 Multipoint Control Unit

The IP/VC 3540 MCU mixes the audio and video from conference participants. Cisco supports two options for viewing conference participants:

  • Voice activated The voice activated display mode shows the video of the conference participant currently speaking.

  • Continuous presence The continuous presence display mode continually shows up to four participants on a screen. However, if a conference contains more than four participants, off-screen participants (that is, participants that are not currently one of the four displayed participants) are displayed if they begin to speak.

Consider a situation where Phone A is video capable, and Phone A calls Phone B, which is not video capable. Because Phone B lacks video support, Phone A only sends audio to Phone B. However, let's say Phone B transfers the call to Phone C, which is video capable. Because both devices in the call (that is, Phone A and Phone C) now support video, the call, which once only used audio, starts to transmit both audio and video between the endpoints.

Because a video call requires more bandwidth than an audio-only call, during peak WAN usage, enough bandwidth might be available for an audio call but not for a video call. CCM administrators can configure Cisco IP Phones to retry a call as an audio-only call if a video call attempt fails.


Cisco CallManager also supports third-party H.323 video clients, allowing existing H.323 systems to leverage the power of Cisco CallManager features.

Voice over IP First-Step
Voice over IP First-Step
ISBN: 1587201569
EAN: 2147483647
Year: 2005
Pages: 138
Authors: Kevin Wallace

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