Collaboration Tools | Cisco TelePresence


Two common tools found in most conference rooms today are speaker phones and projectors. Most of today’s meetings consist of one or more individuals sharing documents with a group of people, often located in multiple locations. Using a web/audio conferencing tool such as WebEx allows users to simultaneously share documents and bridge audio between multiple sites, while using a projector to locally display content for in-room participants.
The Cisco TelePresence codec provides these features, allowing non-TelePresence users to participate, through audio only, in a TelePresence meeting and share documents with all meeting participants.

Auto Collaborate is a feature that allows any user in a TelePresence room to easily share any application on a laptop PC or an item from an in-room document camera. As with any in-room projector, a user simply connects a laptop to the VGA cable on the TelePresence table to start sharing. With an optional ceiling mounted or desktop document camera, users also have the option of sharing additional items such as documents, fabric samples, and so on with TelePresence participants. Users simply select the document camera softkey on the 7975 Series IP Phone and use the simple touch-screen phone interface to power on and control the document camera. Users don’t need to worry about granting control for sharing from one PC to another or a document camera. The last device to become active is the device that displays in all TelePresence rooms.

The VGA cable and document camera in the TelePresence room connect directly to the codec that automatically displays the image locally, using the system projector, while encoding the image and sending it to all TelePresence systems in the meeting. Application data is compressed using H.264 at 5 frames per second (fps), which is sufficient for sharing slides or items from a document camera but, in most cases, is not sufficient for full-motion video. If full-motion video is a requirement, a high-speed presentation codec can be added to the system providing 30fps for document and video sharing.

Most TelePresence meetings have attendees who don’t have access to a TelePresence room. TelePresence meetings can easily connect to a web/audio conferencing application such as WebEx or Meeting Place to accommodate non-TelePresence participants.

When the TelePresence meeting is in progress, one TelePresence room connects to the audio bridge, essentially adding the audio bridge to the TelePresence meeting, using the audio add-in feature. At the same time, the presenters in the TelePresence rooms join the web conference, allowing shared content to be viewed by all TelePresence and audio/web participants.

After the TelePresence meeting is connected to the audio/web conference, non-TelePresence participants can participate in the meeting using audio and view or even present, shared content throughout the meeting. The overall experience is similar to today’s meetings where a group of individuals meet in a conference room, dial into an audio bridge using a speaker phone, use a projector to locally display content, and share the local content with remote participants using web conferencing.

Audio add-in is a feature allowing audio-only participants to participate in a TelePresence meeting. From any TelePresence room a user simply selects the conference softkey on the 7975 Series IP Phone and dials the number of the audio participant or audio conferencing bridge. The audio add-in participants are connected through the initiating Telepresence system where audio is decoded, mixed, and played out all system speakers. The audio is then re-encoded in AAC-LD and sent to all Cisco TelePresence rooms in the same meeting.

Audio and Video Multiplexing

Each Cisco TelePresence system connects to the network using a single 100/1000 Ethernet connection. All TelePresence systems support multiple audio and video channels, allowing support for system video, audio, and shared data. Single-screen TelePresence systems support two audio channels and two video channels, whereas three screen TelePresence systems support four audio and four video channels. RTP multiplexing minimizes the number of video and audio connections across the network, providing a single video and single audio connection between any two Cisco TelePresence systems.

Audio Resolution and Compression Formats


The Cisco TelePresence system codec uses advanced microphone, speaker, and audio encoding technologies to preserve the quality and directionality of the audio so that it appears to emanate from the location of the person speaking at the same volume as it would if that person were actually sitting across the table from you.
The quality of the audio enjoyed by the meeting participants is a function of three variables:
  • Frequency spectrum captured by the microphones: The Cisco TelePresence microphones are designed to capture a 48-kHz spectrum of audio frequencies. The Cisco TelePresence speakers are designed to reproduce that same rich frequency spectrum.
  • Spatiality (that is, directionality) of the audio: To preserve the spatiality (that is, directional perception) of the audio, for larger Cisco TelePresence systems, individual microphones are placed at specific locations on the virtual table, along with speakers located under each display.
  • Degree of compression applied to the original audio signal: Inside the Cisco TelePresence Codec an onboard array of DSPs encode the audio signal from the microphones into RTP packets using the Advanced Audio Coding-Low Delay (AAC-LD) encoding and compression standard. The resulting bandwidth required to transport the audio signals between the systems is 64kbps per microphone. Therefore, a CTS-3X00 requires 192kbps of audio bandwidth, whereas the CTS-1000 or CTS-500 requires 64kbps of audio bandwidth.

Video Resolution and Compression Formats

The Cisco TelePresence 65-inch displays and cameras natively support 1080p and 720p resolutions and use digital media interfaces to connect to the codecs. This ensures the integrity of the video signal from end to end, eliminating the need for any digital and analog conversion.


Inside the Cisco TelePresence codec, an onboard array of Digital Signal Processors (DSP) encode the digital video signal from the cameras into Real-Time Transport Protocol (RTP) packets using the H.264 encoding and compression standard.

The quality of the video enjoyed by the meeting participants is a function of three variables:
  • Resolution (the number of pixels within an image)
  • Frame rate (how often pixels are redrawn on the display)
  • Degree of compression applied to the original video signal

Video Resolution

The 1080p resolution provides the highest quality video image currently available on the market, supplying a resolution of 1920 x 1080 and 2,074,000 pixels per frame. The 720p resolution provides a resolution of 1280 x 720 and 922,000 pixels per frame. Compared with today’s DVD standard video with a resolution of 720 x 480 and 346,000 pixels per frame, you can see the dramatic increase in resolution and pixel count. Figure 1 illustrates the difference between these three resolutions.

 
Figure 1: Video resolution


Frame Rate

The frame rate of the displayed video directly corresponds to how motion within the video is perceived by the participants. To maintain excellent motion handling, the Cisco TelePresence system encodes and displays video at 30 frames per second (30fps) at all times. In addition, the cameras and displays use progressive-scan technology to refresh the pixels within the video signal faster than with traditional television and video conferencing equipment that use an interlaced refresh format.
Compression
Note that 1080p video uncompressed is delivered at approximately 1.5Gbps. The Cisco TelePresence codecs must take this native video received from the cameras and compress it to a more feasible amount of bandwidth in as little time as possible. As mentioned previously, the codec achieves this by using an array of Digital Signal Processors (DSP) to compress the original 1.5-Gbps video from each camera down to under 4Mbps (per camera), representing a compression ratio of over 99 percent, which is done in under 90ms. The customer is provided with some amount of control over how much compression is applied. However, For each of the two resolution formats supported (1080p and 720p), the Cisco TelePresence codec supports three quality levels. Each quality level is really a function of the degree of compression applied with each quality level requiring a different amount bandwidth. For simplicity, these three levels are referred to as good, better, and best. The best quality level has the least amount of compression applied and, therefore, requires the most bandwidth, while the good quality level has the most amount of compression applied and requires the least amount of bandwidth.

Providing two resolutions and three quality levels within each resolution provides flexibility when deploying Cisco TelePresence. More importantly, it allows the Cisco TelePresence codec to automatically adapt to adverse network conditions by lowering the quality level and resolution to deal with packet loss.

Considering the three variables of resolution, frame rate, and the degree of compression applied, Table 1 illustrates the different quality settings supported by the Cisco TelePresence codec and the requisite bandwidth required for each quality setting.

Table 1: Resolution, Quality, and Bandwidth 
Resolution
1080p
720p
Quality Level
Best
Better
Good
Best
Better
Good
Frame Rate
30
30
30
30
30
30
Bandwidth
4Mbps
3.5Mbps
3Mbps
2.25Mbps
1.5Mbps
1Mbps

These bandwidth values apply per camera. Therefore, a CTS-3000 or CTS-3200 that has three cameras and three displays, running at 1080p resolution at the best quality level, requires 12Mbps of video bandwidth, whereas a CTS-1000 or CTS-500 requires 4Mbps of video bandwidth.