How to Design a Telepresence Room
With travel costs rising and companies growing ever more global, it isn't always possible for colleagues to meet in person. A well designed telepresence room can only add to the effect of being where you aren't.
Factor 3: Audio Bandwidth
When designing the audio side of a telepresence room, don't overlook system bandwidth. With today's modern microphones, mixing equipment, signal processing, and amplification, it's often not even thought of, but that would be a mistake.
Remember that the audio bandwidth of the signal sent to the far side often does not exceed 7 kHz. Don't use microphones with a bandwidth equal to or less than the bandwidth of the signal link; the system will sound worse than it would if you used microphones typically found in either recording or live sound reinforcement applications.
Factor 4: Lighting
Obviously, perhaps the most important part of telepresence room design has to do with the visual experience: the cameras, display size and resolution, and lighting.
Room lighting for telepresence systems is no different than what is recommended for a typical video teleconferencing system. The Illuminating Engineering Society of North America (www.iesna.org) offers handbooks on the subject and Pro AV editorial advisor Tim Cape, CTS-D, has written on the topic before. (Visit www.proavmagazine.com and search on "lighting for videoconferencing.") In a nutshell, you're balancing comfortable lighting for local participants with proper lighting to ensure a camera, codec, and display system can reproduce an optimal experience.
Factor 5: Camera Positioning
From there, visual design is about recreating that in-person experience. People prefer to speak eye-to-eye and face-to-face with one another. Think of what it's like when someone doesn't look directly at you when they respond to a question or a request.
The face-to-face dynamic can be replicated through the proper placement of cameras and displays. Ideally, the center line of a camera's lens should be at seated ear height (+44 inches above finished floor, or AFF) or slightly above (up to 48 inches AFF). Note: In telepresence it isn't necessary to provide a camera with pan/tilt/zoom capabilities because the room and where people sit are meant to be tightly controlled, unlike in a typical VTC environment.
Lens focal length should be determined by the distance the two (or more) parties would be seated from each other in a real meeting. For instance, if the client would meet an in-person colleague across a 5-foot-wide table, the focal distance of the lens should take into account the virtual size of the person you're meeting with across the void and the number of people each camera will see.
So where is the camera placed relative to the display? As DVE's* Machtig points out, this is the determining factor in the success of an immersive telepresence environment because so much of non-verbal communications is expressed with our eyes.
Again, if we were building the ideal room, we would align the center axis of the camera with the center axis of the displayed image, so you had the illusion you were talking directly to the people at the far site. This would place the camera behind a piece of two-way glass while the display would be mounted to reflect its image onto the glass.
Most solution providers choose not to implement this model, however, so compromises are made in this vital area. Choices include placing the camera above the display (which can be unnatural for the viewer as they look down on the top of your head, especially in a shorter throw application); or placing the camera below the display, which forces the participants to look up; or placing the camera between displays.
Although alignment with both axes of the display is ideal, I would opt for placing the camera either between the displays (first choice) or above the display. But reasonable designers can disagree. The more your client is willing to spend on high-end, complete VTC solutions, the more likely you are to find a system that fits the camera in small, unobtrusive positions, like between blended, bezel-free displays, or built into the system just above the screen.
This story was edited to correct the name of Machtig's company, Digital Video Enterprises (DVE)
Factor 6: Display Positioning
Determining the image size you need requires you to follow the usual formulae that tie image size, target distance, and focal length together. Most imaging chips are either 1/3- or 1/4-inch CCD devices, with either 720p or 1080p resolutions.
The displays you choose should be large enough to accompany life-size images of remote meeting participants–as many as two per display–and enough of their surroundings to underscore the in-person experience.
Credit: Brad Grimes
This then drives the size of the display you want to use. Since participants are meeting across a virtual table, you want them to be able to see a portion of that table and up to a reasonable height above the table. Because seated ear height is +44 inches AFF (on average), add an allowance of 10 to 12 inches (including forehead) to ensure you don't give someone an unwanted crew cut on the monitor. This puts the top of the image at +56 inches AFF.
Considering the surface of a conference table is normally at +29 inches AFF, you'd be looking at an image height of roughly 27 inches. If you allowed for including some of the conference table (ideal for telepresence but usually only if the local and remote rooms are well controlled and include the same conference table), this would place the bottom of the image at +26 inches AFF, requiring an image size of roughly 31 inches.
At a minimum, you should choose a 54- to 60-inch diagonal display device. With this size display, you may be able to fit two people onto one display. (It seems counterintuitive, but the wider your virtual conference table, the smaller the display needs to be.) High-end systems often come with larger displays (see "Telepresence in a Box, page 32").
Factor 7: The Displays
Finally, the resolution of the display should match the resolution of the cameras being used to capture images, or the minimum resolution of the codecs being used. In most cases, this means a 1280x720 display, because the minimum HD resolution used in most telepresence systems is 720p. At the image sizes discussed above, this resolution will actually be higher (typically 1365x765). This is the lowest common denominator for most manufacturers, and typically acceptable by most users. The larger the displays you choose to create the immersive experience, the more likely you are to need higher definition displays.
Clearly, there are many factors that go into telepresence design that are beyond room and system setup, such as bandwidth (a 1080p telepresence meeting could consume up to 18 Mbps) and frame rates. After you have a handle on the room design, these technology factors will require analysis of the client's application requirements and expectations.
Because telepresence can vary in scope, and because so many acoustical, design, human, and technology factors can affect the total experience, there are obviously compromises along the way that might result in a less than ideal telepresence experience for the viewer. We already see some of these compromises introduced by manufacturers seeking to find price points for their pre-integrated equipment that can meet customers' various needs and budgets.
But if you as an AV pro begin with the end result in mind–marrying design, technology, and physics to make the users feel like they're face to face with distant colleagues–then you've laid the proper groundwork and likely optimized the experience regardless of the scope and complexity of the system itself. Even if the client doesn't opt for a quarter-million-dollar system, they can still enjoy an in-person discussion with people on the other side of the table–or the world.
Pro AV contributing editor Thom Mullins is a senior consultant with BRC Acoustics & Technology Consulting in Seattle.