Polycom Video Communications
- 1. Polycom Video Communications Advanced Audio Technology for Video Conferencing Author: Peter L. Chu September 2004 Connect. Any Way You Want.
- 2. If you ask frequent users of video conferencing Why Siren 14 Audio is Important technology what they consider to be the number Speech information is usually contained in the one product feature for providing a high quality 100-11,000 Hz range, so having frequencies video conferencing experience, their response above 11,000 Hz is not important except for will most likely be the requirement for excellent music. While a small minority of people can audio. High quality audio is far more important hear up to the limit of 20,000 Hz in audio to the perceived quality of a video conference frequency, the large majority of people cannot as dialogue, discussion and decision making are hear the difference between 14,000 Hz and usually the most important elements between 20,000 Hz high frequency limits for even the meeting participants. most demanding music material. The Siren14 codec in the iPower 9000 and VSX 3000, VSX With an undisputed leadership role in the audio 7000 and VSX 8000 provides audio capability conferencing segment, Polycom also takes the up to 14,000 Hz, allowing for transparent leadership role with our outstanding audio reproduction of both speech and music. quality in video conferencing systems. It is Polycom's goal to create and provide video con- The Siren 14 algorithm suite, developed and ferencing solutions that deliver the highest patented by Polycom is designed to provide a quality audio capabilities for any environment. scalable wideband audio solution that will obviate With Siren™ 14 and now patent pending any reason to use narrow band (3.4 kHz) audio Polycom StereoSurround™ audio technology, coding. When combined with Polycom patented Polycom once again raises the bar for quality audio echo cancellation, the suite provides an audio standards and delivers true performance environment that allows both the local and to our customers. remote speaker to engage in conversation simultaneously, without cutting each other out. Polycom's leading advantage: Siren 14 Siren 14 operates at 14 kHz audio at bit rates Polycom's Siren 14 technology brings 14 kHz between 24 and 48 kbps, the usual bandwidth audio fidelity for the most natural conversation. allocated to audio transmission in a video With twice the fidelity of other vendors, and conference. Polycom's unique Siren 14 Super four times the fidelity of a telephone call, wide band audio capabilities provides incredible Polycom is the only company in the industry to audio quality approaching compact disk and offer such "super-wideband" audio capabilities MP3 quality, while maintaining a modest network for video conferences. bandwidth requirement. In comparison to other audio algorithms, such as MPEG 3 and MPEG 4 With 14 kHz audio in a video conference call, at lower bit rate transmissions, Siren 14 actually participants can better hear and understand delivers a smoother and more superior sound. each other, while eliminating the fatigue often associated with longer duration calls under inadequate audio quality. 2
- 3. Polycom's Digital Tabletop Microphone: A natural companion for Siren14 Most video conference systems use simple directional microphones. Typically these micro- phones have a (+/- ) 45 degree pickup pattern as measured from the axis pointing from the front of the microphone. The disadvantage of this type of microphone is that participants who are sitting away from the pickup pattern cannot be heard as well as those sitting closest to the microphone. Polycom digital tabletop micro- phones deploy technology that allows for voice pickup in a 360 degree radius covering distances up to 10 feet away from the microphones. Polycom digital tabletop microphones also use background noise suppression functions which eliminate unwanted background noise such as that generated by laptop or projector fans and vents. The benefit of automatic noise suppression creates a virtually noise-free communication for most meeting environments. Diagram 1: Area pickup of Polycom Digital Tabletop microphone compared to other microphones. By using Polycom's digital tabletop microphone merely adequate audio reproduction for a low The Total Polycom Audio Solution technology combined with the Siren 14 audio price. As a result, these television speakers often With all of these great audio technologies, it is algorithm, conference attendees can sit anywhere sound similar to a portable stereo system. easy to see why Polycom's audio is the best in in the room without having to worry whether the industry and why Polycom continues to be their voices are being heard at the remote sites. Polycom offers custom high fidelity audio the market leader in video conferencing solutions. An example of this capability is exemplified speaker systems to provide the highest quality within the tabletop microphone shipped with speech reproduction for video conferencing. Setting a new standard: Polycom Stereo the VSX™ 7000 product series. The VSX 7000 The VSX 7000 is the world's only set-top video Surround tabletop microphone deploys a three element conferencing system that includes an integrated Consumers are used to enjoying stereo audio microphone array that forms a narrow beam that speaker and companion subwoofer to provide when listening to music, watching DVD movies, automatically points to the person speaking. The near CD-quality audio in any setting. The Polycom or even experiencing impressive multi-channel narrow beam eliminates noise and reverberations Executive Collection offers a 270 Watt speaker audio at movie theatres. Stereo makes the overall from other directions.. When several microphones subsystem with each Executive Collection con- multimedia experience more realistic and less are linked together, the microphone nearest the figuration; ideal systems for this configuration fatiguing, providing us the required spatial cues person speaking is automatically and seamlessly include the Polycom iPower™ 9000, VS4000™ to separate out different sounds. On a video chosen while noise from the remaining and VSX 8000. Polycom also provides an auxil- screen, when someone on the left hand side of microphones is eliminated. iary Speaker Kit, ideal for adding Polycom the screen talks, we expect that sound to come StereoSurround capabilities to the VSX 7000 or out the left side, and stereo allows this to happen. Audio Reproduction from Polycom VSX 8000. This Speaker Kit consists of a sub- In our everyday life, we are used to having Equally important to participants in a video woofer with 150 watts output power with two sounds come from all directions. In mono con- conference is sound fidelity of the speakers that 6-inch drivers with bass response down to 35 Hz ferencing, when every sound comes from a single produce the audio signals. Clear speech, after and dual speakers that include a 3/4" silk fabric point in space, it is very artificial and fatiguing. all, is noted as one of the the most important dome tweeter combined with two 3 1/2" compos- elements of a video conference. Often, end users ite midrange drivers for superb sound reproduc- To make stereo audio conferencing a reality, rely on the quality of television speakers for video tion at frequency ranges of 100 Hz to 22 kHz. Polycom has developed breakthrough patent conference audio reproduction. These speakers, pending technology for the VSX 8000, however, are not well suited for reproducing VSX 7000, VSX 3000, and other products. The speech, the most commonly transmitted audio technology includes stereo echo cancellation, signal in video conferencing applications. Automatic Gain Control (AGC), noise suppres- Television speakers are usually designed to offer sion and audio compression technology. 3
- 4. Echo Cancellation: The Enabler for Polycom The Basis for Polycom StereoSurround Loudspeaker Placement for Group Video Systems StereoSurround A stereo version of Polycom's Siren14 codec has For the optimal realization of Polycom If stereo audio is so ubiquitous in the consumer been developed to give high quality 14 kHz StereoSurround, it is necessary to place the industry, why it is absent in the video confer- bandwidth stereo audio at lower bit rates than left and right loudspeakers in the correct encing industry? The problem has to do with MPEG 4, thereby allowing video to have more positions. The optimal angles for the left and right echo cancellation. Echo cancellation is required bits for sharper images. Polycom StereoSurround loudspeakers should be +/- 30 degrees with to eliminate the pickup of the loudspeaker by works at 48, 64, and 96 kilobits per second. respect to an average audience. To ensure prop- the microphone. Without echo cancellation, Polycom hopes that offering stereo audio capa- er placement of loudspeakers, go to users would hear feedback which would make bilities as part of the standard feature set on System/Diagnostics/Speaker Test. When the the conference very annoying. Conventional video conferencing system will popularize the left speaker icon is enabled, the tone should echo cancellers identify only one path between use of high-quality audio in video conferencing. come out of the left loudspeaker. Do the same the loudspeaker and the microphone. In stereo, In the international standards body for video test for the right loudspeaker. Loudspeaker place- there are a multiplicity of paths between the two conferencing, the ITU-T, Polycom is sponsoring ment for use with the VSX 7000 or VSX 8000 is loudspeakers and microphone, which confuses the adoption of Siren14 as a standard extension illustrated in the diagram below. the echo canceller. To solve this problem, many to the existing G.722.1, which is also a Polycom researchers have resorted to distorting the left developed codec. Another way to view proper speaker placement and right loudspeaker signals, which enables is that the distance between left and right loud- correct estimation of the multiple paths. Speaker and Microphone Positioning on the speakers on either side of the TV monitor should Unfortunately, this distortion can often be VSX 3000 equal the distance between the TV monitor and heard, especially for music. Since the VSX 3000 ships with two integrated the midpoint position of the audience. So, for speakers (left and right) and two integrated example, if the midpoint of the audience is 12 After a decade of research, Polycom has microphones (left and right), it is ready for feet away from the TV monitor, the left loud- developed patent pending stereo echo canceller Polycom StereoSurround right out of the box speaker should be 12 feet away from the right technology which doesn't distort the signal, yet without any additional hardware. Simply enable loudspeaker. Separating the loudspeakers by quickly identifies the multiple paths of the the stereo feature in the user interface and this amount allows the average listener to stereo loudspeakers and eliminates echo, begin making video calls. The difference will be perceive sound coming from left loudspeaker, allowing for full-duplex conversations. There is immediately noticeable! right loudspeaker, and points in-between the no "white noise" training sequence, as found in two loudspeakers. competitor's mono echo cancellers. Positioning of the loudspeakers and microphones is not critical. If microphones are moved, the stereo echo canceller quickly adapts to the new posi- tion within one or two words of speech. For the frequency range from 50 Hz to 14,000 Hz, the echo canceller adaptive filter length is 160 milliseconds which is adequate for even large rooms of 30 by 50 by 9 feet in dimension. The echo canceller works as well with stereo music as it does with speech. Other Polycom stereo acoustic signal processing: AGC and Noise Suppression Polycom's artifact-free stereo noise suppression is applied to the microphone signals to eliminate hiss and fan noise. The noise suppression adapts within several seconds to new noise sources which are introduced, like someone turning on a projector. Additionally, a voice- activated stereo AGC is included to automatically increase microphone gain for people who are further away from the microphone. Optimal placement of left and right loudspeakers for Polycom StereoSurround 4
- 5. Microphone Placement for Group Video Systems Stereo microphone pickup is accomplished in the VSX 7000 and VSX 8000 by utilizing two microphones. One microphone picks up all audio for the left audio channel while the other microphone picks up all audio for the right audio channel. Knowing which microphone is left and which is right can be determined by going to the VSX 7000 or VSX 8000 menu, Admin Settings/Audio/Stereo Settings. Lightly tap each microphone to identify their positioning by watching the Left and Right microphone meters in the UI. If necessary, swap the left and right microphones to correctly correspond to the meters. The left microphone's purpose is to pick up sound in the left half of the audience. As such, it should be placed in the center of the left half Optimal placement of left and right microphones for Polycom StereoSurround on a horizontal table. of the audience, towards the front, as people tend to speak facing the video display. For the right microphone, a similar situation applies. The diagrams to the right illustrate proper placement of the micrphones for both hoizontal and perpendicular orientation of the table rela- tive to the video display. The Polycom Office™ With integrated video, audio, data, and Web capabilities, The Polycom Office is the only solution that offers an easy way to connect, conference, and collaborate any way you want. Work faster, smarter, and better with The Polycom Office. Polycom, Inc. develops, manufactures and markets a full range of high-quality, easy-to-use and affordable voice and video communication endpoints, video management software, web collaboration software, multi-network gateways, and multi-point conferencing and network access solutions. Its fully integrated end-to-end solution, The Polycom Office, is supported by the Polycom accelerated communications architecture and enables business users to immediately realize the benefits of integrated video, voice data Optimal placement of left and right microphones for Polycom StereoSurround on a perpendicular table. and web collaboration over rapidly growing converged networks. 5
- 6. ©2004 Polycom, Inc. All rights reserved. Polycom and the Polycom logo design are registered trademarks and Siren, Polycom StereoSurround, VSX, iPower, VS4000 and the Polycom Office are trademarks of Polycom in the U.S. and various countries. All other trademarks are the property of their respective owners. Specifications subject to change without notice. Polycom Headquarters: 4750 Willow Road, Pleasanton, CA 94588 (T) 1.800.POLYCOM (765.9266) for North America only. For North America, Latin America and Caribbean (T) +1.925.924.6000, (F) +1.925.924.6100 www.polycom.com Polycom EMEA: 270 Bath Road, Slough, Berkshire SL1 4DX, (T) +44 (0)1753 723000, (F) +44 (0)1753 723010 Polycom Asia Pacific: Polycom Hong Kong Ltd., Rm 1101 MassMutual Tower, 38 Gloucester Road, Wanchai, Hong Kong, (T) +852.2861.3113, (F)+852.2866.8028 Rev 9/04