Current Publication | x

The Polycom RealPresence DMA System’s Primary Functions

The Polycom RealPresence DMA system provides the following primary functions:

Conference Manager

Call Server

RealPresence® Platform API

SVC Conferencing Support

Conference Manager

The Polycom RealPresence DMA system’s Conference Manager facilitates multipoint video conferencing. A multipoint video conference is one in which multiple endpoints are connected, with all participants able to see and hear each other. The endpoints connect to a media server (Multipoint Control Unit, or MCU), which processes the audio and video from each and sends the conference audio and video streams back to them.

Traditionally, such multipoint conferences had to be scheduled in advance, reserving ports on a specific MCU, in order to ensure the availability of resources. Conference Manager makes this unnecessary.

Conference Manager uses advanced routing policies to distribute voice and video calls among multiple MCUs, creating a single virtual resource pool. This greatly simplifies multipoint video conferencing resource management and uses MCU resources more efficiently.

The Polycom RealPresence DMA system integrates with your Microsoft® Active Directory®, automating the task of provisioning users with virtual meeting rooms (VMRs), which are available for use at any time for multipoint video conferencing. Combined with its advanced resource management, this makes reservationless (ad hoc) video conferencing on a large scale feasible and efficient, reducing or eliminating the need for conference scheduling.

The Polycom RealPresence DMA system’s ability to handle multiple MCUs as a single resource pool makes multipoint conferencing services highly scalable. You can add MCUs on the fly without impacting end users and without requiring re-provisioning. The RealPresence DMA system can span a conference across two or more MCUs (called cascading), enabling the conference to contain more participants than any single MCU can accommodate.

The Conference Manager continually monitors the resources used and available on each MCU and intelligently distributes conferences among them. If an MCU fails, loses its connection to the system, or is taken out of service, the Polycom RealPresence DMA system distributes new conferences to the remaining MCUs. Every conference on the failed MCU is restarted on another MCU (provided there is space available). The consequences for existing calls in those conferences depend on whether they’re H.323 or SIP:

H.323 participants are not automatically reconnected to the conference. In order to rejoin the conference, dial-in participants simply need to redial the same number they used for their initial dial-in. Dial-out participants will need to be dialed out to again; the RealPresence DMA system doesn’t automatically redial out to them.

SIP participants are automatically reconnected to the conference on the new MCU. This includes both dial-in and dial-out SIP participants. No new dial-out is needed because the RealPresence DMA system maintains the SIP call leg to the participant and only has to re-establish the SIP call leg from the RealPresence DMA system to the MCU.

Call Server

The Polycom RealPresence DMA system’s Call Server provides the following functionality:

H.323 gatekeeper

SIP registrar and proxy server

H.323 <—> SIP transition gateway

Dial plan and prefix services

Device authentication

Bandwidth management

RealPresence® Platform API

The Polycom RealPresence DMA system optionally allows an API client application, developed by you or a third party, to access the Polycom RealPresence® Platform Application Programming Interface (API). The API provides programmatic access to the Polycom RealPresence DMA system for the following:


Conference control and monitoring

Call control and dial-out

Billing and usage data retrieval

Resource availability queries

The API uses XML or JSON encoding over HTTPS transport and adheres to a Representational State Transfer (REST) architecture.


Note: The API communicates asynchronously. Clients subscribing to event notifications via the API must be prepared to receive notifications out of order.


A Polycom RealPresence Resource Manager system can integrate with the RealPresence DMA system via the API. The API provides the full programmatic access to the RealPresence DMA system described above and enables users of the RealPresence Resource Manager scheduling interface to:

Schedule conferences using the RealPresence DMA system’s MCU resources.

Set up Anytime conferences. Anytime conferences are referred to as preset dial-out conferences in the RealPresence DMA system.

SVC Conferencing Support

The Polycom RealPresence DMA system supports the Annex G extension of the H.264 standard, known as H.264 Scalable Video Coding (SVC), for both point-to-point and multipoint (VMR) calls.

SVC is sometimes referred to as layered media because the video streams consist of a base layer that encodes the lowest available quality representation plus one or more enhancement layers that each provide an additional quality improvement. SVC supports three dimensions of scalability: temporal (frames per second), spatial (resolution and aspect ratio), and quality (signal-to-noise ratio).

The video stream to a device can be tailored to fit the bandwidth available and device capabilities by adjusting the number of enhancement layers sent to the device.

For multipoint conferencing, the MCU doesn't have to do processing-intensive mixing and transcoding to optimize the experience for each device. Instead, it simply passes the video stream from each device to each device, including the enhancement layers that provide the best quality the device can support.

Polycom’s SVC solution focuses on the temporal and spatial dimensions. It offers a number of advantages over standard AVC conferencing, including:

Improved video quality at lower bandwidths

Improved audio and video error resiliency (good audio quality with more than 50% packet loss, good video quality with more than 25% packet loss)

Lower end-to-end latency (typically less than half that of AVC)

More efficient use of bandwidth

Lower infrastructure cost and operational expenses

Easier to provision, control, and monitor

Better security (end-to-end encryption)

Polycom’s SVC solution is supported by the Polycom RealPresence Platform and Environments, including the latest generation of Polycom MCUs and RealPresence room, personal, desktop, and mobile endpoints. Existing RMX MCUs with MPMx cards can be made SVC-capable with a software upgrade, and doing so triples their HD multipoint conferencing capacity.

RealPresence Collaboration Server 800s MCUs support mixed-mode (SVC+AVC) conferences. Both SVC and AVC endpoints can join the conference, and each gets the appropriate experience: SVC endpoints get SVC mode and get a video stream for each AVC participant; AVC endpoints get a single Continuous Presence (CP) video stream of the participants (both AVC and SVC) supplied by the MCU.

When the Polycom RealPresence DMA system selects an MCU that doesn’t support SVC for a conference configured for mixed mode, it starts the conference as an AVC-only conference (all SVC-capable endpoints also support AVC). But if the MCU supports SVC but not mixed mode (RMX 7.8), the conference fails to start.

Refer to your RealPresence Collaboration Server or RMX documentation for important information about the MCU’s implementation of SVC conferencing and its configuration, limitations, and constraints.

Related Topics

Machine Translation

You are cautioned that the translation of this document is generated by a machine; therefore, the translated document may have errors and be inconsistent with the original English language version of the document.

The English language version of this document shall be considered the governing document related to the Polycom product.

If there is any contradiction between the English language version of the document and the translated version of the document, the English language version of the document shall take precedence.

The translation is provided for your convenience only. Neither Google nor Polycom shall be responsible for translated content or for the performance of the translation tool. If you require further assistance on non-translation issues, please contact Polycom support.

Translated documents are not available in PDF format.