Prosody's media processing
resource capabilities provide real-time, multi-party conferencing on Aculab's high performance CT cards. Prosody offers a highly integrated conferencing service, lowering overall system costs, reducing the development cycle and time to market. Coupled with Aculab's unparalleled digital network access support and single, generic API, Prosody enables fast, global deployment of conferencing solutions.

Conferencing applications
Conferencing system features and capacities vary depending on the market segments they target. Small to medium enterprises (SMEs) may look to enhance the built-in conference call functions of their phone system, while larger companies may require a stand-alone solution for intra-company conferencing. Carriers and service bureaus may look to provide large scale conference facilities as a business offering. Some example applications include premium rate chat lines, intra-company worldwide training, distance learning and corporate referendums or voting.

Prosody's conferencing allows developers to create flexible applications to suit any of the above market segments. By eliminating the need for dedicated, specialised conferencing hardware, Prosody presents a cost-effective solution for delivering conferencing with powerful features and high quality audio. Prosody is available in several configuration variants on standards based PCI and CompactPCI (cPCI) cards.

Flexible conferencing options
Prosody's conferencing capabilities can provide a framework for various conferencing scenarios as in the diagram below. A low-level (matrix) and a high-level API are provided as conferencing extensions to Aculab's generic API. The high-level API library provides a simple interface that allows conferences to be constructed and manipulated using just a few API calls. Using the matrix conferencing API it is possible to link multiple DSP modules together to create very large conferences of up to 248 participants on each card.


Two-party conferencing
Two-party conferencing is typically used when building call logging and recording applications based on Aculab's Passive monitor card. Two-party conferencing mixes both sides of a conversation into a single recording.

Large conferences
Prosody's conferencing has a comprehensive range of features, including support of large conferences and complete control of speakers' and listeners' participation within a conference.

Developers can create a large conference using a single DSP (maximum 64 participants per DSP) or several independent conferences using one or more DSPs. In addition it is possible to create very large conferences by connecting DSPs together using one or more cards. There are three approaches to building larger conferences when using Prosody. With these alternative methods the size of the conference is determined in different ways and developers should choose the method that is suited to their needs.

Functions within matrix conferencing

  • Volume control can be enabled in one of two ways; standard conferencing with volume control of the output level, and conferencing with individual volume control on a participant's input signal. The latter is useful when implementing multiple conference loops, where a speaker may be in several loops, in order to control individual speaker volume.

  • Automatic gain control (AGC) can be enabled for conferences to automatically adjust the volume and maintain it at an appropriate level. If no speaker is detected the AGC function will suppress a conference input channel in order to avoid passing through the background noise.

  • DTMF clamping (tone clamping) on an input means that if the participant's phone generates a tone, the DTMF signal will not interfere with the conference. This is useful, to minimise annoyance to other participants and prevent unwanted detection of echoed tones.

  • Echo cancellation / suppression can be used in a conference to ensure an acceptable quality listening experience for all participants. Prosody's echo cancellation options suppress echoes within a conference, with echo cancellation coverage over 25ms of echo path delay.

  • Active speaker detection can be used to track individual speakers by noting when speech is on the line. The conference is analysed to see which participants are speaking at the time and the API allows an application to track this, with control over the sensitivity of speaker levels. This is useful for transcription of minutes and recording 'who made which statements'.

  • Recording the conversation between all participants is a common requirement in conferencing applications. Recording allows carriers or service bureaus to generate additional revenue through offering extra services like supplying a recording of the call, or a full transcription.

  • Prompts may be played to either individuals or all participants to relay information for training or voting, for example.

  • Conference monitoring allows a moderator to hear and/or speak to all or selected conference participants. This feature enables the involvement of a conferencing 'coach' - a participant who can speak to an individual without being heard by other users. The targeted participant will still be able to hear and take part in the conference. Similarly, the coach can remove a user's ability to communicate with the rest of the group, but still be able to listen.


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