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Call Processing
When this capability is used on an H.323 tie trunk between Communication Manager switches,
the switch that receiving the H.245 tone message plays the required tone onto all the ports
receiving the audio stream.
Media stream for audio conferencing
When calls between IP endpoints are conferenced, the media streams must be routed through
the MedPro circuit pack.
Communication Manager allows the audio streams from different parties to come into different
Media Processor circuit packs. Each Media Processor sends its received signal to the TDM bus
in Pulse Code Modulation (PCM) format. All the other processors serving endpoints on the call
can then receive and sum the audio signals coming from all parties, and send the resultant
composite audio stream to the IP parties that it supports.
Figure 38: MedPro support of a three-party audio conference
on page 96 provides an example
to show how the MedPro circuit pack is configured for a three-party H.323 audio conference
using G.729. This conference is conventional in that it uses TDM bus timeslots to allow each
party to listen to all of the other parties. However, a more efficient form of conferencing is
possible when all the parties are IP endpoints, where the audio streams are multiplexed directly
on the Media Processor circuit pack, and no TDM timeslots are used. To establish the
configuration shown in
Figure 38: MedPro support of a three-party audio
conference, the DSP
resources on the MedPro are allocated as needed to audio conferencing. Communication
Manager balances the available media processing resources, effectively sharing load among
multiple MedPros.
Issue 3.4.1 June 2005
95
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