Prosody X PCI Express R1 Card – Installation Guide
Media Rich DSPs
The card has up to 2 media DSPs fitted which allow the processing of and conversion
between IP and TDM based media streams.
1.3
Call control
The call control interface is at a low level (in signalling terms), and provides maximum
information and control over the various stages of call progress, (set-up, acceptance,
clearing, etc). This interface is accessed via a device driver that has been prepared
for the operating system in use.
The call processor checks each outgoing message provided by the application
program for syntax, validity of content and context. If errors are found, the call can be
automatically cleared. In these instances the software can form an effective barrier
between the application program and the telephone network, protecting the network
from invalid call signalling.
Several elements of call signalling related information are available to the application
program, although in some cases this depends upon provision of call specific
information by the Public Switched Telephone or Ethernet networks. One such
information element is the number used by the caller on calling into the card, (the DDI
number). This is only available when the service obtained from the PSTN is of the
appropriate type. Another information element which may be available, is Calling Line
Identity (CLI). On incoming calls, CLI makes the telephone number of the calling party
available to the application program.
Full details on the control of calls using the Prosody X PCI Express card are available
in a separate publication
‘Aculab Call Control API Guide’,
which can be
downloaded from
the support area of
the Aculab company web site at
www.aculab.com
1.4
Media processing functions
The Prosody X PCI Express card is designed for processing digitised speech data,
with support for recording/playback, echo cancellation, conferencing, DTMF, and call
progress tones and more. This functionality is available when one or more media
DSPs are present.
Further details are available in the Aculab TiNG API guides and Application Notes.
Speech or data is transferred in either direction between any of the following:
•
The host storage medium
•
Any of the channels on the H.100 CT expansion bus or the E1/T1 trunk
connections
•
Any RTP endpoints on the Ethernet connection in use
The media processing DSPs on the Prosody X PCI Express card can provide various
processing functions on the data including:
1.4.1 Playback and recording of speech data
•
Compression and decompression between the H.100 64kb/s speech data and
the host computer hard drive. Please consult www.aculab.com for a list of
supported algorithms.
•
Pitch invariant fast and slow replay (50 to 200%) at all data rates
•
Trimmed recording to eliminate periods of silence at all data rates
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