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Dialogic® Host Media Processing (HMP) Software
Dialogic® Device Management API Connection Types
An overview of when/how Dialogic® Device Management API calls dev_Connect and dev_PortConnect should be usedIntroduction: There are now several options for connecting audio and video media transports and endpoint devices. Dev_PortConnect() was introduced in the latest Dialogic® Multimedia Software for AdvancedTCA Release 1.1 and Dialogic® Host Media Processing Software Release 3.1LIN. In prior releases of each, dev_Connect() was introduced as a way of interconnecting IPML, MM, T.38 fax and CNF devices.
It may not be readily apparent when, and with which devices, connection methods should be used. This technote explains the intent of the different API calls, and gives guidelines for using both dev_Connect and dev_PortConnect.
Dev_Connect()
Dev_Connect() is widely used by most current IPML/MM application. By default it connects audio linear ports and video native ports. In this case, "linear" means audio in a straight PCM format. This can be thought of as the "lowest common denominator" from which other forms of compressed audio can be derived using a codec. So, audio transcoding is done with dev_Connect(), for example. Video "native" ports, however, mean that the video stream is available only in its native format - i.e. the one in which it was generated, so no transcoding can be done. Currently the format used is H.263.
A dev_Connect() connection can be either half or full duplex, depending on the needs of the application. The desired type of connection is specified as a paramter in the function call.
Use of dev_Connect() should be limited to connecting legacy timeslot-based devices:
- Existing video applications connecting a mutlimedia endpoint to an RTP streaming device (MM-IPML)
- 3G-324M applications connecting the 3G device to a DS0 timeslot (3G-DTI)
- Existing an audio conferencing device to a DS0 timeslot and voice device (CNF-DTI-DX)
- T.38 Fax device to an RTP streaming device (IPML, DX)
Dev_PortConnect
The API call was introduced to allow native audio connections in addition to native video. It is used to accomplish native play, record and hairpinning. Dev_PortConnect() should be used every time a "p-stream" (packet interface) is connected internally to a another p-stream. Devices that can be used are:
- 3G-342M connecting to IPML
- 3G-342M connecting to MM
- MM to IPML
- 3G-324M to a second 3G-324M for a hairpined connection
- IPML to a second IPML for a hairpined connection
DevPortConnect() allows granular control over which ports to connect, e.g., connect only audio or only video. And with multiple receive ports in its port list, a one-to-many connection can be done to broadcast to multiple devices. A transcoding flag is used to indicate if the connection is native, or if transcoding should be done. Currently (10/2007) video transcoding cannot be done, but the expectation is that it will soon be available.
Some amount of preparatory work needs to be done before dev_PortConnect can be called. Structs containing internal information on transmit and receive ports for all devices involved must be obtained from calls to dev_GetTransmitPortInfo() and dev_GetRecievePortInfo(). These asynchronous calls return information on their respective ports that must be saved and then used in the dev_PortConnect() call.
Connections made with dev_PortConnect() should be broken with dev_PortDisconnect().
Product List
The Device Management API is used on both Dialogic® HMP Software and Dialogic® Multimedia Platform for AdvancedTCA® .
Related Documentation
Dialogic® Device Management API Reference Manual
