CAF: Working With Call Legs

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== Call Leg Definition ==
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TelcoBridges Toolpack framework offers two API layers to manipulate call legs and audio mixers (conferences).
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The main mechanism through which the customer application controls the Toolpack system, is via the management of call legs. The application creates a call leg (or more than one for conferencing and bridging) at the beginning of call, then control it through a simple, protocol-agnostic API. When a call is terminated, the call leg can be destroyed.
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A call leg is respresented by an instance of the class CTBCMCLeg. It represents a  full-duplex media resource and/or its associated
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We recommend that developers use the CAF API layer, as it offers higher-level functionality which accelerate application development.
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signalling entity. Typical examples of call leg with signaling would be an SS7 ISUP call with its associated CIC (mapped to a TDM
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interface such as a T1 timeslot) or a SIP call with its associated Voip codec resource (attached to an IP/UDP endpoint). A media-only call leg would represent a standalone TDM endpoint (such as a T1 timeslot) or a VOIP endpoint (Voip codec resource attached to an IP/UDP endpoint). Section [[Customer_Application_Framework_:_Working_With_Call_Legs#Creating Call Legs | Creating Call Legs ]] will show how different types of leg can be created.
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The CTBCMCLeg class allows a programmer to easily act upon the call leg to influence the signaling portion (e.g. accept, answer,
 
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terminate, etc) and to use the media portion as well (e.g play prompts, record voice, play or collect digits and tones).
 
  
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Other member functions are available to retrieve (and change in some cases) the call leg attributes including the media
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==  CMC API layer ==
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profile (e.g. parameters to the media resource) or signaling information (e.g. protocol type, called and calling party
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numbers, etc). Joining/unjoining (connection/disconnection) of call legs is also a typical action handled by this class
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for ’gateway-type’ applications. It is important to note that this class is protocol-agnostic and can handle any type of
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supported call legs (e.g. SIP/Voip, ISDN, SS7, Media only, etc).
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The lower-level API is based on classes ''CTBCMCLeg'' and ''CTBCMCMixer''. These classes allow receiving leg or mixer events (answered, digit collected, terminating, etc.), and send requests to perform actions (answer, play, terminate, etc.).
  
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===== Caveats =====
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The following page explains how to work with CTBCMCLeg directly, for lower-level applications that don't want the convenience of the CAF Call framework
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* Do not confuse a ''call leg'' with a ''call''. A ''call leg'' represents one full-duplex link to a party while a ''call'' represents
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the agglomeration of multiple (two or more) call legs. For example, a ''bridge'' is a form of ''call'' that uses two ''call
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[[CAF:_Working_With_Cmc_Call_Legs|Working with CMC Call Legs]]
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leg''s.
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* Do not confuse the base class CTBCMCLeg with the class CTBCAFCallLeg. The later is an implementation class specialized to be used by
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== CAF API layer ==
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the ITBCAFCall interface when dealing with multiple legs. It is designed to represent a leg within a call. It
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cannot be instanciated as a standalone object without modifications to make it independent from the ITBCAFCall interface.
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* If the overall goal is to bridge two or more call legs together, then the programmer would be advised to use the
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CTBCAFCallFlow class for leg creation instead of creating call legs manually. This class already deals with the issues of handling multiple legs simultaneously.
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== Creating Call Legs ==
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A higher-level API uses the base classes ''CTBCMCLeg'' and ''CTBCMCMixer'', but adds the following functionalities:
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Creating a leg is always done through the definition of a ''call leg attribute''. The values entered in the ''call leg attribute'' will define the type of call leg created and it's parameters. The following sections describe several scenarios in which you build a ''call leg''. Instruction will be given on how to fill the leg attributes and how to use them to create the ''call leg''.
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- Simplification of call legs creations through single functions (''AddIncoming'', ''AddOutgoing'', ''CreateMixer'')
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- Centralizing reception of events from call legs and mixers in to a single "Call Flow" (''CTBCAFCallFlow''), which deals with inter-relations between legs and mixers.
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- Auto-destruction of call legs (''CTBCMCLeg'') and mixers (''CTBCMCMixer'') through usage of "smart" pointers.
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- Auto-destruction of the call flow (''CTBCAFCallFlow'') upon destruction of last leg/mixer.
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The following page explains how to work with CAF Call leg framework (CTBCAFCallLeg, CTBCAFCallFlow, CTBCAFCallBehavior, etc...)
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[[CAF:_Working_With_Caf_Call_Legs|Working with CAF Call Legs and behaviors]]
  
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TODO Present call flow for leg creation.
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The following page provides more details on call legs re-synchronization between toolpack_engine application and user "CAF" application:
  
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=== Leg Creation Scenario ===
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[[CAF:_Call_Legs_Resync|Re-synchronizing CAF call legs]]
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==== Creating a Standalone Outgoing Call ====
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==== Bridging an Incoming Call (manual method)====
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==== Bridging an Incoming Call (using CTBCAFCallFlow )====
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==== Creating a Media-only Leg ====
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=== Caveats ===
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* The call leg attribute is an object containing the call leg information (called/calling numbers, etc) that needs
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to be allocated by the caller (in this example the ’main’) and given to the call leg object. It will be freed
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automatically when the leg is destroyed.
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* The base class does not automatically free itself. This is why the member function OnCallTerminated() was
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overloaded to actually instruct the base class to start the freeing operation once the signaling call is done. In
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CMC User’s Guide
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another type of application, some steps could be required before the actual leg free is desired (such as logging,
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DB access, etc).
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* The ’delete’ operation on the call leg is eventually done by the object exposing the ’freeListener’ interface. This
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allows the application to centralize (if required) the ownership of objects to a single entity. This means that
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an object could also self-delete if it is given its own ’freeListener’ interface pointer. This all depends on the
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hierarchy of object owership the application designer wants to do.
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Latest revision as of 06:09, 19 October 2012

TelcoBridges Toolpack framework offers two API layers to manipulate call legs and audio mixers (conferences).

We recommend that developers use the CAF API layer, as it offers higher-level functionality which accelerate application development.


CMC API layer

The lower-level API is based on classes CTBCMCLeg and CTBCMCMixer. These classes allow receiving leg or mixer events (answered, digit collected, terminating, etc.), and send requests to perform actions (answer, play, terminate, etc.).

The following page explains how to work with CTBCMCLeg directly, for lower-level applications that don't want the convenience of the CAF Call framework

Working with CMC Call Legs

CAF API layer

A higher-level API uses the base classes CTBCMCLeg and CTBCMCMixer, but adds the following functionalities: - Simplification of call legs creations through single functions (AddIncoming, AddOutgoing, CreateMixer) - Centralizing reception of events from call legs and mixers in to a single "Call Flow" (CTBCAFCallFlow), which deals with inter-relations between legs and mixers. - Auto-destruction of call legs (CTBCMCLeg) and mixers (CTBCMCMixer) through usage of "smart" pointers. - Auto-destruction of the call flow (CTBCAFCallFlow) upon destruction of last leg/mixer.

The following page explains how to work with CAF Call leg framework (CTBCAFCallLeg, CTBCAFCallFlow, CTBCAFCallBehavior, etc...)

Working with CAF Call Legs and behaviors

The following page provides more details on call legs re-synchronization between toolpack_engine application and user "CAF" application:

Re-synchronizing CAF call legs

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