Rayo allows for the third-party control of media sessions such as telephone calls. A common requirement in telephony applications is to establish the progress characteristics of the session, such as dtmf, fax or modem tones, or to differentiate between a human and an answering machine. This specification extends the core Rayo specification, and specifically its Input component to describe a protocol for establishing such progress analysis and gathering its results.
This section describes the form, function and order of Rayo stanzas sent across the wire, and the circumstances in which they apply and/or may arise.
CPA is achieved as a special case of the core input component. All rules regarding component execution and the input component in particular apply from the core specification. When a call's controlling party wishes to begin detection of signals from the suported set, it SHOULD begin an input component with the mode attribute set as 'cpa'.
The grammars supplied determine the types of signal detected and parameters applied to their detection. The grammars MUST be referenced by URI in the format described below. If a Rayo server supports this specification, it MUST invoke its supported CPA function using the parameters provided from the grammars; if it does not support this specification or any of the supplied parameters within the grammar, it MUST raise an error according to the rules in the core specification.
The server MUST validate that it has appropriate resources/mechanisms to collect the requested signals before acknowledging the component creation.
If the meta-attribute named 'terminate' is set to true in the grammar, the component MUST terminate on the first signal match it detects. If it is set to false, signals MUST be reported as events until the component is instructed to stop.
The input completion reason MUST be one of the supported reasons from the core specification or a signal, indicating that the CPA engine detected one of the requested signals. Any signals other than those requested by the input grammar should be ignored.
The grammar URI declares the signal type of interest and the parameters which apply to their detection. The URI should be composed of a URN from the following list of allowed signal types, and parameters to modify their detection as a query string. The names and allowed values of these parameters are implementation specific. Servers MUST support one reserved parameter named 'terminate', whose value indicates the termination behaviour of the component on signal detection as described above.
Describes a detected signal.
The attributes of the <grammar/> element are as follows.
|type||Indicates the type of signal detected.||Any URI value from the listed signal types||none||REQUIRED|
|duration||Indicates the duration of the received signal in milliseconds||An integer value in milliseconds.||none||OPTIONAL|
|value||Indicates the value of the signal received if applicable.||For dtmf tones it is the digit detected, for speech may be human|machine|notsure and for beeps may be a frequency in Hz.||none||OPTIONAL|
Signal types may be one of the following:
|urn:xmpp:rayo:cpa:beep:1||Detect a beep.|
|urn:xmpp:rayo:cpa:dtmf:1||Detect DTMF tones.|
|urn:xmpp:rayo:cpa:vad:1||Detect voice activity.|
|urn:xmpp:rayo:cpa:speech:1||Detect speech and decide human or machine.|
|urn:xmpp:rayo:cpa:fax-ced:1||Detect a fax CED tone.|
|urn:xmpp:rayo:cpa:fax-cng:1||Detect a fax CNG tone.|
|urn:xmpp:rayo:cpa:ring:1||Detect a ringing tone.|
|urn:xmpp:rayo:cpa:busy:1||Detect a busy tone.|
|urn:xmpp:rayo:cpa:congestion:1||Detect a congestion tone.|
|urn:xmpp:rayo:cpa:sit:1||Detect a Special Information Tone.|
|urn:xmpp:rayo:cpa:modem:1||Detect a modem tone.|
|urn:xmpp:rayo:cpa:offhook:1||Detect an off-hook tone.|
If a Rayo server supports Rayo CPA, it MUST advertise that fact by returning a feature of "urn:xmpp:rayo|cpa:0" (see Namespace Versioning regarding the possibility of incrementing the version number) in response to a Service Discovery (XEP-0030)  information request.
In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in Entity Capabilities (XEP-0115) . However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
A server MUST document any cases where its behaviour differs from that in this specification (such as lack of support for particular options/components/etc) and return an error whenever a command is not understood. A server MUST NOT silently ignore any instructions.
This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) .
This specification defines the following XML namespaces:
If the protocol defined in this specification undergoes a major revision that is not fully backward-compatible with an older version, or that contains significant new features, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.
The authors would like to acknowledge the input of teams at Tropo Inc, Mojo Lingo and Grasshopper in the development of this specification.
Specific individuals who have contributed to the specification or to software significant to its completion include:
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