The configuration for the Google DFE speech module is in the res_speech_gdfe.conf file in the Asterisk configuration directory. It is a standard format Asterisk configuration file.

• service_key - (required) the path to a JSON-format Google service key or the actual key itself.
• endpoint - (optional) the URL for the DialogFlow API endpoint. Leave blank to use the default dialogflow.googleapis.com.
• vad_voice_threshold - (optional) the average absolute amplitude of a packet to consider that packet to be 'voice'. The default is 512. Valid range 0-32767.
• vad_voice_minimum_duration - (optional, milliseconds) the cumulative duration of consecutive 'voice' packets to consider the caller to be speaking. The default is 40 (milliseconds). Valid range 0-2147483647.
• vad_silence_minimum_duration - (optional, milliseconds, not implemented) the cumulative duration of consecutive non-'voice' packets to consider the caller to be not speaking. The default is 500 (milliseconds). Valid range 0-2147483647. This setting currently has no effect as the end of speech is determined by DialogFlow.

To access the DialogFlow endpoint via a proxy you must set the environment variable http_proxy to the URL of your proxy. This must be done for the Asterisk process as a whole.

Speech module behavior may be modified by using the SPEECH_ENGINE dialplan function. Available settings are:

• session_id - set a session identifier to use when making DialogFlow API calls. This will be reflected in the history of the agent on the DialogFlow console. A default random value will be used if not provided.
• project_id - set the project identifier to use when making DialogFlow API calls. This setting is required in order to determine which agent to use.
• language - set the language for the recognition engine for when doing intent detection and prompt generation. The default is en. The engine has no visibility into the channel language -- if it has changed it is still necessary to set the engine language.
• voice_threshold - set the average absolute amplitude of a packet to consider that packet to be 'voice' (see vad_voice_threshold, above).
• voice_duration - set the cumulative duration of consecutive 'voice' packets to consider the caller to be speaking (see vad_voice_minimum_duration, above).
• silence_duration - the cumulative duration of consecutive non-'voice' packets to consider the caller to be not speaking (see vad_silence_minimum_duration, above).

Before detecting intent for your calls, you must first:

1. create the speech resource (only do this once),
2. set the project_id, and

same =>   n,SpeechCreate()
same =>   n,Set(SPEECH_ENGINE(project_id)=my-project-12345)

To detect intent from voice, you should call SpeechBackground to send audio to the module. You may specify a prompt to play while performing the detection.

same =>   n,SpeechBackground(hello-world)

To detect intent by event, you should activate a grammar with the name event:{your event name} prior to calling SpeechBackground. The SpeechBackground application will return immediately -- you should not include a prompt.

same =>   n,SpeechActivateGrammar(event:welcome)
same =>   n,SpeechBackground(hello-world)

The DialogFlow module returns the following results (when available):

• response_id - the unique identifier for this response
• query_text - the text of the speech recognized by DialogFlow
• language_code - the detected language of the recognized speech
• action - the action for the detected intent
• fulfillment_text - the text of the next prompt for the caller
• intent_name - the API name of the intent detected
• intent_display_name - the displayed name of the intent detected
• raw_score - the raw recognition score
• fulfillment_message_N_text_M - the fulfillment text messages from the response
• fulfillment_message_N_simple_response_M - the simple response fulfillment messages from the response
• fulfillment_message_N_telephony_play_audio - a URI from the telephony audio response fulfillment message
• fulfillment_message_N_telephony_synthesize_speech - text or SSML from the telephony synthesized speech fulfillment message
• fulfillment_message_N_telephony_transfer_call - a phone number for transferring from the telephony transfer call fulfillment message
• fulfillment_message_N_telephony_terminate_call - a flag indicating that the fulfillment message requested call termination
• fulfillment_audio - a path to audio corresponding to the fulfillment text

(those with N or M in the name may occur multiple times with different indexes in those positions)