Voicemail Transcription Using Ruby

Overview

This guide shows how to transcribe voicemail and send the transcription via SMS.

Prerequisites

To get started, you need a Plivo account — sign up with your work email address if you don’t have one already. You must have a voice- and SMS-enabled Plivo phone number to receive calls and send SMS messages; you can rent numbers from the Numbers page of the Plivo console, or by using the Numbers API. If this is your first time using Plivo APIs, follow our instructions to set up a Ruby development environment and a web server and safely expose that server to the internet.

Create a Rails controller to implement voicemail transcription

Change to the project directory and run this command to create a Rails controller for inbound calls.

$ rails generate controller Plivo voice

This command generates a controller named plivo_controller in the app/controllers/ directory and a respective view in app/views/plivo. We can delete the view as we do not need it.

$ rm app/views/plivo/voice.html.erb

Edit app/controllers/plivo_controller.rb and paste this code into the PlivoController class.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
include Plivo
include Plivo::XML
include Plivo::Exceptions

class PlivoController < ApplicationController
  skip_before_action :verify_authenticity_token
	def voicemail
		response = Response.new
		response.addSpeak('Please leave a message after the beep. Press the star key when you\'re done.')
		params = {
      		transcriptionType: 'auto',
      		transcriptionUrl: url_for(action: 'transcriptionUrl', controller: 'plivo', only_path: false, protocol: 'https'),
			action: url_for(action: 'actionUrl', controller: 'plivo', only_path: false, protocol: 'https'),
			maxLength: '30',
			finishOnKey: '*'
		}
		response.addRecord(params)

		second_speak_body = 'Recording not received.'
		response.addSpeak(second_speak_body)
				xml = PlivoXML.new(response)
		render xml: xml.to_xml
	end

  def transcriptionUrl
    response = params
		api = RestClient.new("<auth_id>","<auth_token>")
		message_response = api.messages.create(
			src: "<sender_id>",
			dst: "<destination_number>",
			text: "You have a new transcription: "+params[:transcription]
		)
		puts message_response
		puts response
    render status: :ok, json: @controller.to_json
  end

  def actionUrl
    response = params
    puts response
    render status: :ok , json: @controller.to_json
  end
end

Replace the auth placeholders with your authentication credentials from the Plivo console. Replace the phone number placeholders with actual phone numbers in E.164 format (for example, +12025551234).

Add a route

To add a route for the inbound function in the PlivoController class, edit config/routes.rb and add this line after the inbound route.

  post 'plivo/voicemail'
  post 'plivo/transcriptionUrl'
  post 'plivo/actionUrl'

Start the Rails server

$ rails server

You should see your basic server application in action at http://localhost:3000/plivo/voicemail/.

Set up ngrok to expose your local server to the internet.

Create a Plivo application for voicemail transcription

Associate the Rails controller you created with Plivo by creating a Plivo application. Visit Voice > Applications in the Plivo console and click on Add New Application, or use Plivo’s Application API.

Give your application a name — we called ours Voicemail-Transcription. Enter the server URL you want to use (for example https://<yourdomain>.com/voicemail/) in the Answer URL field and set the method to POST. Click Create Application to save your application.

Assign a Plivo number to your application

Navigate to the Numbers page and select the phone number you want to use for this application.

From the Application Type drop-down, select XML Application.

From the Plivo Application drop-down, select Voicemail-Transcription (the name we gave the application).

Click Update Number to save.

Test

Make a call to your Plivo number and leave yourself a voicemail message. You should receive a text message with the transcription.