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Adding Asterisk external speech to text application

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This patch adds basic functionality for translating speech to text, using
the Google speech API, from audio received over a websocket after a successful
negotiation with Asterisk using the Asterisk External Application Protocol.
This commit is contained in:
Kevin Harwell 2022-02-15 13:05:43 -06:00
commit 1f701bd265
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# Asterisk External Speech to Text application
This package contains an example Node.js program that uses the [Asterisk External Application Protocol](https://wiki.asterisk.org/wiki/display/AST/Asterisk+External+Application+Protocol) (AEAP) to facilitate external speech to text translation in Asterisk.
## Description
#### Background
For a while now Asterisk has had to ability to translate speech to text via its [Speech Recognition API](https://wiki.asterisk.org/wiki/display/AST/Speech+Recognition+API). Historically though, creating a new speech recognition engine required writing a new Asterisk module, typically written in "C", that implemented the backend API. Now, with the advent of AEAP, the backend speech API is abstracted away and translation can be done externally in the programming language of one's choice.
#### Example Program
This program acts as a mediator between Asterisk and the Google speech provider. Creating a websocket server it listens for incoming client connections from Asterisk. Once a connection is established, and a successful negotiation takes place using AEAP for speech audio can then be sent from Asterisk to the application, which then forwards it to the Google speech provider. Upon a confidence speech to text result received from Google, the application sends the result to Asterisk via an AEAP message.
Speech recognition will continue until the client closes, or an error occurs.
## Dependencies
* Node.js
* [Google Speech API](https://cloud.google.com/speech-to-text/docs/) credentials set in environment variable [GOOGLE_APPLICATION_CREDENTIALS](https://cloud.google.com/docs/authentication/getting-started).
## Installation
Run `npm install` from the top of the source tree. This will install the required npm packages.
## Usage
To start the websocket server on the default port (9099):
```
$ index.js
```
Or to have it listen on a different port:
```
$ index.js --port=<port number>
```
To stop the server press `Ctrl-C`
## Example Asterisk Configuration:
Configure an AEAP client in [*aeap.conf*](https://github.com/asterisk/asterisk/blob/master/configs/samples/aeap.conf.sample):
```
[my-speech-to-text]
type=client
codecs=!all,ulaw
url=ws://127.0.0.1:9099
protocol=speech_to_text
```
This will configure a "speech engine" in Asterisk that connects to the external application. When the [Asterisk Speech Recognition API](https://wiki.asterisk.org/wiki/display/AST/Speech+Recognition+API) is employed in dialplan using the above "engine", this configuration is activated and a websocket client attempts to connect to the given URL. Next, create an extension that utilizes the speech API dialplan functions, and on *SpeechCreate* give the client id specified in *aeap.conf* as the "engine" name. Example *extensions.conf*:
```
exten => 550,1,NoOp()
same => n,Answer()
same => n,SpeechCreate(my-speech-to-text)
same => n,SpeechStart()
same => n,SpeechBackground(hello-world)
same => n,Verbose(0,${SPEECH_TEXT(0)})
same => n,SpeechDestroy()
same => n,Hangup()
```
If things are configured correctly, and the sample program found here is listening at the configured address/port then when a caller dials extension `550` the following should occur:
1. Asterisk connects via websocket to the remote application.
2. The caller hears "Hello World" played back.
3. After hearing "Hello World" any spoken audio from the caller is forwarded to the remote application.
4. Once the caller is done speaking their spoken text is printed on the Asterisk CLI.
5. The Client disconnects from remote application
6. The call is hung up.

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#!/usr/bin/env node
/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const { Codecs } = require("./lib/codecs");
const { Languages } = require("./lib/languages");
const { getProvider } = require("./lib/provider");
const { getServer } = require("./lib/server");
const { dispatch } = require("./lib/dispatcher");
const argv = require("yargs/yargs")(process.argv.slice(2))
.command("$0 [options]", "Start a speech to text server", {
port: {
alias: "p",
desc: "Port to listen on",
default: 9099,
type: "number",
group: "Server",
},
})
.strict()
.argv;
const codecs = new Codecs(argv);
const languages = new Languages(argv);
const server = getServer("ws", argv);
server.on("connection", (client) => {
dispatch({
codecs: codecs,
languages: languages,
transport: client,
provider: getProvider("google", argv),
});
});
process.on("SIGINT", () => {
server.close();
process.exit(0);
});
process.on("SIGTERM", () => {
server.close();
process.exit(0);
});

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/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const utils = require("./utils");
/**
* Supported codecs
*/
const supported = [
{
"name": "ulaw",
"sampleRate": 8000,
"attributes" : [],
},
{
"name": "slin16",
"sampleRate": 16000,
"attributes" : [],
},
{
"name": "opus",
"sampleRate": 48000,
"attributes" : [],
},
];
/**
* Checks if given codecs match.
*
* @param {Object} obj1 - A codec object
* @param {Object} obj2 - A codec object
* @return {boolean} true if codecs match otherwise false.
*/
function equal(obj1, obj2) {
return obj1.name === obj2.name;
}
/**
* Converts codecs to a comma separated string of codec names.
*
* @param {Object|Object[]} objs - Codecs to convert
* @return {string} A comma separated string of codec names.
*/
function toString(objs) {
if (!Array.isArray(objs)) {
objs = [objs];
}
return objs.map(o => o.name).join(", ");
}
/** @class Codecs. */
class Codecs {
/**
* Creates an instance of Codecs.
*
* @param {Object} options - Codec options
*/
constructor(options) {
this.codecs = options.codecs ?
utils.intersect(supported, options.codecs, equal) : supported;
this.selected = this.codecs[0]; // Default to first in list
}
/**
* Selects the first matching codec between supported and given codecs
*
* @param {Object|Object[]} codecs - Codecs to intersect with supported
* @return The first selected codec
*/
first(codecs) {
try {
let res = utils.first(this.codecs, codecs, equal);
if (res) {
return res;
}
} catch (e) {
}
throw new Error("Codec " + toString(codecs) + " not supported");
}
};
module.exports = {
Codecs,
}

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/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const { randomUUID } = require('crypto');
function handleError(e, msg) {
msg.error_msg = e.message;
}
function sendMessage(speech, msg) {
speech.transport.send(JSON.stringify(msg), { binary: false });
}
function sendSetRequest(speech, params) {
request = {
request: "set",
id: randomUUID(),
params,
};
sendMessage(speech, request);
}
function handleGetRequest(speech, request, response) {
if (!request.params) {
throw new Error("Missing request parameters");
}
let params = {};
for (let p of request.params) {
if (p === "codec") {
params.codecs = speech.codecs.selected;
} else if (p === "language") {
params.language = speech.languages.selected;
} else if (p === "results") {
params.results = speech.provider.results.splice(0);
} else {
console.warn("Ignoring unsupported parameter '" + k + "' in '" +
request.request + "' request");
}
}
response.params = params;
}
function handleSetRequest(speech, request, response) {
if (!request.codecs || !request.params) {
throw new Error("Missing request parameters");
}
/*
* It's all or nothing for an incoming set request. So first validate
* all values, then set newly selected, and lastly set the response.
*/
let codec = null;
let params = {};
if (request.codecs) {
codec = speech.codecs.first(request.codecs);
}
for (let [k, v] of Object.entries(request.params)) {
if (k == "language") {
params.language = speech.languages.first(v);
} else {
console.warn("Ignoring unsupported parameter '" + k + "' in '" +
request.request + "' request");
}
}
if (codec) {
response.codecs = [speech.codecs.selected = codec];
}
if (Object.keys(params).length) {
if (params.language) {
speech.languages.selected = params.language;
}
response.params = params;
}
if (response.codecs || response.params) {
// Start/Restart provider if any parameters were changed
speech.provider.restart({
codec: speech.codecs.selected,
language: speech.languages.selected,
});
}
}
function handleRequest(speech, msg) {
const handlers = {
"get": handleGetRequest,
"set": handleSetRequest,
"setup": handleSetRequest,
};
let response = { response: msg.request, id: msg.id };
try {
handlers[msg.request](speech, msg, response);
} catch (e) {
handleError(e, response);
}
return response;
}
function handleResponse(speech, msg) {
return null; // TODO
}
/**
* Manages configuration, communication, messaging, and data between
* a connected transport and speech provider.
*
* @param {Object} speech - speech object
* @param {Object} speech.codecs - allowed codec(s)
* @param {Object} speech.languages - allowed language(s)
* @param {Object} speech.transport - remote connection
* @param {Object} speech.provider - speech provider
*/
function dispatch(speech) {
speech.transport.on("close", () => {
speech.provider.end();
});
speech.transport.on("message", (data, isBinary) => {
if (isBinary) {
speech.provider.write(data);
return;
}
console.debug("message: " + data);
let msg = JSON.parse(data);
if (msg.hasOwnProperty('request')) {
msg = handleRequest(speech, msg);
} else if (msg.hasOwnProperty('response')) {
msg = handleResponse(speech, msg);
} else {
msg = null;
}
if (msg) {
sendMessage(speech, msg);
}
});
speech.provider.on("result", (result) => {
sendSetRequest(speech, { results: [ result ] });
});
}
module.exports = {
dispatch,
}

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/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const utils = require("./utils");
/**
* Supported languages
*/
const supported = [
"en-US",
];
/**
* Converts languages to a comma separated string of language names.
*
* @param {Object|Object[]} objs - Languages to convert
* @return {string} A comma separated string of language names.
*/
function toString(objs) {
if (!Array.isArray(objs)) {
objs = [objs];
}
return objs.join(", ");
}
/** @class Languages. */
class Languages {
/**
* Creates an instance of Languages.
*
* @param {Object} options - Language options
*/
constructor(options) {
this.languages = options.languages ?
utils.intersect(supported, options.languages) : supported;
this.selected = this.languages[0]; // Default to first in list
}
/**
* Selects the first matching language between supported and given languages
*
* @param {Object|Object[]} languages - Languages to intersect with supported
* @return The first selected language
*/
first(languages) {
try {
let res = utils.first(this.languages, languages);
if (res) {
return res;
}
} catch (e) {
}
throw new Error("Language " + toString(languages) + " not supported");
}
};
module.exports = {
Languages,
}

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/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const { Writable } = require('stream');
const speech = require('@google-cloud/speech');
/*
* For speech provider implementer.
*
* Basic Provider public interface:
*
* function setConfig(config) - sets configuration used by recognize stream
* function start(config) - starts the recognize stream
* function restart(config) - restarts the recognize stream
* function end() - stops recognize and writable stream
* function write(data) - writes data to the writable stream
* event result(result) - triggered when a result is received from provider
* field results[] - cache of received results (oldest to newest)
*
* Basic result object public interface:
*
* result = {
* text: <the recognized string value>
* score: <percent based accuracy/confidence score>
* };
*/
/*
* Google Speech API:
* https://googleapis.dev/nodejs/speech/latest/
*
* Google infinite streaming speech example:
* https://cloud.google.com/speech-to-text/docs/samples/speech-transcribe-infinite-streaming
*
* Nodejs stream API:
* https://nodejs.org/api/stream.html
*/
// const encoding = 'Encoding of the audio file, e.g. LINEAR16';
// const sampleRateHertz = 16000;
// const languageCode = 'BCP-47 language code with regional subtags, e.g. en-US';
// const limit = 10000; // ms - set to low number for demo purposes
const DEFAULT_ENCODING = "MULAW";
const DEFAULT_SAMPLE_RATE = 8000;
const DEFAULT_LANGUAGE = "en-US";
const DEFAULT_RESTART_TIME = 10; // in seconds
const DEFAULT_MAX_RESULTS = 100;
/**
* @class GoogleProvider.
*
* Start, restart, and stop Google speech to text recognition. Results are
* emitted via a "result" event that is passed the following object:
*
* result = {
* text: <the recognized string value>
* score: <percent based accuracy/confidence score>
* };
*
* @extends Writable
*/
class GoogleProvider extends Writable {
/* Mapped encodings supported by Google */
static encodings = {
ulaw: "MULAW",
slin16: "LINEAR16",
opus: "OGG Opus",
};
/* Languages this provider supports */
static languages = [
"en-US",
];
/**
* Creates an instance of a Google provider stream.
*
* @param {Object} [options] - provider specific options
* @param {Object} [options.restartTime=10] - If specified auto-restart
* recognition stream after a given interval (in seconds)
* @param {Object} [options.maxResults=100] - The maximum number of results
* to cache before results are dropped (oldest dropped first)
*/
constructor(options) {
super();
this.config = {
encoding: DEFAULT_ENCODING,
sampleRateHertz: DEFAULT_SAMPLE_RATE,
languageCode: DEFAULT_LANGUAGE,
};
this.restartTimer = null;
this.restartTimeout = options && options.restartTime || DEFAULT_RESTART_TIME;
this.maxResults = options && options.maxResults || DEFAULT_MAX_RESULTS;
this.results = [];
this.recognizeStream = null;
}
_construct(callback) {
this.client = new speech.SpeechClient();
callback();
}
_write(chunk, encoding, callback) {
if (this.recognizeStream) {
this.recognizeStream.write(chunk);
}
callback();
}
_writev(chunks, callback) {
for (let chunk in chunks) {
this._write(chunk, null, callback);
}
callback();
}
_final(callback) {
this.stop();
this.client.close();
callback();
}
/**
* Sets the configuration to use on the recognition stream.
*
* @param {Object} [config] - configuration to set
* @param {Object} [config.codec] - the codec to map to an encoding
* @param {string} [config.language] - the language to use
*/
setConfig(config) {
if (!config) {
return;
}
let update = {};
if (config.codec) {
if (!(config.codec.name in GoogleProvider.encodings)) {
throw new Error("Codec '" + config.codec.name + " 'not supported");
}
update.encodingencoding = GoogleProvider.encodings[config.codec.name];
update.sampleRateHertz = config.codec.sampleRate;
}
if (config.language) {
if (!GoogleProvider.languages.includes(config.language)) {
throw new Error("Language '" + config.language + " 'not supported");
}
update.languageCode = config.language;
}
this.config = {...this.config, ...update};
}
/**
* Starts the recognition stream.
*
* @param {Object} [config] - configuration to use
* @param {Object} [config.codec] - the codec to map to an encoding
* @param {string} [config.language] - the language to use
*/
start(config) {
if (this.recognizeStream) {
return; // Already started
}
this.setConfig(config);
config = this.config;
const request = {
config,
interimResults: true,
};
this.recognizeStream = this.client
.streamingRecognize(request)
.on('error', (e) => {
console.error("GoogleProvider: " + e + " - ending stream");
this.end();
})
.on('data', (response) => {
if (response.results[0] && response.results[0].alternatives[0]) {
if (response.results[0].alternatives[0].confidence == 0) {
return;
}
let result = {
text: response.results[0].alternatives[0].transcript,
score: Math.round(response.results[0].alternatives[0].confidence * 100),
};
console.debug("GoogleProvider: result: " + JSON.stringify(result));
this.emit('result', result);
if (this.results.length == this.maxResults) {
this.results.shift();
}
this.results.push(result);
} else {
// stream limit reached restart?
console.debug("GoogleProvider: received response, but no result");
}
});
if (this.restartTimeout) {
/*
* Google's speech engine may stop transcribing after a while,
* so restart the recognize stream after a specified interval.
*/
this.restartTimer = setTimeout(() => this.restart(), this.restartTimeout * 1000);
}
while (this.writableCorked) {
this.uncork();
}
}
/**
* Stops the recognition stream.
*/
stop() {
if (this.restartTimer) {
clearInterval(this.restartTimer);
this.restartTimer = null;
}
if (!this.recognizeStream) {
return;
}
this.cork(); // Buffer any incoming data
this.recognizeStream.end();
this.recognizeStream = null;
}
/**
* Restarts the recognition stream.
*
* @param {Object} [config] - configuration to use
* @param {Object} [config.codec] - the codec to map to an encoding
* @param {string} [config.language] - the language to use
*/
restart(config) {
this.stop();
this.start(config);
}
}
/**
* Gets a speech provider
*
* @param {string} name - A speech provider name
* @param {Object} options - Provider specific options
* @return A speech provider.
*/
function getProvider(name, options) {
if (name == "google") {
return new GoogleProvider(options);
}
throw new Error("Unsupported speech provider '" + name + "'");
}
module.exports = {
getProvider,
}

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/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const EventEmitter = require("events");
const { WebSocketServer } = require("ws");
/*
* For server accepting clients implementer.
*
* Basic server public interface:
*
* function close() - shutdowns the server
* event connection(client) - triggered when a client connects
*
* Basic client public interface:
*
* function send(data, { binary: <boolean> }) - sends data to client
* event close() - triggered when a client closes
* event message(data, isBinary) - triggered when data is received
*/
const DEFAULT_PORT = 9099;
/**
* @class WSServer.
*
* Wrapper around a websocket server. Starts listening on a given port, and
* emits a "connection" event when a client connects.
*
* @extends EventEmitter
*/
class WSServer extends EventEmitter {
/**
* Creates an instance of a Websocket server.
*
* @param {Object} [options] - websocket server specific options
* @param {Object} [options.port=9099] - Port to listen on
*/
constructor(options) {
super();
this.port = options && options.port || DEFAULT_PORT;
this.ws = new WebSocketServer({
port: this.port,
clientTracking: true,
});
this.ws.on("listening", () => {
console.info("Server on port '" + this.port + "': started listening");
});
this.ws.on("close", () => {
console.info("Server on port '" + this.port + "': stopped listening");
});
this.ws.on("error", (error) => {
console.error(error);
});
this.ws.on("connection", (client) => {
console.info("Server on port '" + this.port + "': client connected");
/**
* Client connect event.
*
* @event WSServer#connection
* @type {object}
*/
this.emit("connection", client);
});
}
/**
* Close/Stop the server disconnecting all clients
*/
close() {
for (let client of this.ws.clients) {
console.log("WSServer: close client");
client.close();
}
this.ws.close((error) => {
console.log("error " + error);
});
}
}
/**
* Gets a server.
*
* @param {string} name - A server type name
* @param {Object} options - Server specific options
* @return A server.
*/
function getServer(name, options) {
if (name == "ws") {
return new WSServer(options);
}
throw new Error("Unsupported server type '" + name + "'");
}
module.exports = {
getServer,
}

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/*
* Copyright 2022 Sangoma Technologies Corporation
* Kevin Harwell <kharwell@sangoma.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Checks to see if given objects are equal.
*
* @param {Object} obj1
* @param {Object} obj2
* @param {requestCallback} [eq] - Object equality callback
* @return {string} A comma separated string of language names.
*/
function equals(obj1, obj2, eq) {
if (obj1 == undefined || obj1 == null ||
obj2 == undefined || obj2 == null) {
return false;
}
return obj1 == obj2 || (eq && eq(obj1, obj2));
}
/**
* Creates a list of objects that contains only those objects that are equal between
* the given lists of objects.
*
* @param {Object[]} objs1
* @param {Object[]} objs2
* @param {requestCallback} [eq] - Object equality callback
* @return {Object[]} An intersected list of objects.
*/
function intersect(objs1, objs2, eq) {
let res = [];
for (let obj1 of objs1) {
for (let obj2 of objs2) {
if (equals(obj1, obj2, eq)) {
res.push(obj1);
}
}
}
return res;
}
/**
* Finds and returns the first matching object within two given lists.
*
* @param {Object[]} objs1
* @param {Object[]} objs2
* @param {requestCallback} [eq] - Object equality callback
* @return {Object} The first matching object.
*/
function first(objs1, objs2, eq) {
if (!Array.isArray(objs1)) {
objs1 = [objs1];
}
if (!Array.isArray(objs2)) {
objs2 = [objs2];
}
return intersect(objs1, objs2, eq)[0];
}
module.exports = {
first,
intersect,
}

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{
"name": "aeap-speech-to-text",
"description": "asterisk external speech to text application",
"version": "0.1.0",
"homepage": "https://github.com/asterisk/aeap-speech-to-text#README.md",
"main": "./index.js",
"bin": "./index.js",
"license": "Apache-2.0",
"readmeFilename": "README.md",
"repository": {
"type": "git",
"url": "https://github.com/asterisk/aeap-speech-to-text.git"
},
"keywords": [
"asterisk",
"asterisk external application protocol",
"aeap",
"speech"
],
"dependencies": {
"@google-cloud/speech": "^4.9.0",
"ws": "^8.3.0",
"yargs": "^17.3.1"
}
}