Speech-to-Text with IBM Watson and PHP

I needed a speech to text engine for a project that I'm working on at Nexmo, and we settled on the IBM Watson speech-to-text engine.

Unfortunately, IBM don't have an official PHP client library and the ones that I could find on GitHub didn't support speech-to-text. Here's how I took an mp3 and retrieved the text within it

First, sign up for IBM Bluemix. It may have already created you a speech-to-text project. If so, click on show at next to credentials at the bottom and make a note of the username and password - we'll need them later.

If it didn't, you'll need to do the following

• Click on Create project in the top right

• Click Get Watson Services

• Select Speech to Text

• Click Add Services on the right

• Give your project a name

• Click Create a project

Once you have a your credentials, it's time to make the request. We're going to use Guzzle, so let's install it first:

bash
composer require guzzlehttp/guzzle

Once it's installed, we can send the file off to IBM by creating a client and making a POST request to https://stream.watsonplatform.net/spech-to-text/api/v1/recognize using the credentials that we make a note of earlier.

php
<?php
require_once 'vendor/autoload.php';
$client = new GuzzleHttp\Client([
   'base_uri' => 'https://stream.watsonplatform.net/'
]);
$audio = fopen('/path/to/audio.mp3', 'r');
$resp = $client->request('POST', 'speech-to-text/api/v1/recognize', [
   'auth' => ['username', 'password'],
   'headers' => [
      'Content-Type' => 'audio/mpeg',
   ],
   'body' => $audio
]);
echo $resp->getBody();

The IBM API will respond with a JSON document containing the transcribed text. Here's the response from my test call where I said "Hello Watson, this is a test, will you transcribe this correctly for me please"

json
{
  "results": [
    {
      "alternatives": [
        {
          "confidence": 0.55,
          "transcript": "hello Watson "
        }
      ],
      "final": true
    },
    {
      "alternatives": [
        {
          "confidence": 0.998,
          "transcript": "this is a test "
        }
      ],
      "final": true
    },
    {
      "alternatives": [
        {
          "confidence": 0.735,
          "transcript": "were you transcribe this correctly for me please "
        }
      ],
      "final": true
    }
  ],
  "result_index": 0
}

Overall I think it did pretty well, considering that I was speaking fairly quickly in to the default laptop microphone.