Speech to Text Transcription with the Cloud Speech API

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Speech to Text Transcription with the Cloud Speech API

Lab 30 minutes universal_currency_alt 1 Credit show_chart Introductory
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The Speech-to-Text API lets you transcribe audio speech files to text files in over 80 languages.

In this lab you send an audio file to the Speech API for transcription.

What you'll learn

In this lab, you explore the following:

  • Creating a Speech-to-Text API request and calling the API with curl
  • Calling the Speech-to-Text API with audio files in a different language

Setup and requirements

Before you click the Start Lab button

Read these instructions. Labs are timed and you cannot pause them. The timer, which starts when you click Start Lab, shows how long Google Cloud resources will be made available to you.

This hands-on lab lets you do the lab activities yourself in a real cloud environment, not in a simulation or demo environment. It does so by giving you new, temporary credentials that you use to sign in and access Google Cloud for the duration of the lab.

To complete this lab, you need:

  • Access to a standard internet browser (Chrome browser recommended).
Note: Use an Incognito or private browser window to run this lab. This prevents any conflicts between your personal account and the Student account, which may cause extra charges incurred to your personal account.
  • Time to complete the lab---remember, once you start, you cannot pause a lab.
Note: If you already have your own personal Google Cloud account or project, do not use it for this lab to avoid extra charges to your account.

How to start your lab and sign in to the Google Cloud console

  1. Click the Start Lab button. If you need to pay for the lab, a pop-up opens for you to select your payment method. On the left is the Lab Details panel with the following:

    • The Open Google Cloud console button
    • Time remaining
    • The temporary credentials that you must use for this lab
    • Other information, if needed, to step through this lab
  2. Click Open Google Cloud console (or right-click and select Open Link in Incognito Window if you are running the Chrome browser).

    The lab spins up resources, and then opens another tab that shows the Sign in page.

    Tip: Arrange the tabs in separate windows, side-by-side.

    Note: If you see the Choose an account dialog, click Use Another Account.
  3. If necessary, copy the Username below and paste it into the Sign in dialog.

    {{{user_0.username | "Username"}}}

    You can also find the Username in the Lab Details panel.

  4. Click Next.

  5. Copy the Password below and paste it into the Welcome dialog.

    {{{user_0.password | "Password"}}}

    You can also find the Password in the Lab Details panel.

  6. Click Next.

    Important: You must use the credentials the lab provides you. Do not use your Google Cloud account credentials. Note: Using your own Google Cloud account for this lab may incur extra charges.
  7. Click through the subsequent pages:

    • Accept the terms and conditions.
    • Do not add recovery options or two-factor authentication (because this is a temporary account).
    • Do not sign up for free trials.

After a few moments, the Google Cloud console opens in this tab.

Note: To view a menu with a list of Google Cloud products and services, click the Navigation menu at the top-left. Navigation menu icon

Task 1. Create an API key

Since you use curl to send a request to the Speech-to-Text API, you need to generate an API key to pass in your request URL.

  1. To create an API key, on the Navigation menu (Navigation menu icon) click APIs & services > Credentials.

  2. Click Create credentials and select API key.

  3. Copy and record the key you just generated to use later in this lab.

  4. Click Close.

Click Check my progress to verify the objective.

Create an API Key

Now save your key to an environment variable to avoid having to insert the value of your API key in each request.

  1. To perform the next steps, connect to the linux-instance provisioned for you via SSH:

On the Navigation menu (Navigation menu icon) click Compute Engine > VM Instances.

Notice the linux-instance VM in the VM instances list. VM details are to the right of the VM name.

  1. Click SSH to the right of the linux-instance VM name.

An interactive shell opens. Use this to perform the next operations.

  1. In the shell (SSH) run the following, replacing <your_api_key> with the key you just copied:

Task 2. Create your API request

Note: This lab uses a pre-recorded file that's available on Cloud Storage: gs://cloud-samples-data/speech/brooklyn_bridge.flac. Before sending it to the Speech-to-Text API, you can listen to this file.
  1. Build your request to the API in a request.json file. Create the request.json file:
touch request.json
  1. Open the file using your preferred command line editor (nano, vim, emacs) or gcloud and then add the following to your request.json file, using the uri value of the sample raw audio file:
{ "config": { "encoding":"FLAC", "languageCode": "en-US" }, "audio": { "uri":"gs://cloud-samples-data/speech/brooklyn_bridge.flac" } }
  1. Save the file as needed.

The request body has a config and audio object.

In config, you tell the Speech-to-Text API how to process the request:

  • The encoding parameter tells the API which type of audio encoding you're using while the file is being sent to the API. FLAC is the encoding type for .raw files (Learn more about encoding types from the RecognitionConfig reference).
  • languageCode defaults to English if left out of the request.

There are other parameters you can add to your config object, but encoding is the only required one.

In the audio object, you pass the API the uri of the audio file, which is stored in Cloud Storage for this lab.

Click Check my progress to verify the objective.

Create your Speech API request

Now you're ready to call the Speech-to-Text API!

Task 3. Call the Speech-to-Text API

  1. Pass your request body, along with the API key environment variable, to the API with the following curl command (all in one single command line):
curl -s -X POST -H "Content-Type: application/json" --data-binary @request.json \ "${API_KEY}" > result.json

Your response is stored in a file named as result.json.

  1. To see the contents of file you can use:
cat result.json

The response returned by the curl command look something like this:

{ "results": [ { "alternatives": [ { "transcript": "how old is the Brooklyn Bridge", "confidence": 0.98216057 } ], "resultEndTime": "1.770s", "languageCode": "en-us" } ], "totalBilledTime": "15s" }

The transcript value returns the Speech API's text transcription of your audio file, and the confidence value indicates how sure the API is that it has accurately transcribed your audio.

Notice that you called the syncrecognize method in our request above. The Speech-to-Text API supports both synchronous and asynchronous speech to text transcription.

In this example a complete audio file was used, but you can also use the syncrecognize method to perform streaming speech to text transcription while the user is still speaking.

Click Check my progress to verify the objective.

Call the Speech API for English language

Task 4. Speech-to-Text transcription in different languages

Are you multilingual? The Speech-to-Text API supports speech to text transcription in over 100 languages!

You can change the language_code parameter in request.json. You can find a list of supported languages in the Language support guide.

Try a French audio file - (for a preview, listen here).

  1. Edit your request.json and change the content to the following:
{ "config": { "encoding":"FLAC", "languageCode": "fr" }, "audio": { "uri":"gs://cloud-samples-data/speech/corbeau_renard.flac" } }
  1. Call the Speech-to-Text by running the curl command again.

  2. See the results:

cat result.json

You should see the following response:

{ "results": [ { "alternatives": [ { "transcript": "maître corbeau sur un arbre perché Tenait dans son bec un fromage maître Renard par l'odeur alléché lui tint à peu près ce langage et bonjour monsieur du corbeau", "confidence": 0.93855613 } ], "resultEndTime": "12.630s", "languageCode": "fr-fr" } ], "totalBilledTime": "15s" }

This is a sentence from a popular French children’s tale by Jean de la Fontaine. If you’ve got audio files in another language, you can try adding them to Cloud Storage and changing the languageCode parameter in your request.

Note: API restrictions and usage limits on Cloud Speech-to-Text are documented in the Quotas and limits resource. Call the Speech API for French language


You've performed speech to text transcription with the Speech API. You passed the API the Cloud Storage URI of your audio file and reviewed the alternative of passing a base64 encoded string of your audio content.

Finish your quest

This self-paced lab is part of the Intro to ML: Language Processing and Language, Speech, Text & Translation with Google CLoud APIs quests. A quest is a series of related labs that form a learning path. Completing a quest earns you a badge to recognize your achievement. You can make your badge or badges public and link to them in your online resume or social media account. Enroll in any quest that contains this lab and get immediate completion credit. Refer to the Google Cloud Skills Boost catalog for all available quests.

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Manual Last Updated September 20, 2023

Lab Last Tested September 20, 2023

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