Send a recognition request with speech adaptation

You can improve the accuracy of the transcription results you get from Speech-to-Text by using speech adaptation. The speech adaptation feature allows you to specify words and/or phrases that STT should recognize more frequently in your audio data than other alternatives that might otherwise be suggested. Speech adaptation is particularly useful for improving transcription accuracy in the following cases:

1. Your audio contains words/phrases that are likely to occur very frequently.
2. Your audio is likely to contain words that are rare (such as proper names) or words that do not exist in general use.
3. Your audio contains noise or is otherwise not very clear.

See the speech adaptation concepts page for speech adaptation and speech adaptation boost best practices information.

The following code sample demonstrates how to improve transcription accuracy by setting speech contexts in a request sent to Speech-to-Text API. See the class tokens page for a list of the classes available for your language.

REST & CMD LINE

Refer to the speech:recognize API endpoint for complete details.

Before using any of the request data below, make the following replacements:

• language-code: the BCP-47 code of the language spoken in your audio clip.
• phrases-to-boost: phrase or phrases that you want Speech-to-Text to boost, as an array of strings.
• storage-bucket: a Cloud Storage bucket.
• input-audio: the audio data that you want to transcribe.

HTTP method and URL:

POST https://speech.googleapis.com/v1p1beta1/speech:recognize

Request JSON body:

{
  "config":{
      "languageCode":"language-code",
      "speechContexts":[{
          "phrases":[phrases-to-boost],
          "boost": 2
      }]
  },
  "audio":{
    "uri":"gs:storage-bucket/input-file"
  }
}

To send your request, expand one of these options:

curl (Linux, macOS, or Cloud Shell)

Note: Ensure you have set the GOOGLE_APPLICATION_CREDENTIALS environment variable to your service account private key file path.

Save the request body in a file called request.json, and execute the following command:

curl -X POST \
-H "Authorization: Bearer "$(gcloud auth application-default print-access-token) \
-H "Content-Type: application/json; charset=utf-8" \
-d @request.json \
https://speech.googleapis.com/v1p1beta1/speech:recognize

PowerShell (Windows)

Note: Ensure you have set the GOOGLE_APPLICATION_CREDENTIALS environment variable to your service account private key file path.

Save the request body in a file called request.json, and execute the following command:

$cred = gcloud auth application-default print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }

Invoke-WebRequest `
  -Method POST `
  -Headers $headers `
  -ContentType: "application/json; charset=utf-8" `
  -InFile request.json `
  -Uri "https://speech.googleapis.com/v1p1beta1/speech:recognize" | Select-Object -Expand Content

You should receive a JSON response similar to the following:

{
  "results": [
    {
      "alternatives": [
        {
          "transcript": "When deciding whether to bring an umbrella, I consider the weather",
          "confidence": 0.9463943
        }
      ],
      "languageCode": "en-us"
    }
  ]
}

Java

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import com.google.cloud.speech.v1.RecognitionAudio;
import com.google.cloud.speech.v1.RecognitionConfig;
import com.google.cloud.speech.v1.RecognizeRequest;
import com.google.cloud.speech.v1.RecognizeResponse;
import com.google.cloud.speech.v1.SpeechClient;
import com.google.cloud.speech.v1.SpeechContext;
import com.google.cloud.speech.v1.SpeechRecognitionAlternative;
import com.google.cloud.speech.v1.SpeechRecognitionResult;
import java.io.IOException;

class TranscribeContextClasses {

  void transcribeContextClasses() throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String storageUri = "gs://YOUR_BUCKET_ID/path/to/your/file.wav";
    transcribeContextClasses(storageUri);
  }

  // Provides "hints" to the speech recognizer to favor specific classes of words in the results.
  static void transcribeContextClasses(String storageUri) throws IOException {
    // Initialize client that will be used to send requests. This client only needs to be created
    // once, and can be reused for multiple requests. After completing all of your requests, call
    // the "close" method on the client to safely clean up any remaining background resources.
    try (SpeechClient speechClient = SpeechClient.create()) {
      // SpeechContext: to configure your speech_context see:
      // https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#speechcontext
      // Full list of supported phrases (class tokens) here:
      // https://cloud.google.com/speech-to-text/docs/class-tokens
      SpeechContext speechContext = SpeechContext.newBuilder().addPhrases("$TIME").build();

      // RecognitionConfig: to configure your encoding and sample_rate_hertz, see:
      // https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#recognitionconfig
      RecognitionConfig config =
          RecognitionConfig.newBuilder()
              .setEncoding(RecognitionConfig.AudioEncoding.LINEAR16)
              .setSampleRateHertz(8000)
              .setLanguageCode("en-US")
              .addSpeechContexts(speechContext)
              .build();

      // Set the path to your audio file
      RecognitionAudio audio = RecognitionAudio.newBuilder().setUri(storageUri).build();

      // Build the request
      RecognizeRequest request =
          RecognizeRequest.newBuilder().setConfig(config).setAudio(audio).build();

      // Perform the request
      RecognizeResponse response = speechClient.recognize(request);

      for (SpeechRecognitionResult result : response.getResultsList()) {
        // First alternative is the most probable result
        SpeechRecognitionAlternative alternative = result.getAlternativesList().get(0);
        System.out.printf("Transcript: %s\n", alternative.getTranscript());
      }
    }
  }
}

Node.js

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// Provides "hints" to the speech recognizer to favor
// specific classes of words in the results.

// Imports the Google Cloud client library
const speech = require('@google-cloud/speech');

// Creates a client
const client = new speech.SpeechClient();

async function transcribeContextClasses() {
  // storageUri = 'gs://YOUR_BUCKET_ID/path/to/your/file.wav'
  const audio = {
    uri: storageUri,
  };

  // SpeechContext: to configure your speech_context see:
  // https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#speechcontext
  // Full list of supported phrases(class tokens) here:
  // https://cloud.google.com/speech-to-text/docs/class-tokens
  const speechContext = {
    phrases: ['$TIME'],
  };

  // RecognitionConfig: to configure your encoding and sample_rate_hertz, see:
  // https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#recognitionconfig
  const config = {
    encoding: 'LINEAR16',
    sampleRateHertz: 8000,
    languageCode: 'en-US',
    speechContexts: [speechContext],
  };

  const request = {
    config: config,
    audio: audio,
  };

  // Detects speech in the audio file.
  const [response] = await client.recognize(request);
  response.results.forEach((result, index) => {
    const transcript = result.alternatives[0].transcript;
    console.log('-'.repeat(20));
    console.log(`First alternative of result ${index}`);
    console.log(`Transcript: ${transcript}`);
  });
}

transcribeContextClasses();

Python

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from google.cloud import speech

client = speech.SpeechClient()

# storage_uri = 'gs://YOUR_BUCKET_ID/path/to/your/file.wav'
audio = speech.RecognitionAudio(uri=storage_uri)

# SpeechContext: to configure your speech_context see:
# https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#speechcontext
# Full list of supported phrases (class tokens) here:
# https://cloud.google.com/speech-to-text/docs/class-tokens
speech_context = speech.SpeechContext(phrases=["$TIME"])

# RecognitionConfig: to configure your encoding and sample_rate_hertz, see:
# https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#recognitionconfig
config = speech.RecognitionConfig(
    encoding=speech.RecognitionConfig.AudioEncoding.LINEAR16,
    sample_rate_hertz=8000,
    language_code="en-US",
    speech_contexts=[speech_context],
)

response = client.recognize(config=config, audio=audio)

for i, result in enumerate(response.results):
    alternative = result.alternatives[0]
    print("-" * 20)
    print("First alternative of result {}".format(i))
    print("Transcript: {}".format(alternative.transcript))

Go

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import (
	"context"
	"fmt"
	"io"
	"strings"

	speech "cloud.google.com/go/speech/apiv1"
	speechpb "google.golang.org/genproto/googleapis/cloud/speech/v1"
)

// contextClasses provides "hints" to the speech recognizer
// to favour specific classes of words in the results.
func contextClasses(w io.Writer, gcsURI string) error {
	ctx := context.Background()

	client, err := speech.NewClient(ctx)
	if err != nil {
		return fmt.Errorf("NewClient: %v", err)
	}
	defer client.Close()

	// SpeechContext: to configure your speech_context see:
	// https://cloud.google.com/speech-to-text/docs/reference/rpc/google.cloud.speech.v1#speechcontext
	// Full list of supported phrases (class tokens) here:
	// https://cloud.google.com/speech-to-text/docs/class-tokens
	// In this instance, the use of "$TIME" favours time of day detections.
	speechContext := &speechpb.SpeechContext{Phrases: []string{"$TIME"}}

	resp, err := client.Recognize(ctx, &speechpb.RecognizeRequest{
		Config: &speechpb.RecognitionConfig{
			Encoding:        speechpb.RecognitionConfig_LINEAR16,
			SampleRateHertz: 8000,
			LanguageCode:    "en-US",
			SpeechContexts:  []*speechpb.SpeechContext{speechContext},
		},
		Audio: &speechpb.RecognitionAudio{
			AudioSource: &speechpb.RecognitionAudio_Uri{Uri: gcsURI},
		},
	})
	if err != nil {
		return fmt.Errorf("Recognize: %v", err)
	}

	// Print the results.
	for i, result := range resp.Results {
		fmt.Fprintf(w, "%s\n", strings.Repeat("-", 20))
		fmt.Fprintf(w, "Result %d\n", i+1)
		for j, alternative := range result.Alternatives {
			fmt.Fprintf(w, "Alternative %d: %s\n", j+1, alternative.Transcript)
		}
	}
	return nil
}