How can I resolve the 'Could not deserialize speech context' error in Azure Pronunciation Assessment using JavaScript?

The error

Could not deserialize speech context. websocket error code: 1007

usually indicates that some properties in the speech context (the JSON that’s sent to the service) are malformed or not recognized. In the case of pronunciation assessment, a common pitfall is providing configuration values as plain strings rather than using the SDK’s provided enumeration values.

Below are a few adjustments you should make:

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1. Use Enumerations for Configuration

Instead of passing string values like "HundredMark" and "Phoneme", use the SDK-provided enums. For example:

JAVASCRIPTCopied
var pronunciationAssessmentConfig = new window.SpeechSDK.PronunciationAssessmentConfig(
  "My voice is my passport, verify me.",
  window.SpeechSDK.PronunciationAssessmentGradingSystem.HundredMark,
  window.SpeechSDK.PronunciationAssessmentGranularity.Phoneme
);

If you need to assess a different reference text, just change it in the first parameter.

---

2. Use the Correct AudioConfig Input

The sample solution in the documentation demonstrates using a push stream instead of feeding a WAV file directly. While using a WAV file should work, if the service expects a streaming input for pronunciation context, you might get errors. For testing, try switching to a push stream:

JAVASCRIPTCopied
// Example: configuring a push stream input
var pushStream = window.SpeechSDK.AudioInputStream.createPushStream();
var audioConfig = window.SpeechSDK.AudioConfig.fromStreamInput(pushStream);

Then push your WAV file’s data into the stream.

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3. Apply the Pronunciation Assessment Config Once

Make sure you apply the pronunciation assessment configuration to your recognizer only once before starting recognition:

JAVASCRIPTCopied
pronunciationAssessmentConfig.applyTo(speechRecognizer);

A redundant call may not cause issues in every case but can be confusing when troubleshooting.

---

Final Revised Code Example

Below is a sample implementation combining these suggestions:

JAVASCRIPTCopied
assessPronunciation(fileUrl) {
  const speechConfig = window.SpeechSDK.SpeechConfig.fromSubscription("xxx", "westeurope");
  speechConfig.speechRecognitionLanguage = "en-GB";

  // Fetch the WAV file and create a push stream
  fetch(fileUrl)
    .then(response => response.arrayBuffer())
    .then(arrayBuffer => {
      // Create a push stream input and push binary data into it
      var pushStream = window.SpeechSDK.AudioInputStream.createPushStream();
      pushStream.write(arrayBuffer);
      pushStream.close();

      var audioConfig = window.SpeechSDK.AudioConfig.fromStreamInput(pushStream);

      // Use enumerations for grading system and granularity.
      var pronunciationAssessmentConfig = new window.SpeechSDK.PronunciationAssessmentConfig(
        "My voice is my passport, verify me.",
        window.SpeechSDK.PronunciationAssessmentGradingSystem.HundredMark,
        window.SpeechSDK.PronunciationAssessmentGranularity.Phoneme
      );
      
      var speechRecognizer = new window.SpeechSDK.SpeechRecognizer(speechConfig, audioConfig);

      // Apply pronunciation assessment configuration only once.
      pronunciationAssessmentConfig.applyTo(speechRecognizer);

      speechRecognizer.sessionStarted = (s, e) => {
        console.log(`SESSION ID: ${e.sessionId}`);
      };

      speechRecognizer.recognizeOnceAsync(
        function(speechRecognitionResult) {
          if (speechRecognitionResult.reason === window.SpeechSDK.ResultReason.RecognizedSpeech) {
            var pronunciationAssessmentResult = window.SpeechSDK.PronunciationAssessmentResult.fromResult(speechRecognitionResult);
            console.log("pronunciationAssessmentResult", pronunciationAssessmentResult);

            var pronunciationAssessmentResultJson = speechRecognitionResult.properties.getProperty(window.SpeechSDK.PropertyId.SpeechServiceResponse_JsonResult);
            console.log("pronunciationAssessmentResultJson", pronunciationAssessmentResultJson);
          } else {
            console.error("Speech not recognized. Reason:", speechRecognitionResult);
          }
        },
        function(error) {
          console.error("Error during recognition:", error);
          if (error instanceof window.SpeechSDK.SpeechRecognitionCanceledEventArgs) {
            console.error("Recognition canceled. Reason:", error.reason);
            console.error("Error details:", error.errorDetails);
          }
        }
      );
    })
    .catch(error => {
      console.error("Error fetching WAV file:", error);
    });
}

---

Summary

• Use SDK Enumerations: Replace string values with window.SpeechSDK.PronunciationAssessmentGradingSystem.HundredMark and window.SpeechSDK.PronunciationAssessmentGranularity.Phoneme.
• Audio Configuration: Consider using a push stream for the audio, as the sample solution does.
• Single Application of Config: Apply the pronunciation assessment configuration once before recognition.

These changes should help resolve the deserialization error. Happy coding!