Why is speakTextAsync() occasionally silent?

Question

I am using the following Javascript code to test Azure TTS. It works well, but about 1 in 10 times, when called, it produces no sound despite logging "Synthesis finished" as expected. The next time it is called, the sentence "Good morning, how are you doing today?" is played twice.

Are we meant to flush the audio queue somehow?

  speechSynthesizerRef.current = new sdk.SpeechSynthesizer(speechConfig);

try{
    speechSynthesizerRef.current?.speakTextAsync(
      "Good morning, how are you doing today?",
       (result) => {
        if (result.reason === sdk.ResultReason.SynthesizingAudioCompleted) {
          console.log("Synthesis finished.");
        } else {
          console.error(
            "Speech synthesis canceled, " +
              result.errorDetails +
              "\nDid you update the subscription info?"
          );
        }
      },
      (error) => {
        console.log("Speech synthesis Error: ", error);
        speechSynthesizerRef.current?.close();
      }
    );
  } catch (err) {
    console.error("Error synthesizing speech:", err);
    speechSynthesizerRef.current?.close();
  }   

Answer 1

@Praxis Labs Welcome to Microsoft Q&A! Thanks for posting the question.

.

Here are a few suggestions:

1. Enable logging: You could try to enable the verbose debug logs for the speech SDK and check if that logs any error message or exception. In, JavaScript the logging is enabled via SDK diagnostics as shown in the following code snippet:

sdk.Diagnostics.SetLoggingLevel(sdk.LogLevel.Debug);
sdk.Diagnostics.SetLogOutputPath("LogfilePathAndName");

2. Check for Pending Operations: Ensure that there are no pending operations on the SpeechSynthesizer before calling speakTextAsync again. You can do this by checking the state of the synthesizer.
3. Event Handling: Add event listeners for synthesis started, synthesis completed, and synthesis canceled events to better understand the state transitions and catch any anomalies.
4. Dispose of the Synthesizer Properly: Make sure to properly dispose of the SpeechSynthesizer instance when it’s no longer needed. This can help prevent any lingering state issues.
5. Queue Management: If you need to queue audio, consider implementing a custom queue management system that handles the creation and disposal of SpeechSynthesizer instances as needed.

Here’s an example of how you might implement some of these suggestions:

speechSynthesizerRef.current = new sdk.SpeechSynthesizer(speechConfig);

const speakText = (text) => {

  if (speechSynthesizerRef.current) {

    speechSynthesizerRef.current.speakTextAsync(

      text,

      (result) => {

        if (result.reason === sdk.ResultReason.SynthesizingAudioCompleted) {

          console.log("Synthesis finished.");

        } else {

          console.error(

            "Speech synthesis canceled, " +

              result.errorDetails +

              "\nDid you update the subscription info?"

          );

        }

      },

      (error) => {

        console.log("Speech synthesis Error: ", error);

        speechSynthesizerRef.current?.close();

      }

    );

  }

};

const handleSynthesis = async (text) => {

  try {

    if (speechSynthesizerRef.current) {

      // Ensure no pending operations

      await speechSynthesizerRef.current.close();

    }

    speechSynthesizerRef.current = new sdk.SpeechSynthesizer(speechConfig);

    speakText(text);

  } catch (err) {

    console.error("Error synthesizing speech:", err);

    speechSynthesizerRef.current?.close();

  }

};

// Usage

handleSynthesis("Good morning, how are you doing today?");

Hope this helps.