6.2.1. Speech-to-Text (STT)

🔧 Implementation Reference: Speech-to-Text

Testable Pattern:

import azure.cognitiveservices.speech as speechsdk

speech_config = speechsdk.SpeechConfig(subscription=key, region=region)
recognizer = speechsdk.SpeechRecognizer(speech_config=speech_config, audio_config=audio_config)
result = recognizer.recognize_once()
text = result.text

Error Handling Pattern:

import azure.cognitiveservices.speech as speechsdk

def transcribe_with_error_handling(audio_file: str) -> str:
    """Speech-to-text with comprehensive error handling."""
    speech_config = speechsdk.SpeechConfig(subscription=key, region=region)
    audio_config = speechsdk.AudioConfig(filename=audio_file)
    recognizer = speechsdk.SpeechRecognizer(speech_config=speech_config, audio_config=audio_config)
    
    result = recognizer.recognize_once()
    
    if result.reason == speechsdk.ResultReason.RecognizedSpeech:
        return result.text
    elif result.reason == speechsdk.ResultReason.NoMatch:
        # Audio was processed but no speech detected
        no_match_detail = result.no_match_details
        logging.warning(f"No speech recognized: {no_match_detail.reason}")
        return ""
    elif result.reason == speechsdk.ResultReason.Canceled:
        cancellation = result.cancellation_details
        if cancellation.reason == speechsdk.CancellationReason.Error:
            logging.error(f"Speech error: {cancellation.error_code} - {cancellation.error_details}")
            if cancellation.error_code == speechsdk.CancellationErrorCode.ConnectionFailure:
                raise ConnectionError("Speech service connection failed")
            elif cancellation.error_code == speechsdk.CancellationErrorCode.AuthenticationFailure:
                raise PermissionError("Invalid speech subscription key or region")
        return ""

CLI Equivalent (REST):

curl -X POST "https://{region}.stt.speech.microsoft.com/speech/recognition/conversation/cognitiveservices/v1?language=en-US" \
  -H "Ocp-Apim-Subscription-Key: {key}" \
  -H "Content-Type: audio/wav" \
  --data-binary @audio.wav

⚠️ Exam Trap: Check result.reason for speech operations—NoMatch means audio was processed but no speech detected; Canceled with ErrorCode indicates a service error.