Endpointing and latency issue with streaming azure STT

Question

Endpointing and latency issue with streaming azure STT

Hasan Ali 0

Assistance is needed with implementing Azure’s streaming Speech-to-Text. The following issues have been encountered during development:

1. What languages are supported for semantic endpointing in Azure Speech-to-Text? Silence-based endpointing is producing false positives when users pause naturally while speaking. I am Exploring semantic endpointing for this., but available documentation lacks clarity on supported languages.

2. What best practices or configuration adjustments can reduce latency during interim responses in continuous recognition? Significant latency is occurring when receiving interim results during continuous speech recognition, which is negatively affecting real-time user experience.

3. What solutions are recommended to minimize delays when processing single-word utterances in Azure Speech-to-Text? Processing of short, single-word inputs results in noticeable delays, impacting responsiveness and usability in quick-interaction scenarios.

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Answer 1

kothapally Snigdha 2,670 Microsoft External Staff Moderator

Hi @Hasan Ali

Currently, Azure Speech-to-Text supports various languages, but the documentation on semantic end pointing may not specify which ones are applicable. I recommend reviewing the latest Language and voice support for the Speech service to confirm if your target languages are supported for semantic end pointing. To reduce latency, consider the following best practices: Ensure streaming is properly configured in your implementation to provide earlier access to interim results. If possible, batch multiple requests together to significantly improve performance. Avoid mixing different workloads on a single endpoint to prevent delays due to queuing. Check your SDK configuration settings to ensure they are optimized for low latency (such as setting the appropriate output format). Further details are available in the Performance and latency.

Short utterances can be problematic due to the inherent processing time needed to interpret and respond. Stream audio starting from the first received chunk to make the interaction feel more immediate. Consider using the Speech SDK’s capabilities for more efficient buffering and streaming of audio data.

Hope this helps. Do let us know if you any further queries.

If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.

Suwarna S Kale 2,906 Reputation points

2025-05-09T15:29:49.3466667+00:00
Hello Hasan Ali,

Thank you for posting your question in the Microsoft Q&A forum.

1. Supported Languages for Semantic Endpointing - Azure Speech-to-Text's semantic endpointing feature, designed to intelligently detect natural speech pauses rather than relying solely on silence, currently supports a limited set of languages, primarily focusing on English (en-US) with some additional European languages including Spanish (es-ES), French (fr-FR), and German (de-DE). If your application uses an unsupported language, consider:

Adjusting silence-based thresholds (initialSilenceTimeoutMs, endSilenceTimeoutMs) to reduce false positives.

Post-processing logic to filter out unnatural pauses.

Hybrid endpointing (combining silence detection with intent-based pauses via LUIS or OpenAI).

2. Reducing Latency for Interim Results - To minimize latency in Azure Speech-to-Text's continuous recognition, prioritize low-latency network configurations by deploying resources in regions closest to users and enabling WebSocket compression. Adjust recognition parameters like SegmentationSilenceTimeout (300–500ms) to balance responsiveness and accuracy, while opting for the Detailed output format to receive partial results faster. For optimal performance, pre-warm sessions with silent audio and monitor real-time metrics using SpeechSDK logging to identify and address bottlenecks.

To optimize real-time responsiveness:

Use Detailed output format instead of Simple to get faster partial results.

Lower SegmentationSilenceTimeout (e.g., 300ms) to trigger quicker interim updates.

Enable WebSocket compression (EnableCompression) to reduce data transfer delays.

Deploy in a region closest to users (e.g., westus2 for North America) to minimize network latency.

3. Accelerating Single-Word Utterance Processing - To optimize single-word utterance processing in Azure Speech-to-Text, configure the PhraseDetectionTimeout to 0 to prevent unnecessary waiting periods and set a short MaxPhraseDuration (e.g., 1 second) to enforce faster finalization. Additionally, pre-warm the recognition session with a brief silent preamble to mitigate cold-start delays and consider batching requests if real-time constraints persist. These adjustments prioritize speed for short inputs while maintaining accuracy in quick-interaction scenarios.

For short utterances:

Set PhraseDetectionTimeout to 0 to disable waiting for additional input.

Use MaxPhraseDuration (e.g., 1s) to force faster finalization.

Pre-warm the recognition session (send a silent audio preamble) to avoid cold-start delays.

Consider batch processing if real-time latency is unacceptable for single words.

Few additional recommendations:

Test with SpeechSDK Logging to diagnose bottlenecks.

Leverage gRPC streaming (if available) for lower-latency than REST.

File a feature request for expanded semantic endpointing language support.

Some related Microsoft documentation that may help you learn more -

https://learn.microsoft.com/en-us/azure/ai-services/speech-service/

https://learn.microsoft.com/en-us/azure/ai-services/speech-service/language-identification?tabs=once&pivots=programming-language-csharp#use-speech-to-text

If the above answer helped, please do not forget to "Accept Answer" as this may help other community members to refer the info if facing a similar issue. Your contribution to the Microsoft Q&A community is highly appreciated.
kothapally Snigdha 2,670 Reputation points Microsoft External Staff Moderator

2025-05-12T08:53:53.9933333+00:00

Hi @Hasan AliFollowing up to see if the above answer was helpful. If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
Hasan Ali 0 Reputation points

2025-05-12T19:47:26.5433333+00:00

hi @kothapally Snigdha Thank you for your quick response, but none of the provided links are working.
kothapally Snigdha 2,670 Reputation points Microsoft External Staff Moderator

2025-05-13T16:30:30.41+00:00

Hi Hasan Ali

Apologies for the inconvenience. Could you kindly review the updated links provided?

Thank you!
Hasan Ali 0 Reputation points

2025-05-15T12:56:30.8833333+00:00

hi @Suwarna S Kale I am unable to find any parameters like PhraseDetectionTimeout and MaxPhraseDuration, could you please share any documentation containing details about these properties

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Endpointing and latency issue with streaming azure STT

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