About Speech to Text API

The Speech to Text API transcribes audio streams into text that your application can display to the user or act upon as command input. The APIs can be used either with an SDK client library (for supported platforms and languages) or a REST API.

The Speech to Text API offers the following features:

  • Advanced speech recognition technology from Microsoft—the same used by Cortana, Office, and other Microsoft products.

  • Real-time continuous recognition. Speech to Text allows users to transcribe audio into text in real time. It also supports receiving intermediate results of the words that have been recognized so far. The service automatically recognizes the end of speech. Users can also choose additional formatting options, including capitalization and punctuation, profanity masking, and text normalization.

  • Optimized Speech to Text results for interactive, conversation, and dictation scenarios.

  • Support for many spoken languages in multiple dialects. For the full list of supported languages in each recognition mode, see Supported languages.

  • Customized language and acoustic models, so you can tailor your application to your users' way of speaking, speaking environment, and specialized vocabulary.

  • Natural-language understanding. Through integration with Language Understanding (LUIS), you can derive intents and entities from speech. Users don't have to know your app's vocabulary, but can describe what they want in their own words.

API capabilities

Some capabilities of the Speech to Text API are not available via REST. The following table summarizes the capabilities of each method of accessing the API.

Use case REST SDKs
Transcribe a short utterance, such as a command (length < 15 s); no interim results Yes Yes
Transcribe a longer utterance (> 15 s) No Yes
Transcribe streaming audio with optional interim results No Yes
Understand speaker intents via LUIS No* Yes

* LUIS intents and entities can be derived using a separate LUIS subscription. With this subscription, the SDK can call LUIS for you and provide entity and intent results as well as speech transcriptions. With the REST API, you can call LUIS yourself to derive intents and entities with your LUIS subscription.

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