> ## Documentation Index > Fetch the complete documentation index at: https://developers.telnyx.com/llms.txt > Use this file to discover all available pages before exploring further. # Stream speech to text over WebSocket > AsyncAPI specification for the Telnyx Speech-to-Text WebSocket endpoint. Real-time speech transcription by streaming audio and receiving transcript frames. ## Supported Engines - `Azure` - Microsoft Azure Speech Services - `Deepgram` - Deepgram Nova models - `Google` - Google Cloud Speech-to-Text - `Telnyx` - Telnyx native transcription (OpenAI Whisper models) - `xAI` - xAI Grok STT - `AssemblyAI` - AssemblyAI Universal-Streaming ## Connection Flow 1. Open WebSocket connection to `wss://api.telnyx.com/v2/speech-to-text/transcription` with query parameters. 2. Send binary audio frames (mp3 or wav format). 3. Receive JSON transcript frames with `transcript`, `is_final`, and `confidence` fields. 4. Close connection when done. ## Authentication Requires authentication via a Bearer token (Telnyx API v2 key). ## AsyncAPI ````yaml https://telnyx-openapi-ng.s3.us-east-1.amazonaws.com/speech-to-text-websockets/speech-to-text-websockets.yml speech-to-text-websockets id: speech-to-text-websockets title: Stream speech to text over WebSocket description: > AsyncAPI specification for the Telnyx Speech-to-Text WebSocket endpoint. Real-time speech transcription by streaming audio and receiving transcript frames. ## Supported Engines - `Azure` - Microsoft Azure Speech Services - `Deepgram` - Deepgram Nova models - `Google` - Google Cloud Speech-to-Text - `Telnyx` - Telnyx native transcription (OpenAI Whisper models) - `xAI` - xAI Grok STT - `AssemblyAI` - AssemblyAI Universal-Streaming ## Connection Flow 1. Open WebSocket connection to `wss://api.telnyx.com/v2/speech-to-text/transcription` with query parameters. 2. Send binary audio frames (mp3 or wav format). 3. Receive JSON transcript frames with `transcript`, `is_final`, and `confidence` fields. 4. Close connection when done. ## Authentication Requires authentication via a Bearer token (Telnyx API v2 key). servers: - id: speech-to-text-websockets protocol: wss host: api.telnyx.com bindings: - protocol: ws version: 0.1.0 value: {} schemaProperties: [] variables: [] address: /v2/speech-to-text/transcription parameters: [] bindings: - protocol: ws version: 0.1.0 value: query: type: object description: Query parameters passed when opening the WebSocket connection. required: - transcription_engine - input_format properties: transcription_engine: type: string description: The transcription engine to use for processing the audio stream. enum: - Azure - Deepgram - Google - Telnyx - xAI - AssemblyAI input_format: type: string description: The format of input audio stream. enum: - mp3 - wav language: type: string description: | The language spoken in the audio stream (e.g., en-US, es-ES). interim_results: type: boolean description: >- Whether to receive interim transcription results before final results. default: false model: type: string description: > The specific model to use within the selected transcription engine. Available models vary by engine: - Azure: `fast` - Deepgram: `deepgram/nova-2`, `deepgram/nova-3` - Google: `latest_long`, `latest_short`, `command_and_search`, `phone_call`, `video`, `default`, `medical_conversation`, `medical_dictation` - Telnyx: `openai/whisper-tiny`, `openai/whisper-large-v3-turbo` - xAI: `xai/grok-stt` - AssemblyAI: `assemblyai/universal-streaming` endpointing: type: integer description: > Silence duration (in milliseconds) that triggers end-of-speech detection. When set, the engine uses this value to determine when a speaker has stopped talking. Supported by xAI, Deepgram, and Google. Other engines may not support this parameter. redact: type: string description: > Enable redaction of sensitive information (e.g., PCI data, SSN) from transcription results. Supported values depend on the transcription engine. keyterm: type: string description: | A key term to boost in the transcription. The engine will be more likely to recognize this term. Can be specified multiple times for multiple terms. keywords: type: string description: | Comma-separated list of keywords to boost in the transcription. The engine will prioritize recognition of these words. schemaProperties: - name: query type: object description: Query parameters passed when opening the WebSocket connection. required: false properties: - name: transcription_engine type: string description: The transcription engine to use for processing the audio stream. enumValues: - Azure - Deepgram - Google - Telnyx - xAI - AssemblyAI required: false - name: input_format type: string description: The format of input audio stream. enumValues: - mp3 - wav required: false - name: language type: string description: | The language spoken in the audio stream (e.g., en-US, es-ES). required: false - name: interim_results type: boolean description: >- Whether to receive interim transcription results before final results. required: false - name: model type: string description: > The specific model to use within the selected transcription engine. Available models vary by engine: - Azure: `fast` - Deepgram: `deepgram/nova-2`, `deepgram/nova-3` - Google: `latest_long`, `latest_short`, `command_and_search`, `phone_call`, `video`, `default`, `medical_conversation`, `medical_dictation` - Telnyx: `openai/whisper-tiny`, `openai/whisper-large-v3-turbo` - xAI: `xai/grok-stt` - AssemblyAI: `assemblyai/universal-streaming` required: false - name: endpointing type: integer description: > Silence duration (in milliseconds) that triggers end-of-speech detection. When set, the engine uses this value to determine when a speaker has stopped talking. Supported by xAI, Deepgram, and Google. Other engines may not support this parameter. required: false - name: redact type: string description: > Enable redaction of sensitive information (e.g., PCI data, SSN) from transcription results. Supported values depend on the transcription engine. required: false - name: keyterm type: string description: | A key term to boost in the transcription. The engine will be more likely to recognize this term. Can be specified multiple times for multiple terms. required: false - name: keywords type: string description: | Comma-separated list of keywords to boost in the transcription. The engine will prioritize recognition of these words. required: false operations: - &ref_1 id: sendAudio title: Send Audio to Transcribe description: Client sends binary audio frames to be transcribed into text. type: receive messages: - &ref_3 id: clientAudio contentType: application/octet-stream payload: - type: string format: binary description: > Client-to-server binary frame containing audio data to transcribe. Audio should be in mp3 or wav format as specified in the input_format query parameter. x-parser-schema-id: name: Audio Frame headers: [] jsonPayloadSchema: type: string format: binary description: Binary audio data in mp3 or wav format. x-parser-schema-id: title: Audio Frame description: > Client-to-server binary frame containing audio data to transcribe. Audio should be in mp3 or wav format as specified in the input_format query parameter. example: '{}' bindings: [] extensions: - id: x-parser-unique-object-id value: clientAudio bindings: [] extensions: &ref_0 - id: x-parser-unique-object-id value: speech-to-text-websockets - &ref_2 id: receiveTranscript title: Receive Transcript Frames description: Server sends transcript frames and error frames to the client. type: send messages: - &ref_4 id: serverTranscript contentType: application/json payload: - name: Transcript Frame description: > Server-to-client frame containing a transcription result. When interim_results is enabled, you may receive multiple interim results (is_final=false) before the final result (is_final=true) for each utterance. type: object properties: - name: type type: string description: Frame type identifier. required: true - name: transcript type: string description: The transcribed text from the audio. required: true - name: is_final type: boolean description: | Whether this is a final transcription result. When false, this is an interim result that may be refined. required: false - name: confidence type: number description: Confidence score of the transcription, ranging from 0 to 1. required: false headers: [] jsonPayloadSchema: type: object required: - type - transcript properties: type: type: string const: transcript description: Frame type identifier. x-parser-schema-id: transcript: type: string description: The transcribed text from the audio. x-parser-schema-id: is_final: type: boolean description: | Whether this is a final transcription result. When false, this is an interim result that may be refined. x-parser-schema-id: confidence: type: number description: Confidence score of the transcription, ranging from 0 to 1. minimum: 0 maximum: 1 x-parser-schema-id: x-parser-schema-id: title: Transcript Frame description: > Server-to-client frame containing a transcription result. When interim_results is enabled, you may receive multiple interim results (is_final=false) before the final result (is_final=true) for each utterance. example: |- { "type": "transcript", "transcript": "Hello, this is", "is_final": false, "confidence": 0.85 } bindings: [] extensions: - id: x-parser-unique-object-id value: serverTranscript - &ref_5 id: serverError contentType: application/json payload: - name: Error Frame description: | Server-to-client frame indicating an error during transcription. The connection may be closed shortly after sending this frame. type: object properties: - name: type type: string description: Frame type identifier. required: true - name: error type: string description: Error message describing what went wrong. required: true headers: [] jsonPayloadSchema: type: object required: - type - error properties: type: type: string const: error description: Frame type identifier. x-parser-schema-id: error: type: string description: Error message describing what went wrong. x-parser-schema-id: x-parser-schema-id: title: Error Frame description: | Server-to-client frame indicating an error during transcription. The connection may be closed shortly after sending this frame. example: |- { "type": "error", "error": "Invalid transcription_engine specified" } bindings: [] extensions: - id: x-parser-unique-object-id value: serverError bindings: [] extensions: *ref_0 sendOperations: - *ref_1 receiveOperations: - *ref_2 sendMessages: - *ref_3 receiveMessages: - *ref_4 - *ref_5 extensions: - id: x-parser-unique-object-id value: speech-to-text-websockets securitySchemes: - id: bearerAuth name: bearerAuth type: http description: Telnyx API v2 Bearer token authentication. scheme: bearer extensions: [] ````