> ## Documentation Index > Fetch the complete documentation index at: https://docs.chariot.in/llms.txt > Use this file to discover all available pages before exploring further. # ASR WebSocket > Streaming speech to text. After the connection opens, the server sends `session.started`. Send audio as binary frames in the declared `audio_format`, as you capture it. The server sends `transcript.delta` events with new text as it is recognized. Send `input.done` after the last frame: the server sends `transcript.done` with the complete transcript and closes with code 1000. Send `keepalive` while you have no audio, so the session is not closed as idle. A session lasts at most `max_duration_seconds` (from `session.started`); `session.expiring` arrives about a minute before the limit. Billing is 1.5 credits per second of audio sent, charged periodically during the session and settled when it closes. Each open session uses one speech-to-text concurrency slot until it closes. Authenticate with the `chariotai-api-key` header, or with the `api_key` query parameter when your client cannot set handshake headers. Terminal errors send an `error` event whose `code` matches the close code that follows: `1008` for an auth problem, an invalid parameter, a product not on your plan, or the idle timeout; `1011` for a server error or a language, mode, or style that cannot be served right now; `4402` for insufficient credits; `4413` when the session reaches its maximum duration; and `4429` for the concurrency limit. An `error` event without a `code` concerns one message, and the session continues. ## AsyncAPI ````yaml api-reference/asyncapi.yaml asrStream id: asrStream title: Speech to text stream description: > Streaming speech to text. After the connection opens, the server sends `session.started`. Send audio as binary frames in the declared `audio_format`, as you capture it. The server sends `transcript.delta` events with new text as it is recognized. Send `input.done` after the last frame: the server sends `transcript.done` with the complete transcript and closes with code 1000. Send `keepalive` while you have no audio, so the session is not closed as idle. A session lasts at most `max_duration_seconds` (from `session.started`); `session.expiring` arrives about a minute before the limit. Billing is 1.5 credits per second of audio sent, charged periodically during the session and settled when it closes. Each open session uses one speech-to-text concurrency slot until it closes. Authenticate with the `chariotai-api-key` header, or with the `api_key` query parameter when your client cannot set handshake headers. Terminal errors send an `error` event whose `code` matches the close code that follows: `1008` for an auth problem, an invalid parameter, a product not on your plan, or the idle timeout; `1011` for a server error or a language, mode, or style that cannot be served right now; `4402` for insufficient credits; `4413` when the session reaches its maximum duration; and `4429` for the concurrency limit. An `error` event without a `code` concerns one message, and the session continues. servers: - id: production protocol: wss host: api.chariot.in bindings: [] variables: [] address: /v1/asr/ws parameters: [] bindings: - protocol: ws version: 0.1.0 value: method: GET query: type: object properties: audio_format: type: string enum: - pcm_8000 - pcm_16000 - pcm_22050 - pcm_24000 - pcm_32000 - pcm_44100 - pcm_48000 - ulaw_8000 - alaw_8000 default: pcm_16000 examples: &ref_0 - pcm_16000 description: > Encoding and sample rate of the audio you send, always mono. `pcm_*` is signed 16-bit little-endian PCM at the named rate. `ulaw_8000` and `alaw_8000` are G.711 telephony audio at 8 kHz. Declare the rate you actually send: audio at another rate is transcribed as the wrong speech, without an error. language: type: string enum: - en - hi - bn - gu - kn - ml - mr - or - pa - sa - ta - te - none examples: &ref_1 - en description: > Language hint for the session. It does not translate. Omit it, or pass `none`, for automatic language detection. mode: type: string enum: - balanced - high_accuracy default: balanced examples: &ref_2 - balanced description: > `balanced` prioritizes responsiveness, for interactive applications. `high_accuracy` allows more context before committing text, which increases latency and usually gives more accurate transcripts. Both cost the same. style: type: string enum: - codemix - native default: codemix examples: &ref_3 - codemix description: > How mixed-language speech is written. `codemix` keeps borrowed words, usually English, in their own script. `native` writes everything in the script of the spoken language. model_type: type: string enum: - chariot-1-asr-realtime default: chariot-1-asr-realtime examples: &ref_4 - chariot-1-asr-realtime description: The speech-to-text model. Default and only value. idle_timeout: type: number default: 60 exclusiveMinimum: 0 maximum: 300 examples: &ref_5 - 60 description: > Seconds the server waits for your next message, audio or JSON, before closing the session as idle with code 1008. Must be greater than 0 and at most 300. api_key: type: string description: > Your API key. Prefer the `chariotai-api-key` header where your client supports it. schemaProperties: - name: method type: string description: GET required: false - name: query type: object required: false properties: - name: audio_format type: string description: > Encoding and sample rate of the audio you send, always mono. `pcm_*` is signed 16-bit little-endian PCM at the named rate. `ulaw_8000` and `alaw_8000` are G.711 telephony audio at 8 kHz. Declare the rate you actually send: audio at another rate is transcribed as the wrong speech, without an error. enumValues: - pcm_8000 - pcm_16000 - pcm_22050 - pcm_24000 - pcm_32000 - pcm_44100 - pcm_48000 - ulaw_8000 - alaw_8000 examples: *ref_0 required: false - name: language type: string description: > Language hint for the session. It does not translate. Omit it, or pass `none`, for automatic language detection. enumValues: - en - hi - bn - gu - kn - ml - mr - or - pa - sa - ta - te - none examples: *ref_1 required: false - name: mode type: string description: > `balanced` prioritizes responsiveness, for interactive applications. `high_accuracy` allows more context before committing text, which increases latency and usually gives more accurate transcripts. Both cost the same. enumValues: - balanced - high_accuracy examples: *ref_2 required: false - name: style type: string description: > How mixed-language speech is written. `codemix` keeps borrowed words, usually English, in their own script. `native` writes everything in the script of the spoken language. enumValues: - codemix - native examples: *ref_3 required: false - name: model_type type: string description: The speech-to-text model. Default and only value. enumValues: - chariot-1-asr-realtime examples: *ref_4 required: false - name: idle_timeout type: number description: > Seconds the server waits for your next message, audio or JSON, before closing the session as idle with code 1008. Must be greater than 0 and at most 300. examples: *ref_5 required: false - name: api_key type: string description: > Your API key. Prefer the `chariotai-api-key` header where your client supports it. required: false operations: - &ref_17 id: sendToChariotAsr title: Client to server description: Audio and messages you send to Chariot. type: receive messages: - &ref_19 id: audio contentType: application/octet-stream payload: - type: string format: binary x-parser-schema-id: name: Audio description: > A binary WebSocket frame of raw audio in the declared `audio_format`. No file header, JSON, or base64. Any frame size works; about 100 ms per frame is a good default. headers: [] jsonPayloadSchema: type: string format: binary x-parser-schema-id: title: Audio description: > A binary WebSocket frame of raw audio in the declared `audio_format`. No file header, JSON, or base64. Any frame size works; about 100 ms per frame is a good default. example: '{}' bindings: [] extensions: - id: x-parser-unique-object-id value: audio - &ref_20 id: keepalive payload: - name: Keep alive description: > Keeps the session open while you have no audio to send. Resets the idle timer. No reply. type: object properties: - name: type type: string description: keepalive required: true headers: [] jsonPayloadSchema: type: object required: - type properties: type: type: string const: keepalive x-parser-schema-id: x-parser-schema-id: title: Keep alive description: > Keeps the session open while you have no audio to send. Resets the idle timer. No reply. example: |- { "type": "" } bindings: [] extensions: - id: x-parser-unique-object-id value: keepalive - &ref_21 id: inputDone payload: - name: End input description: > No more audio is coming. The server transcribes the rest, sends `transcript.done`, and closes with code 1000. Audio sent afterwards is not transcribed. type: object properties: - name: type type: string description: input.done required: true headers: [] jsonPayloadSchema: type: object required: - type properties: type: type: string const: input.done x-parser-schema-id: x-parser-schema-id: title: End input description: > No more audio is coming. The server transcribes the rest, sends `transcript.done`, and closes with code 1000. Audio sent afterwards is not transcribed. example: |- { "type": "" } bindings: [] extensions: - id: x-parser-unique-object-id value: inputDone bindings: [] extensions: &ref_16 - id: x-parser-unique-object-id value: asrStream - &ref_18 id: receiveFromChariotAsr title: Server to client description: Events Chariot sends back to you. type: send messages: - &ref_22 id: sessionStarted payload: - name: Session started description: >- The session is ready for audio. Sent once, first, with the settings in effect. type: object properties: - name: type type: string description: session.started required: false - name: session_id type: string description: >- Unique id for the session. Use it with `GET /v1/asr/sessions/{session_id}`. required: false - name: model_type type: string examples: &ref_6 - chariot-1-asr-realtime required: false - name: sample_rate type: integer description: Sample rate of the declared audio format, in Hz. examples: &ref_7 - 16000 required: false - name: language type: &ref_8 - string - 'null' description: The language hint, or null for automatic language detection. required: false - name: mode type: string enumValues: - balanced - high_accuracy required: false - name: style type: string enumValues: - codemix - native required: false - name: audio_format type: string examples: &ref_9 - pcm_16000 required: false - name: max_duration_seconds type: integer description: The longest this session can run, in seconds. examples: &ref_10 - 10800 required: false headers: [] jsonPayloadSchema: type: object properties: type: type: string const: session.started x-parser-schema-id: session_id: type: string format: uuid description: >- Unique id for the session. Use it with `GET /v1/asr/sessions/{session_id}`. x-parser-schema-id: model_type: type: string examples: *ref_6 x-parser-schema-id: sample_rate: type: integer description: Sample rate of the declared audio format, in Hz. examples: *ref_7 x-parser-schema-id: language: type: *ref_8 description: The language hint, or null for automatic language detection. x-parser-schema-id: mode: type: string enum: - balanced - high_accuracy x-parser-schema-id: style: type: string enum: - codemix - native x-parser-schema-id: audio_format: type: string examples: *ref_9 x-parser-schema-id: max_duration_seconds: type: integer description: The longest this session can run, in seconds. examples: *ref_10 x-parser-schema-id: x-parser-schema-id: title: Session started description: >- The session is ready for audio. Sent once, first, with the settings in effect. example: |- { "type": "", "session_id": "", "model_type": "", "sample_rate": 123, "mode": "", "style": "", "audio_format": "", "max_duration_seconds": 123 } bindings: [] extensions: - id: x-parser-unique-object-id value: sessionStarted - &ref_23 id: transcriptDelta payload: - name: Transcript delta description: > New text, as it is recognized. Append it to the text so far; spaces are included. Use `transcript.done` for the final text. type: object properties: - name: type type: string description: transcript.delta required: false - name: text type: string examples: &ref_11 - ' the meeting' required: false headers: [] jsonPayloadSchema: type: object properties: type: type: string const: transcript.delta x-parser-schema-id: text: type: string examples: *ref_11 x-parser-schema-id: x-parser-schema-id: title: Transcript delta description: > New text, as it is recognized. Append it to the text so far; spaces are included. Use `transcript.done` for the final text. example: |- { "type": "", "text": "" } bindings: [] extensions: - id: x-parser-unique-object-id value: transcriptDelta - &ref_24 id: transcriptDone payload: - name: Transcript done description: > The complete transcript, sent once after `input.done`. The connection then closes with code 1000. type: object properties: - name: type type: string description: transcript.done required: false - name: text type: string examples: &ref_12 - Hi, I'd like to move the meeting to Thursday. required: false - name: audio_seconds type: number description: Duration of the audio you sent, in seconds. examples: &ref_13 - 4.82 required: false headers: [] jsonPayloadSchema: type: object properties: type: type: string const: transcript.done x-parser-schema-id: text: type: string examples: *ref_12 x-parser-schema-id: audio_seconds: type: number description: Duration of the audio you sent, in seconds. examples: *ref_13 x-parser-schema-id: x-parser-schema-id: title: Transcript done description: > The complete transcript, sent once after `input.done`. The connection then closes with code 1000. example: |- { "type": "", "text": "", "audio_seconds": 123 } bindings: [] extensions: - id: x-parser-unique-object-id value: transcriptDone - &ref_25 id: sessionExpiring payload: - name: Session expiring description: > The session reaches `max_duration_seconds` soon. Sent once, about a minute before the limit. At the limit the session closes with 4413. type: object properties: - name: type type: string description: session.expiring required: false - name: seconds_remaining type: integer examples: &ref_14 - 52 required: false headers: [] jsonPayloadSchema: type: object properties: type: type: string const: session.expiring x-parser-schema-id: seconds_remaining: type: integer examples: *ref_14 x-parser-schema-id: x-parser-schema-id: title: Session expiring description: > The session reaches `max_duration_seconds` soon. Sent once, about a minute before the limit. At the limit the session closes with 4413. example: |- { "type": "", "seconds_remaining": 123 } bindings: [] extensions: - id: x-parser-unique-object-id value: sessionExpiring - &ref_26 id: errorMessage payload: - name: Error description: > An error. With a `code`, it is terminal and the connection closes with that code. Without a `code`, it concerns one message (invalid JSON or an unknown message type) and the session continues. type: object properties: - name: type type: string description: error required: false - name: code type: integer description: The close code that follows. Absent for nonterminal errors. enumValues: - 1008 - 1011 - 4402 - 4413 - 4429 required: false - name: message type: string examples: &ref_15 - Insufficient credits required: false headers: [] jsonPayloadSchema: type: object properties: type: type: string const: error x-parser-schema-id: code: type: integer enum: - 1008 - 1011 - 4402 - 4413 - 4429 description: The close code that follows. Absent for nonterminal errors. x-parser-schema-id: message: type: string examples: *ref_15 x-parser-schema-id: x-parser-schema-id: title: Error description: > An error. With a `code`, it is terminal and the connection closes with that code. Without a `code`, it concerns one message (invalid JSON or an unknown message type) and the session continues. example: |- { "type": "", "code": 123, "message": "" } bindings: [] extensions: - id: x-parser-unique-object-id value: errorMessage bindings: [] extensions: *ref_16 sendOperations: - *ref_17 receiveOperations: - *ref_18 sendMessages: - *ref_19 - *ref_20 - *ref_21 receiveMessages: - *ref_22 - *ref_23 - *ref_24 - *ref_25 - *ref_26 extensions: - id: x-parser-unique-object-id value: asrStream securitySchemes: [] ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.