> ## Documentation Index > Fetch the complete documentation index at: https://docs.slng.ai/llms.txt > Use this file to discover all available pages before exploring further. # Nova 3 (English) > Stream real-time English transcripts from SLNG-hosted Deepgram Nova 3 over WebSocket with low-latency partials, finals, and speaker diarization. ## AsyncAPI ````yaml api-reference/asyncapi/stt-slng.asyncapi.yaml /v1/stt/slng/deepgram/nova:3-en id: /v1/stt/slng/deepgram/nova:3-en title: Nova 3 (English) description: >- Stream real-time English transcripts from SLNG-hosted Deepgram Nova 3 over WebSocket with low-latency partials, finals, and speaker diarization. servers: - id: production protocol: wss host: api.slng.ai bindings: [] variables: [] address: /v1/stt/slng/deepgram/nova:3-en parameters: [] bindings: - protocol: ws version: latest value: method: GET headers: type: object properties: X-Region-Override: type: string description: >- Target region override. Auto-selected if not provided. Available regions: `asia-south1`, `australia-southeast1`, `us-east-1`. enum: - asia-south1 - australia-southeast1 - us-east-1 x-parser-schema-id: x-parser-schema-id: WebsocketHeadersSlngNovaEn schemaProperties: - name: method type: string description: GET required: false - name: headers type: object required: false properties: - name: X-Region-Override type: string description: >- Target region override. Auto-selected if not provided. Available regions: `asia-south1`, `australia-southeast1`, `us-east-1`. enumValues: - asia-south1 - australia-southeast1 - us-east-1 required: false operations: - &ref_1 id: sttSlngDeepgramNova3EnReceiveInit title: Stt slng deepgram nova3 en receive init description: Initialize session on Deepgram Nova 3 (English) type: receive messages: - &ref_9 id: SlngDeepgramNova3EnSttInitRequest contentType: application/json payload: - name: Init Request description: Initialize an SLNG-hosted Deepgram Nova 3 English STT session. type: object properties: - name: type type: string description: init required: true - name: config type: object description: Recognition configuration options required: false properties: - name: language type: string description: Supported English language code. enumValues: - en - en-au - en-us - en-nz - en-gb - en-in required: false - name: sample_rate type: integer description: Input audio sample rate in Hz. required: false - name: encoding type: string description: Input audio encoding format. enumValues: - linear16 - flac - mulaw - amr-nb - amr-wb - opus - speex - mp3 - mp4 - webm - aac - ogg required: false - name: enable_partials type: boolean description: Enable partial/interim transcription results. required: false - name: punctuate type: boolean description: Add punctuation and capitalization. required: false - name: smart_format type: boolean description: >- Apply formatting to improve readability (dates, times, numbers, etc.). required: false - name: diarize type: boolean description: >- Enable speaker diarization. Words assigned speaker numbers starting at 0. required: false - name: numerals type: boolean description: Convert spoken numbers to digits. required: false - name: profanity_filter type: boolean description: Filter profanity from transcript. required: false - name: utterances type: boolean description: Segment transcript into utterances. required: false - name: paragraphs type: boolean description: Add paragraph formatting. required: false - name: filler_words type: boolean description: Include filler words (uh, um) in transcript. required: false - name: multichannel type: boolean description: Enable multi-channel audio processing. required: false - name: endpointing type: integer description: >- Time in milliseconds of silence before finalizing speech. Set to 0 to disable endpointing entirely. required: false - name: utterance_end_ms type: integer description: >- Time in milliseconds of silence between words before sending an UtteranceEnd message. Default is 1000ms, minimum 200ms, maximum 5000ms. Requires enable_partials to be true. required: false headers: [] jsonPayloadSchema: type: object required: - type properties: type: type: string const: init x-parser-schema-id: config: type: object description: Recognition configuration options properties: language: type: string description: Supported English language code. default: en enum: - en - en-au - en-us - en-nz - en-gb - en-in x-parser-schema-id: sample_rate: type: integer description: Input audio sample rate in Hz. default: 16000 x-parser-schema-id: encoding: type: string description: Input audio encoding format. default: linear16 enum: - linear16 - flac - mulaw - amr-nb - amr-wb - opus - speex - mp3 - mp4 - webm - aac - ogg x-parser-schema-id: enable_partials: type: boolean description: Enable partial/interim transcription results. default: true x-parser-schema-id: punctuate: type: boolean description: Add punctuation and capitalization. default: false x-parser-schema-id: smart_format: type: boolean description: >- Apply formatting to improve readability (dates, times, numbers, etc.). default: false x-parser-schema-id: diarize: type: boolean description: >- Enable speaker diarization. Words assigned speaker numbers starting at 0. default: false x-parser-schema-id: numerals: type: boolean description: Convert spoken numbers to digits. default: false x-parser-schema-id: profanity_filter: type: boolean description: Filter profanity from transcript. default: false x-parser-schema-id: utterances: type: boolean description: Segment transcript into utterances. default: false x-parser-schema-id: paragraphs: type: boolean description: Add paragraph formatting. default: false x-parser-schema-id: filler_words: type: boolean description: Include filler words (uh, um) in transcript. default: false x-parser-schema-id: multichannel: type: boolean description: Enable multi-channel audio processing. default: false x-parser-schema-id: endpointing: type: integer minimum: 0 default: 10 description: >- Time in milliseconds of silence before finalizing speech. Set to 0 to disable endpointing entirely. x-parser-schema-id: utterance_end_ms: type: integer minimum: 200 maximum: 5000 default: 1000 description: >- Time in milliseconds of silence between words before sending an UtteranceEnd message. Default is 1000ms, minimum 200ms, maximum 5000ms. Requires enable_partials to be true. x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: SlngDeepgramNova3EnSttInitPayload title: Init Request description: Initialize an SLNG-hosted Deepgram Nova 3 English STT session. example: |- { "type": "init", "config": { "language": "en", "sample_rate": 16000, "encoding": "linear16", "enable_partials": true, "smart_format": true, "utterances": true } } bindings: [] extensions: - id: x-parser-unique-object-id value: SlngDeepgramNova3EnSttInitRequest bindings: [] extensions: &ref_0 - id: x-parser-unique-object-id value: /v1/stt/slng/deepgram/nova:3-en - &ref_2 id: sttSlngDeepgramNova3EnReceiveAudio title: Stt slng deepgram nova3 en receive audio description: Send audio frame to Deepgram Nova 3 (English) type: receive messages: - &ref_10 id: DeepgramSttBinaryAudio contentType: application/octet-stream payload: - type: string format: binary description: > Stream raw binary PCM audio frames to be transcribed. Sent as binary WebSocket frames (NOT JSON). Recommended chunk size is 8192 bytes (~256ms at 16kHz linear16). Start streaming immediately after the init message — do not wait for the Metadata response. x-parser-schema-id: name: Binary Audio Frame headers: [] jsonPayloadSchema: type: string format: binary description: > Raw binary audio data (linear16 PCM at 16kHz mono). Sent as a binary WebSocket frame — no JSON envelope, no base64 encoding. Each frame is a chunk of raw PCM samples. Example hex dump of one frame (speech waveform): 0000FF00000000FF00000000010101010101010100000000FFFFFFFEFE FEFEFDFEFEFEFEFDFDFEFEFEFEFEFEFEFEFEFFFFFFFFFEFEFEFEFF000100 001020303030303030303030201010000FFFFFEFDFDFDFDFEFFFFFFFF00 Each pair of hex digits is one byte. At 16kHz linear16, 8192 bytes = 4096 samples = ~256ms of audio. x-parser-schema-id: title: Binary Audio Frame description: > Stream raw binary PCM audio frames to be transcribed. Sent as binary WebSocket frames (NOT JSON). Recommended chunk size is 8192 bytes (~256ms at 16kHz linear16). Start streaming immediately after the init message — do not wait for the Metadata response. example: >- "0000FF00000000FF00000000010101010101010100000000FFFFFFFFFFFFFEFEFDFEFEFEFEFDFDFEFEFEFEFEFEFEFEFEFFFFFFFFFEFEFEFEFF000100001020303030303030303030201010000FFFFFEFDFDFDFDFEFFFFFFFF0001020303020201000000FFFDFCFBFAFAFBFAF9F8F7F7F7F6F6F4F2F2F3F7FC000406090F14191A19181715110E0A05FEF9F6F3F0EEECEBEBECEEF2F6F9FC0005090D0F101010100E0C080401" bindings: [] extensions: - id: x-parser-unique-object-id value: DeepgramSttBinaryAudio bindings: [] extensions: *ref_0 - &ref_3 id: sttSlngDeepgramNova3EnReceiveFinalize title: Stt slng deepgram nova3 en receive finalize description: Force-finalize buffered audio on Deepgram Nova 3 (English) type: receive messages: - &ref_11 id: SttFinalizeMessage contentType: application/json payload: - name: Finalize Message description: >- Force-finalize buffered audio tokens without closing the connection. type: object properties: - name: type type: string description: finalize required: true headers: [] jsonPayloadSchema: type: object description: >- Mid-stream flush — forces the server to finalize any buffered audio and return results. The connection remains open for further audio. required: - type properties: type: type: string const: finalize x-parser-schema-id: x-parser-schema-id: title: Finalize Message description: Force-finalize buffered audio tokens without closing the connection. example: |- { "type": "finalize" } bindings: [] extensions: - id: x-parser-unique-object-id value: SttFinalizeMessage bindings: [] extensions: *ref_0 - &ref_4 id: sttSlngDeepgramNova3EnReceiveClose title: Stt slng deepgram nova3 en receive close description: Close audio stream on Deepgram Nova 3 (English) type: receive messages: - &ref_12 id: SttCloseMessage contentType: application/json payload: - name: Close Message description: Signal end of audio stream and close the connection. type: object properties: - name: type type: string description: close required: true headers: [] jsonPayloadSchema: type: object description: >- Signal that no more audio will be sent. The server processes remaining audio, sends final results, then closes the connection. required: - type properties: type: type: string const: close x-parser-schema-id: x-parser-schema-id: title: Close Message description: Signal end of audio stream and close the connection. example: |- { "type": "close" } bindings: [] extensions: - id: x-parser-unique-object-id value: SttCloseMessage bindings: [] extensions: *ref_0 - &ref_5 id: sttSlngDeepgramNova3EnReceiveKeepalive title: Stt slng deepgram nova3 en receive keepalive description: Send keepalive on Deepgram Nova 3 (English) type: receive messages: - &ref_13 id: KeepaliveMessage contentType: application/json payload: - name: Keepalive Message description: Keep the WebSocket connection alive during silence. type: object properties: - name: type type: string description: keepalive required: true headers: [] jsonPayloadSchema: type: object description: >- Prevents the connection from being closed due to inactivity. Send periodically during silence to maintain the session. required: - type properties: type: type: string const: keepalive x-parser-schema-id: x-parser-schema-id: title: Keepalive Message description: Keep the WebSocket connection alive during silence. example: |- { "type": "keepalive" } bindings: [] extensions: - id: x-parser-unique-object-id value: KeepaliveMessage bindings: [] extensions: *ref_0 - &ref_6 id: sttSlngDeepgramNova3EnSendMetadata title: Stt slng deepgram nova3 en send metadata description: Receive Deepgram session metadata from Nova 3 (English) type: send messages: - &ref_14 id: DeepgramSttMetadata contentType: application/json payload: - name: Metadata description: > Deepgram session metadata. Sent when the backend connects and again after the session ends with final statistics. This is informational — do not wait for it before streaming audio. type: object properties: - name: type type: string description: Metadata required: true - name: request_id type: string description: Unique Deepgram request identifier required: false - name: created type: string description: Timestamp when the session was created required: false - name: duration type: number description: >- Total audio duration processed in seconds (0 on initial, populated on final) required: false - name: channels type: integer description: Number of audio channels required: false - name: sha256 type: string description: SHA-256 hash of the audio (populated on final Metadata only) required: false - name: transaction_key type: string description: Deprecated field (always "deprecated") required: false headers: [] jsonPayloadSchema: type: object description: > Deepgram native Metadata message. Received twice: once when the session opens (duration=0) and once after finalize with the full session summary. required: - type properties: type: type: string const: Metadata x-parser-schema-id: request_id: type: string description: Unique Deepgram request identifier x-parser-schema-id: created: type: string format: date-time description: Timestamp when the session was created x-parser-schema-id: duration: type: number description: >- Total audio duration processed in seconds (0 on initial, populated on final) x-parser-schema-id: channels: type: integer description: Number of audio channels x-parser-schema-id: sha256: type: string description: SHA-256 hash of the audio (populated on final Metadata only) x-parser-schema-id: transaction_key: type: string description: Deprecated field (always "deprecated") x-parser-schema-id: x-parser-schema-id: title: Metadata description: > Deepgram session metadata. Sent when the backend connects and again after the session ends with final statistics. This is informational — do not wait for it before streaming audio. example: |- { "type": "Metadata", "request_id": "a2b1db35-40ff-41f9-9912-dedaeab02228", "created": "2026-04-01T09:40:09.152Z", "duration": 0, "channels": 1, "sha256": "incomplete", "transaction_key": "deprecated" } bindings: [] extensions: - id: x-parser-unique-object-id value: DeepgramSttMetadata bindings: [] extensions: *ref_0 - &ref_7 id: sttSlngDeepgramNova3EnSendResults title: Stt slng deepgram nova3 en send results description: Receive transcription results from Deepgram Nova 3 (English) type: send messages: - &ref_15 id: DeepgramSttResultsEn contentType: application/json payload: - name: Results description: >- Deepgram transcription result — partial or final, determined by is_final. type: object properties: - name: type type: string description: Results required: true - name: is_final type: boolean description: true for final results, false for interim/partial required: false - name: speech_final type: boolean description: true when endpoint detection fires (end of utterance) required: false - name: channel_index type: array description: Channel index pair [channel, total_channels] required: false properties: - name: item type: integer required: false - name: channel type: object description: Deepgram channel result with transcription alternatives required: true properties: - name: alternatives type: array required: false properties: - name: transcript type: string description: Transcribed text required: false - name: confidence type: number description: Confidence score (0-1) required: false - name: words type: array description: Word-level transcription details required: false properties: - name: word type: string required: false - name: start type: number description: Word start time in seconds required: false - name: end type: number description: Word end time in seconds required: false - name: confidence type: number required: false - name: speaker type: integer description: Speaker ID (when diarization enabled) required: false - name: punctuated_word type: string required: false - name: start type: number description: Start time of this segment in seconds required: false - name: duration type: number description: Duration of this segment in seconds required: false headers: [] jsonPayloadSchema: type: object description: > Deepgram native Results message. Contains the transcription in channel.alternatives[0].transcript. Use is_final to distinguish partial (interim) from final results, and speech_final to detect end-of-utterance boundaries. required: - type - channel properties: type: type: string const: Results x-parser-schema-id: is_final: type: boolean description: true for final results, false for interim/partial x-parser-schema-id: speech_final: type: boolean description: true when endpoint detection fires (end of utterance) x-parser-schema-id: channel_index: type: array items: type: integer x-parser-schema-id: description: Channel index pair [channel, total_channels] x-parser-schema-id: channel: type: object description: Deepgram channel result with transcription alternatives properties: alternatives: type: array items: type: object properties: transcript: type: string description: Transcribed text x-parser-schema-id: confidence: type: number description: Confidence score (0-1) x-parser-schema-id: words: type: array description: Word-level transcription details items: type: object properties: word: type: string x-parser-schema-id: start: type: number description: Word start time in seconds x-parser-schema-id: end: type: number description: Word end time in seconds x-parser-schema-id: confidence: type: number x-parser-schema-id: speaker: type: integer description: Speaker ID (when diarization enabled) x-parser-schema-id: punctuated_word: type: string x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: start: type: number description: Start time of this segment in seconds x-parser-schema-id: duration: type: number description: Duration of this segment in seconds x-parser-schema-id: x-parser-schema-id: DeepgramSttResultsPayload title: Results description: >- Deepgram transcription result — partial or final, determined by is_final. example: |- { "type": "Results", "channel_index": [ 0, 1 ], "duration": 3.52, "start": 0, "is_final": true, "speech_final": true, "channel": { "alternatives": [ { "transcript": "The quick brown fox jumps over the lazy dog.", "confidence": 0.9980469, "words": [ { "word": "the", "start": 0.08, "end": 0.16, "confidence": 0.9975586, "punctuated_word": "The" }, { "word": "quick", "start": 0.16, "end": 0.4, "confidence": 0.9951172, "punctuated_word": "quick" }, { "word": "brown", "start": 0.4, "end": 0.64, "confidence": 0.9980469, "punctuated_word": "brown" } ] } ] } } bindings: [] extensions: - id: x-parser-unique-object-id value: DeepgramSttResultsEn bindings: [] extensions: *ref_0 - &ref_8 id: sttSlngDeepgramNova3EnSendError title: Stt slng deepgram nova3 en send error description: Receive error from Deepgram Nova 3 (English) type: send messages: - &ref_16 id: DeepgramSttError contentType: application/json payload: - name: Error description: Error from the Deepgram backend or gateway. type: object properties: - name: type type: string description: Error required: true - name: code type: string description: >- Gateway error code (e.g., backend_connection_failed, stt_metering_unavailable) required: false - name: message type: string description: Human-readable error description (gateway errors) required: false - name: variant type: string description: Deepgram error variant (e.g., SchemaError) required: false - name: description type: string description: Deepgram error description required: false headers: [] jsonPayloadSchema: type: object description: > Error message. May originate from the gateway (with code field) or from Deepgram directly (with variant and description fields). required: - type properties: type: type: string const: Error x-parser-schema-id: code: type: string description: >- Gateway error code (e.g., backend_connection_failed, stt_metering_unavailable) x-parser-schema-id: message: type: string description: Human-readable error description (gateway errors) x-parser-schema-id: variant: type: string description: Deepgram error variant (e.g., SchemaError) x-parser-schema-id: description: type: string description: Deepgram error description x-parser-schema-id: x-parser-schema-id: title: Error description: Error from the Deepgram backend or gateway. example: |- { "type": "Error", "code": "backend_connection_failed", "message": "Failed to connect to backend: 500 Internal Server Error" } bindings: [] extensions: - id: x-parser-unique-object-id value: DeepgramSttError bindings: [] extensions: *ref_0 sendOperations: - *ref_1 - *ref_2 - *ref_3 - *ref_4 - *ref_5 receiveOperations: - *ref_6 - *ref_7 - *ref_8 sendMessages: - *ref_9 - *ref_10 - *ref_11 - *ref_12 - *ref_13 receiveMessages: - *ref_14 - *ref_15 - *ref_16 extensions: - id: x-parser-unique-object-id value: /v1/stt/slng/deepgram/nova:3-en securitySchemes: - id: bearer name: bearer type: http description: > API key issued by SLNG. Pass as `Authorization: Bearer ` in the WebSocket upgrade request headers. scheme: bearer extensions: [] ````