AsyncAPI channel · Retell AI · Retell AI WebSocket APIs

audio/{call_id}

Audio WebSocket channel (deprecated). Carries raw audio bytes from the frontend microphone to Retell, and a mix of raw audio bytes plus JSON / string control events from Retell back to the frontend.

Open source AsyncAPI → All Retell AI channels Retell AI provider profile
Provider: Retell AI AsyncAPI: v2.6.0 Spec: Retell AI WebSocket APIs Operations: 2 Messages: 6

Channel address

audio/{call_id}

Parameters

Operations

publish
clientToRetell
Messages sent from the frontend client to Retell.
retellToClient
Messages sent from Retell to the frontend client.

Messages

ClientAudioFrame
Raw microphone audio bytes streamed in 20-250ms chunks.
Content-Type: application/octet-stream
AgentAudioFrame
Raw binary agent audio response bytes, emitted when `enable_audio_alignment=false`.
Content-Type: application/octet-stream
AudioClear
String literal "clear" sent when the user interrupts the agent so the client can flush any buffered agent audio.
Content-Type: text/plain
AudioUpdate
Live call update containing transcript and optional turn-taking info.
Content-Type: application/json
AudioAlignment
Emitted when `enable_audio_alignment=true`. JSON envelope containing base64-encoded agent audio aligned with the corresponding text.
Content-Type: application/json
AudioMetadata
Custom metadata forwarded from the LLM server to the frontend.
Content-Type: application/json

About AsyncAPI

The AsyncAPI specification describes event-driven APIs the way OpenAPI describes request/response APIs. A channel is the named pipe — a webhook URL, a Kafka topic, a WebSocket route, an MQTT subject — that producers and consumers publish or subscribe to. Each channel carries one or more messages with structured payloads, and an operation declares whether a given party sends or receives on that channel.

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