Single Media Streams WebSocket session. All frames are JSON-encoded text
frames carrying an `event` discriminator. The session begins with
`connected`, then `start`, followed by a continuous stream of `media`
frames and optional `dtmf` / `mark` frames, terminated by `stop`.
In bidirectional mode (``), the customer server may
additionally send `media`, `mark`, and `clear` frames b
Frames sent FROM the customer server TO Twilio. Only valid in
bidirectional Media Streams (``).
subscribe
receiveFromTwilio
Frames sent FROM Twilio TO the customer server.
Messages
outboundMedia
Base64-encoded mulaw/8000 audio sent from the customer server to Twilio
for playback on the call. Bidirectional Media Streams only.
Content-Type: application/json
outboundMark
Sent after one or more outbound `media` frames. Twilio will echo the
mark back to the customer with the same `mark.name` once the preceding
audio has finished playing. Bidirectional Media Streams only
Content-Type: application/json
clear
Interrupts and discards any audio that Twilio has buffered for
playback. Bidirectional Media Streams only.
Content-Type: application/json
connected
First frame sent by Twilio when the WebSocket opens.
Content-Type: application/json
start
Sent once at stream initiation with stream metadata.
Sent when a DTMF digit is detected on the inbound track. Bidirectional
Media Streams only.
Content-Type: application/json
mark
Echoed back to the customer server when a previously sent outbound
audio buffer with a matching `mark.name` has finished playing.
Bidirectional Media Streams only.
Content-Type: application/json
stop
Sent once when the stream terminates.
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.