Turns, barge-in and DTMF

Turns

The transport is turn-based. An energy-based voice activity detector cuts the caller’s audio into utterances: speech ends a turn after silence-ms of silence, or after max-turn-ms. Each turn is delivered to the flow as one call-turn message with the audio and deterministic acoustic features (duration, voiced ratio, pitch and energy contours, overtalk).

Turn detection needs a continuous media stream. A gateway that sends nothing during silence ends a turn only when audio resumes or at max-turn-ms.

Barge-in

Playback is paced in real time at 20 ms per frame. When the caller starts speaking while an answer plays, the transport stops sending, so an interrupted answer reports interrupted: true and the flow can react. A play can be made uninterruptible with x-barge-in: false.

DTMF

Keys arrive as call-dtmf messages, and the flow can send keys with voip://dtmf (to enter a conference PIN, for example). A flow collects digits with a loop: one wait per key until a terminator such as # or a timer, with a counter for retries. Keys pressed while a prompt plays are kept and handled in order when it ends, so a caller who knows the menu can type ahead. The dtmf operation never echoes the digits back, because a PIN is a secret.

The ivr-dtmf example is a complete menu and PIN flow built this way.