transcription_session.update

After a successful Realtime API connection, you must send this event before sending audio. It configures session metadata (audio format, language, etc.) for this session.

Features not yet available

• You cannot change metadata mid-session. To change it, create a new connection.
• Only same-language transcription is supported (language = target_language).
• turn_detection=true is not yet supported.

typestringrequired

Fixed value

Possible values: [transcription_session.update]

session objectrequired

Realtime API session metadata (audio format, language, etc.).

input_audio_formatstring

Audio format. For all formats, audio must be 1 channel (mono).

For example, pcm16 is 16-bit PCM audio.

For twilio, you can send audio using the Twilio Media Streams API audio format as-is.

Possible values: [pcm16, float32, twilio]

Default value: pcm16

input_audio_sample_rateinteger

Input audio sample rate

Default value: 24000

input_audio_number_of_channelsinteger

Input audio number of channels

Default value: 1

input_audio_transcription objectrequired

Settings for transcribing input audio.

languagestringnullable

Specify the input audio language using an ISO-639-1 code.

Optional, but specifying it may improve transcription accuracy and/or latency.

Possible values: [en, ja]

target_languagestringrequired

Specify the transcript language using an ISO-639-1 code.

Possible values: [en, ja]

turn_detectionboolean

Whether to enable turn detection. If false, the conversation.item.input_audio_transcription.completed event is not sent.

Default value: false

transcription_session.update

{
  "type": "transcription_session.update",
  "session": {
    "input_audio_format": "pcm16",
    "input_audio_sample_rate": 24000,
    "input_audio_number_of_channels": 1,
    "input_audio_transcription": {
      "language": "en",
      "target_language": "en"
    },
    "turn_detection": false
  }
}