Limits | Hume API

Audio upload takes up to 25 MB of 16-bit, 16 kHz mono audio, a little over 13 minutes, and image upload takes JPEG images of up to 2 MB each, up to 25 MB in all. Realtime sessions take up to 1 second of audio per second or 3 video frames per second, and each organization can make up to 600 requests per minute. Limits that both endpoints of a media type share are listed once, before each endpoint’s table. Each table names the error a request, frame or message outside that limit returns. See Errors for what each code means.

Audio

Both audio endpoints share these limits. Audio upload and Audio realtime explain them.

Limit	Value	Outside the limit
Audio format	16-bit PCM, 16 kHz, mono	`audio_decode_failed` on upload, `config_invalid` in `session.update`
Measurement interval	3000 to 10000 ms of speech, default 3000	`config_invalid`
Measurement window	Up to the most recent 10 seconds of the utterance	No error. Earlier speech is in earlier measurements.

Audio upload

Limit	Value	Outside the limit
Container	A WAV file or headerless samples	`unsupported_media_type`
Request size	25 MB, a little over 13 minutes of audio	`audio_too_long`

Audio realtime

Limit	Value	Outside the limit
Audio frame	Up to 320 KB (10 seconds) of whole headerless samples	`invalid_audio_frame`
Message size	1 MiB (1,048,576 bytes) for any WebSocket message	`message_too_large`, which ends the session
Send rate	1 second of audio per second	`rate_limited`

Video

Both video endpoints share these limits. Image upload and Video realtime explain them.

Limit	Value	Outside the limit
Image format	JPEG	`unsupported_media_type` on upload, `invalid_image_frame` in realtime
Pixels per image	8,294,400 (3840x2160)	`image_too_large` on upload, `invalid_image_frame` in realtime
Faces measured per image	2 by default, the largest. Contact support to raise it.	No error. Other faces are listed without scores.
Faces listed per image	32	No error. The least confident faces past 32 are left out.
Detection threshold	0 to 1, default 0.9	`config_invalid`
Minimum face size	At least 1 pixel, default 60	`config_invalid`

Image upload

Limit	Value	Outside the limit
Image size	2 MB	`image_too_large`
Request size	25 MB for the whole multipart body	`image_too_large`

Video realtime

Limit	Value	Outside the limit
Message size	2 MB for any WebSocket message	`message_too_large`, which ends the session
Send rate	3 frames per second	`rate_limited`
Consecutive measurement failures	5	`internal_error` on the fifth, which ends the session

Runs

Limit	Value	Outside the limit
Page size	1 to 200 runs or events per page, default 50	`invalid_request`

Rate limits

Limit	Value	Outside the limit
Requests	600 per minute per organization	`429 Too Many Requests`

The limit counts requests to every Expression Measurement endpoint over a sliding 60-second window: audio and image uploads, realtime handshakes and run requests alike. Every API key in an organization shares it. Frames sent within a realtime session do not count toward it; the session’s send rate limits them instead: 1 second of audio per second for audio and 3 frames per second for video. A 429 carries a Retry-After header with the number of seconds to wait before retrying. See Handling errors.

There is no separate limit on how many uploads or realtime sessions an organization runs at once. When the service is at capacity, an upload is refused with 503 server_busy and a Retry-After header.

Scores and sessions

Each score array has its own cutoff. Vocal expressions are included when judged present, voice attributes at 0.725 or above, and face scores above 0.1. See Reading probabilities.
Realtime sessions close after 30 seconds without a usable media frame. See Connection behavior.

Next steps

Errors

Learn what each error code means and which requests to retry.