Resources

Limits

The limits of each Expression Measurement endpoint.

The tables below list the limits of each endpoint, grouped by media type. Limits that both endpoints of a media type share are listed once, before the tables for each endpoint. Each endpoint row links to the section of its guide that explains the limit and what happens when a request exceeds it.

Audio

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

LimitValue
Audio format16-bit PCM, 16 kHz, mono
Measurement interval3000 to 10000 ms of speech, default 3000
Measurement windowUp to the most recent 10 seconds of the utterance

Audio upload

LimitValue
ContainerA WAV file or headerless samples
Request size25 MB, a little over 13 minutes of audio

Audio realtime

LimitValue
Audio frameUp to 320 KB (10 seconds) of whole headerless samples
Message size1 MiB (1,048,576 bytes) for any WebSocket message; a larger one ends the session
Send rate1 second of audio per second

Video

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

LimitValue
Image formatJPEG
Pixels per image8,294,400 (3840x2160)
Faces measured per image2 by default, the largest. Contact support to raise it.
Faces listed per image32
Detection threshold0 to 1, default 0.9
Minimum face sizeAt least 1 pixel, default 60

Image upload

LimitValue
Image size2 MB
Request size25 MB for the whole multipart body

Video realtime

LimitValue
Message size2 MB for any WebSocket message; a larger one ends the session
Send rate3 frames per second
Consecutive measurement failures5, after which the session ends

Runs

LimitValue
Page size1 to 200 runs or events per page, default 50

Scores and sessions

  1. 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.
  2. Realtime sessions close after 30 seconds without a usable media frame. See Connection behavior.

Next steps

Errors

The codes returned when a request or frame exceeds a limit.

Billing

What each endpoint bills, and which rejected frames are not billed.