Apple has acquired Emotient, a startup with technology for recognizing emotions in people’s faces in video content, according to a report today. This is Apple’s latest in a series of recent acquisitions of companies well versed in artificial intelligence.

In reporting the deal, the Wall Street Journal did not say how much Apple paid for Emotient.

Emotient’s technology draws on deep learning, a type of artificial intelligence that involves training artificial neural networks on lots of data, such as video frames, and then directing it to make inferences about new data. This is a hot area where Flipboard, Snapchat, Microsoft, Facebook, Google, Pinterest, and others have done work.

The technology is notable for its ability to work even in less than ideal conditions. From the startup’s website:

Emotient’s technology not only captures these single frame expressions, but does so in the face of obstacles such as poor lighting, consumer-grade webcams, facial occlusions such as eyeglasses and facial hair. It also achieves this level of accuracy for multiple faces in a frame, potentially up to hundreds of faces in a 1080p video.

The technology can work in a browser or through an application programming interface (API), according to the website.

Other recent Apple AI acquisitions include Perceptio and VocalIQ.

San Diego-based Emotient announced a $6 million funding round in 2014. Investors include Handbag LLC and Intel Capital. Marian Bartlett, Ian Fasel, and Javier Movellan started the company in 2012. The startup has done work with Stoneware and the Golden State Warriors, according to a recent report from Bloomberg.

Apple sent VentureBeat its typical acquisition statement in response to an inquiry: “Apple buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans.”

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