Apple has published its latest machine learning journal entry with a new article detailing the challenges of implementing facial detection features while maintaining a high level of privacy.

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Apple started using deep learning for face detection in iOS 10. With the release of the Vision framework, developers can now use this technology and many other computer vision algorithms in their apps. We faced significant challenges in developing the framework so that we could preserve user privacy and run efficiently on-device.

The new journal entry explains how the facial detection algorithm works locally on your iPhone without relying on information leaving your device:

Apple’s iCloud Photo Library is a cloud-based solution for photo and video storage. However, due to Apple’s strong commitment to user privacy, we couldn’t use iCloud servers for computer vision computations. Every photo and video sent to iCloud Photo Library is encrypted on the device before it is sent to cloud storage, and can only be decrypted by devices that are registered with the iCloud account. Therefore, to bring deep learning based computer vision solutions to our customers, we had to address directly the challenges of getting deep learning algorithms running on iPhone.

That requires the right hardware resources to pull off while maintaining efficiency:

We faced several challenges. The deep-learning models need to be shipped as part of the operating system, taking up valuable NAND storage space. They also need to be loaded into RAM and require significant computational time on the GPU and/or CPU. Unlike cloud-based services, whose resources can be dedicated solely to a vision problem, on-device computation must take place while sharing these system resources with other running applications. Finally, the computation must be efficient enough to process a large Photos library in a reasonably short amount of time, but without significant power usage or thermal increase.

Apple launched its machine learning journal over the summer and has published multiple entries including one on how “Hey Siri” works on iPhone and Apple Watch. You can read the complete latest entry here.


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