Samsung published a couple of technical blog posts today, providing some detail on the stacked sensor technology used in the new Galaxy S9 and S9 Plus smartphones, and specifically how this tech is used to power the devices' super-slow-motion mode.

This mode can record 960 frames per second at HD resolution for a duration of 0.2 seconds, which translates into 6 seconds playback time at 30 fps—32 times slower than standard video. The resulting videos can be reversed, exported as GIFs and edited in other ways.

To achieve the blistering fast frame rates, Samsung has adopted similar imaging technology to what we've previously seen on some Sony devices. The S9 sensor offers faster sensor readout-times, bandwidth and video processing of the application sensor than on previous Galaxy generations by using a three-layer stacked sensor design that consists of the CMOS image sensor itself, a 4x faster readout circuit, and a dedicated DRAM memory chip for buffering:

In addition to slow-motion, the stacked sensor helps reduce rolling shutter effects in video mode, and counter camera shake through frame-stacking methodologies.

“We were able to achieve a readout speed that is four times faster than conventional cameras thanks to a three-layer stacked image sensor that includes the CMOS image sensor itself, a fast readout circuit, and a dedicated dynamic random-access (DRAM) memory chip, which previously was not added to image sensors,” explained Dongsoo Kim. “Integrating DRAM allowed us to overcome obstacles such as speed limits between the sensor and application processor (AP) in a high-speed camera with 960fps features.”

You can see some of the Samsung super-slow-motion video results in the video below. Samsung's article on the technology is available on its blog, where you'll also find an interview with the team behind the new sensor.