The video comes from YouTube user Nabil Fathi, and it comes with the following description:

This is just a teaser of upcoming hack similar to magic lantern that will be available for the Sony a7a, possible on the a7s II but not sure yet.
Higher bitrate, better subsampling (HDMI 10-bit 4:2:2), 4K recording, etc... (Do not misunderstand this part, what you see on the video, it is a simple port for fun, have a custom app that offer clearly more than that to come. This video doesn't show anything related to 4K, simply related to a7s access).

This hack — if it is, in fact, legitimate — is reportedly made possible by a reverse engineering of the Sony PlayMemories app store, which allows certain apps to be installed on newer Sony cameras.

The latest Sony cameras include an Android subsystem which allows to install apps from the proprietary Sony PlayMemories Camera app store. This application replicates the functionality of the Sony store and allows you to install custom Android apps on your camera.

With all of that said, there are definitely reasons to be skeptical of this whole thing. First and foremost, most of the information on the camera's screen in that video is gibberish. H.263 hasn't been used as a compression format for upwards 10 years. The resolution is completely arbitrary. 20fps might have been fast enough for a Buster Keaton flick 80 years ago. Plus the whole interface is essentially the same as the IgCamera Android appMore importantly, Sony's Senior Manager of Technology has come out and said that the BIONZ-X processors used in Alpha-series cameras are only capable of processing 8-bit 4:2:2 video. In other words, the claim that this hack will enable 10-bit output from the a7s is probably not true.

On the flip side of this, it wouldn't be the first time that someone managed to coax higher internal resolutions out of a Sony camera. Around this time last year, the F5 was hacked to shoot 4K internally. All in all, I'm not convinced of the authenticity of this hack. But if it turns out to be true, Sony a7s owners everywhere will surely rejoice.

Source: Nabil Fathi - YouTube