can't open Blackmagic pocket cinema camera 4k .DNG video frame

Quite a long title, I beg your pardon guys.

Trying to open a dng generated by a Blackmagic pocket cinema camera 4k, I receive this message from Photoshop (and ACR doesn't open):

     "Could not complete your request because the file-format module cannot parse the file".

The dng is one of the many frame of the raw video produced by the camera.
It's a 3:1 or 4:1 compressed RAW, not the uncompressed one.

The same camera, shooting stills, creates a fully openable dng that doesn't create this issue.

Anybody know why and how to solve it?

Thanks,

best,

Stefano.