[TheRandom1]

Would anyone know how to do this ?

[d3ibis]

u need to use mp4box (You will need to provide a drm_file for decryption)

command line:
MP4Box -decrypt drm_file file.mp4

The DRM file is an XML document containing mainly key information, KMS information, encryption instructions and eventually MPEG-4 IPMP(X) indications. The syntax is very basic and may be subject to changes in the future.

Just like any XML file, the file must begin with the usual xml header. The file encoding SHALL BE UTF-8. The file is then a collection of ISMACrypTrack elements placed at under an ISMACrypdocument root. Each element describes all ISMACryp information needed to encrypt a given track.

<ISMACryp>
<ISMACrypTrack trackID="..." key="..." salt="..." scheme_URI="..." kms_URI="..." selectiveType="..." ipmpType="..." ipmpDescriptorID="..." />
</ISMACryp>

Source: Here (https://gpac.wp.mines-telecom.fr/mp4box/encryption/ismacryp/)