When Blu-ray came out, it came with all sorts of DRM madness (AACS, BD+, etc.) which persists to this day. However playback on PCs still ultimately involved som

When Blu-ray came out, it came with all sorts of DRM madness (AACS, BD+, etc.) which persists to this day. However playback on PCs still ultimately involved some kind of proprietary player software which contains keys to decrypt the content. Obviously, these keys could be extracted from the player software to decrypt DVDs. In other words, it's the flaw with all DRM schemes. For UHD/4K Blu-rays, the DRM scheme was renewed (AACSv2). As far as I can tell, studios seemed to decide that the above model was too insecure and to require something more for PC playback of UHD Blu-rays. The requirement seems to basically be that some kind of platform-integrated hardware DRM is involved so that the CPU never sees the decrypted video (or equivalent; presumably SGX is used to lock the decrypted content inside an enclave which is remotely attested and then securely transported to the GPU somehow. GPUs also have had this kind of hardware DRM functionality added to support this use case but I don't have the details to hand as they're not to my knowledge public.)