Update March 10th, 2018:
It seems this update only fixes Netflix HD playback and that other streaming services still only offer SD quality. It's unclear if other services, like Amazon Prime and Google Play Movies, are going to enable HD support for OnePlus devices.
On OnePlus devices, it has not been possible to watch Netflix, Amazon Prime Video and other video streaming services in HD quality. This is caused by the lack of support for Widevine L1 encryption, a DRM (Digital Rights Management) feature required by the content creators of these services. Content creators require the use of DRM to prevent their works from being distributed without their permission (such as downloading and streaming from other websites).
Recently, OnePlus announced that a DRM firmware update is available to allow streaming DRM-protected video in HD quality. It brings the aforementioned Widevine L1 DRM to the latest OnePlus devices: the OnePlus 5 and 5T.
That's great, but how do I get this update? I don't see it in Oxygen Updater!
If you are not using a OnePlus 5 or 5T: you can't get this update. It is only available for the latest OnePlus devices. Until OnePlus decides to change their mind, you're only able to view the SD quaity streams of DRM-protected videos.
For users with the latest devices, it comes with a big catch: you can't download this update - at least not right now.
To get the update, you'll have to send your device to OnePlus. OnePlus covers shipping costs for customers in Europe, North America, India and China. Details about this upgrade program are available here: Info about DRM Firmware upgrade from OnePlus
It basically involves creating a support request, backing everything up, sending in your phone and receiving it back with this upgrade installed. From then on, you'll have permanent access to the HD-quality streams of all popular movie / tv-show streaming platforms.
You will likely LOSE all personal information when you send in your phone to OnePlus. Keep this in mind before applying for this update!
I dont's want to send in my phone. Will a download become available?
It's not yet known if this update becomes available to download, but once it is, you'll get a push notification from Oxygen Updater. Stay tuned!
I already sent my phone in for this update and would like to help checking if it can be made available to download. Is this possible?
You may be able to help other users if you've already got this update on your phone! Please contact me (@arjan1995) or my friend Titokhan (@titokhan) on the Discord channel of this app. Not a member yet? See one of the earlier news stories to learn more about the Discord channel.
However: the DRM update will only be distributed if this is legally possible. Chances are pretty high, that this is not the case. If the legality cannot be confirmed, public distribution of the update will not be possible.
Source: XDA-Developers [link]
Icon credit: Neurogadget.net