Sounds like this is locked into windows via the Media Foundation APIs
There may be lock in, but it's not exclusive to Microsoft:
Media Source Extensions (MSE) This specification extends HTMLMediaElement to allow JavaScript to generate media streams for playback. Allowing JavaScript to generate streams facilitates a variety of use cases like adaptive streaming and time shifting live streams.
Encrypted Media Extensions (EME) This proposal extends HTMLMediaElement providing APIs to control playback of protected content.
Web Cryptography API (WebCrypto) This specification describes a JavaScript API for performing basic cryptographic operations in web applications, such as hashing, signature generation and verification, and encryption and decryption.
They're all W3C standards track specifications. The first two have editors from the same three corporations; Google, Microsoft and Netflix. Google, in particular, can't tolerate not being capable of playing Netflix (10% of the population of the US subscribes to this) on its platforms (Android and Chrome OS.) It already works on both and you can take it for granted that Google expects to achieve parity with these specifications.
The last specification is not specific to streaming; it's a general purpose Javascript API to perform common cryptographic operations.