If you already have the decryption key, this is the most straightforward method.
Even if technically possible, decrypting protected streams undermines content licensing. Streaming services pay billions for rights; unauthorized decryption allows redistribution or offline archiving without compensation. For personal use, most services already offer offline downloads within their apps (using DRM). Attempting to extract a clean file breaches terms of service and erodes trust in digital distribution. decrypt mpd file verified