Widevine L1 requires a trusted execution environment for decrypting video and only showing it on HDCP monitors. It's built on top of Intel PAVP, AMD secure display, or ARM TrustZone in the case of ARM chromebooks and Android devices. TPM is not involved, except in the ARM case where I believe it is used for antirollback counters (on x86, the security coprocessor would probably have that responsibility).
