AMD Strengthens Security Solutions through Technology Partnership with ARM There is a ARM trustzone processor in every AMD APU that has a UVD which uses Xtensa processors as software accelerators for codecs. ALL critical DRM code must run in a Trustzone TEE and that includes the codec, encryption and decryption, Player, DTCP-IP for DLNA and Vidipath, HDCP2, Miracast, AACS 2 and BD+ for UHD Blu-ray and the embedded Playready for IPTV services like Neflix.
Since the UVD uses Xtensa processors and they are also vision processors; AMD APUs have ARM code middleware for gesture recognition using those Xtensa processors.
The XB1 has a huge block of ARM and Cadence (Xtensa and more) IP, all the accelerators and move controllers are Cadence IP on a ARM AXI bus.
A week after Microsoft announced their HEVC encode and Decode in the XB1, AMD announced they use the same hardware in UVD to do the same in Kaveri and Carrizo. Look up AMD UVD
I have a thread on it here but I first started discussing ARM in the PS4 and XB1 in 2012 at Semiaccurate.