Why hdmi input? Because my HD set top box provides hdmi output.
But again, HDMI output from your set top box is NOT meant to be recorded. It is meant to be displayed. Display devices have HDMI input connectors, and source devices have HDMI output connectors. These are not 2-way connectors, nor is the "in-the-clear de-compressed bitrate" intended to be recorded. It is meant to be displayed.
If you want to record the underlying MPEG-2 source transport streams for HD then you would use a firewire interface from your set top box (if it's a Motorola/FIOS family box, the older models of which have a pair of working firewire ports for exactly this reason)... connecting to a 5C-compliant DVHS VCR to archive anything HD (i.e. both copy-freely and copy-once content) to DVHS tape... via firewire.
Or, you can offload copy-freely content to PC, again via firewire.
But your set top box will not send transport stream data over firewire to a non-5C-compliant target device.
Nor will it send HDMI to anything but an HDCP-compliant display device (or AVR).
It's not just WMC that follows DRM/5C/HDCP rules and regulations. The industry defined what HDMI could and could not be used for, and what firewire interfaces from STB/DVR source devices could feed, specifically because they were hysterically concerned about digital piracy and making 100% perfect digital copies.
In fact, my JVC DT100U DVHS VCR will not send output over HDMI to a non-HDCP-compliant display device. You must use component video output (which is analog HD, not digital HD) if you don't have a qualified HDMI-capable display or HDTV.
I'm just saying... don't blame WMC for DRM. In fact, it was MS's agreement with Cablelabs to strictly enforce DRM that finally enabled the arrangement which permitted the Ceton cablecard-enabled 4-tuner device (which allows copy-once content to be recorded and displayed, albeit subject to some DRM rules and regulations) to be built, and sold... after many years of not being possible. Before this agreement only copy-freely clear-QAM content via cable coax was tunable.