Stream TV shows from HDTV to Mac
"I saw your video about connecting a Mac Mini to an HDTV. I've got a Mac Mini and an HDTV and I want to stream tv shows from the HDTV to the Mac (so that I can do HD screen captures). Is this possible?"
It is possible to record and capture HDTV with your Mac, although what you can actually capture varies depending on what your HD video source is (Cable, Satellite, over-the-air) and how powerful your Mac is. I'll outline a few potential solutions that should deliver some or all of what you'd like to do in streaming HDTV to your Mac.
Mac Mini, MacBook, and MacBook Pro hardware are all somewhat limited in HD video capture options because they don't have space for an internal add-on card and USB capture options tend to be hobbled in what types of video can be captured. If you have a Mac workstation, with PCI slots for additional cards, you have more options. That doesn't mean you have no HDTV capture options, just that you might need to get creative.
USB HDTV Capture Options
The most popular USB HDTV capture option for Macs is also one of the only USB HD capture options. Elgato Systems EyeTV Hybrid will capture over-the-air ATSC HDTV programming, as long as you connect an antenna directly to the EyeTV Hybrid unit. The EyeTV also supports capture over component inputs, but not at HD resolutions, so running component outputs from your cable box to your Mac won't get you HD resolution.
If you have an HD camcorder, you might be able to capture HD television with your camcorder. A few HD camcorders accept HD input via component-in. You'll need to check the manual on your camcorder to see if this is supported. If it is, you can capture HDTV with your camcorder and import the recordings to your Mac. In a smaller number of cases, the camcorder can pass the signal through to your Mac directly, so you could capture HDTV on your Mac by way of the camcorder. Again, it's necessary to consult the manual on this.
External Capture Hardware
A third (more expensive) option would be to capture HDTV using an external HD DVR and then transfer the clips to your Mac. If you plan to go this route it might be cheap to upgrade to a more expensive Mac capable of recording HDTV directly.