I have a 2013 iMac and would like to be able to hook it up to a DVR cable receiver (Time Warner Cable -- NYC). I'm not looking to record television programs on my iMac since I already have a DVR cable receiver -- I just want the iMac to be able to show live programs on it as if it were a regular TV hooked up to a cable receiver . There are two issues that I see -- 1. Being able to hook it up as the DVR cable box uses HDMI, and my iMac only has USB and Thunderbolt inputs. 2. What program I would have to have to have to allow the output of the cable receiver to show on the iMac. Thanks.