Block HD Commercials?

Are there any options available for blocking commercials of live or DVR recorded video?
About the only options I know of are:
1. Media center pc -- way too expensive (I'm not paying $1000 for a $500 pc just because of HDCP.)
2. TIVO -- why would I waste money on that ripoff? (I'm not paying a monthly fee for something that could easily be implemented for free from a technical standpoint.)

I would prefer something that works on live HD feeds. For example, it would blank out the screen (maybe say the words "commercial" anytime it detects one.)

I have Comcast for cable service. As I understand, it I have to use Comcast's DVR for HD content (due to DHCP)... and it doesn't have the ability to block commercials. Is this correct? Do I have any other options for live feeds? How about for recording stuff from a DVR?

Now, the big problem I gather is HDCP, which prevents us from making cheap solutions. However, I don't suppose someone has made a commercial filter based on subtitles have they? This would get around DHPC.
For example, a device with a non-HDCP tutner receives a low quality picture. It checks the subtitles against a known list of commercials (like a spellchecker would). If one is found, it immediately sends a signal to a second device which cuts off the real, full-quality, HDCP HDMI cable going to the TV so the commercial is not shown.