On a laptop, that's usually an output for showing HD video on your TV. Only on the highest end units would it possibly be bi-directional. That said, given the ultra-low bitrate you can achieve with your stream (150k-ish), using HDMI as a source would not gain you anything in quality over 1394, USB, or even S-video (and it might even cause you extra headaches given HDMI's native copy protection).