EIA-608 and EIA-708 CC data can be decoded and over layed on the outputted video image. EIA-608 can often be passed through a device for decoding by an external device. EIA-708 data is not decoded and passed through as EIA-608 data capable of decoding and display by an external device. Unless the graphics card outputs composite video and the PCI DBVS card supports EIA-608 CC pass through, I do see the option of an external device decoding or manipulating the CC data.
I see that TV Guardian has a new HDMI product. This presents an interesting question for TV Guardian. To the best of my knowledge, HDMI does not carry CC information. Yet, their high definition product indicates support for HDMI closed captioning. What is the HDMI protocol or a list of HDMI devices that their unit is compatible with?
Let us know what you find out!