Here are some straightforward designs for a closed captioning + XDS data decoder – and the circuit is simple enough to assemble on a small piece of perfboard. Kevin explains more -

This is a closed caption decoder that sends the captoin text to a computer via USB. Using a comptuer to display the captions keeps the entire picture visible, so nothing is obscured by the captions. It also allows quick review of recent captions and allows saving them. The USB interface uses the popular FTDI USB to serial chip, so it appears a a COM port. Ordinary terminal software is all that is required to use this.

In case you’re not familiar with XDS – Extended data services is optional data which can be sent along with a broadcast video signal. It’s often used for setting VCR clocks automatically, V-Chip ratings, or timecode references.

DIY Closed Caption and XDS decoder with USB interface – Link