The goal of this project is to implement an HD Radio receiver and transmitter in GNU Radio. HD Radio is standardized in NRSC-5. The latest version of the standard is NRSC-5-D, which can be found at https://www.nrscstandards.org/standards-and-guidelines/documents/standards/nrsc-5-d/nrsc-5-d.asp.
So far only a transmitter has been implemented. A stand-alone receiver for RTL-SDR is available here: https://github.com/theori-io/nrsc5/