One of the largest controversies involving the U.S. digital radio standard, HD Radio, has been its proprietary nature. The technology’s owner,
iBiquity DTS Tessera Xperi Corporation, has refused to make public all the necessary technical information within the standard, dubbed by the National Radio Systems Committee as NRSC-5; this ostensibly prevents anyone from developing or manufacturing any HD-related transmission or reception technologies without express licensure from Xperi.
The specific “black box” that has kept the technology proprietary has been the algorithm Xperi uses to encode and decode HD audio signals. If you look at the publicly-available NRSC-5 documentation, you find no meaningful detail about this aspect of HD technology beyond a description of how it works.
This was a site of controversy during HD’s tortured development: initially, the standard was to utilize an algorithm derived from publicly-accessible code – but once the FCC gave the standard its blessing, then-developer iBiquity swapped out the codec under which the technology had been tested with a new one that it had ginned up wholly in-house. But it performed so poorly that HD’s proprietors replaced it again with the variant onboard transmitters and receivers today.