Built by Coding Technologies, the brains behind the HDC codec already in use by HD Radio, HDC Surround adds 5.1 channel capability to HDC. By building on HDC, HDC Surround provides a unique solution for backwards compatible 5.1 surround sound over HD Radio. This feature allows stations to upgrade their broadcasts to HDC Surround without negatively impacting their core stereo signal.

With the HDC Surround system, stations and receivers only need one codec to accomplish both stereo and 5.1 channel broadcasts over HD Radio. Existing receivers will receive the broadcast as stereo and HDC Surround enabled receivers will receive the same broadcast as 5.1 channel surround.