High Resolution Audio is defined as "lossless audio that is capable of reproducing the full range of sound from recordings that have been mastered from better than CD quality music sources."
In addition to this definition, four different Master Quality Recording categories have been designated, each of which describes a recording that has been made from the best quality music source currently available.
The descriptors for the Master Quality Recording categories are as follows:
From a PCM master source 48 kHz/20 bit or higher; (typically 96/24 or 192/24 content)
From an analog master source
From a CD master source (44.1 kHz/16 bit content)
From a DSD/DSF master source (typically 2.8 or 5.6 MHz content)