Convert aac to nist

What is the difference between .aac and .nist?

Developer: Bell Labs, Fraunhofer Institute, Dolby Labs, Sony and Nokia; National Institute of Standards and Technology

Description: Compressed audio file similar to an .MP3 file, but offers several performance improvements; examples include a higher coding efficiency for both stationary and transient signals, a simpler filterbank, and better handling of frequencies above 16 kHz; maintains quality nearly indistinguishable from the original audio source.; SPHERE (SPeech HEader Resources) is a file format defined by NIST (National Institute of Standards and Technology) and is used with speech audio. SoX can read these files when they contain μ-law and PCM data. It will ignore any header information that says the data is compressed using shorten compression and will treat the data as either μ-law or PCM. This will allow SoX and the command line shorten program to be run together using pipes to encompasses the data and then pass the result to SoX for processing.