AU is an audio format standard in early web pages NEXT systems. It is also called u-law or Sparc-audio format. Typically, AU files can store audio data and annotation blocks. Initially, it was a headerless audio format, but newer versions have a header, thanks to the six unsigned 32.bit words.
MPEG-1 is a compression and encoding system defined by MPEG (Moving Pictures Experts Group). It creates multiple frame sequences of I, B, and P, with the I frame containing all picture data. The B and P frames only store information about the changes on the last I frame. Typically, MPEG-1 uses 1.2 Mbps data rate, which is the speed rate of CD-ROM.