15David Austerberry, The Technology of Video and Audio Streaming, 2nd ed. (Burlington, MA: Focal Press, 2005), 122. The MPEG-4 variety of AAC has been confusingly referred to as MP4, which reinforces the perception of AAC as the successor to MP3 while mixing apples with oranges: the “3” in “MP3” refers to Layer 3 in the MPEG family of standards, but there is no Layer 4 that would correspond to “MP4”; in this case, the “4” refers to the MPEG-4 group of standards, which provides for much more than AAC.