 ), to become Layer III.ASPEC was itself based on "Multiple adaptive Spectral audio Coding" (MSC) by E. F. Schroeder, "Optimum Coding in the Frequency domain" (OCF) the doctoral thesis by Karlheinz Brandenburg at the University of Erlangen-Nuremberg, "Perceptual Transform Coding" (PXFM) by J. D. Johnston at AT&T Bell Labs, and "Transform coding of audio signals" by Y. Mahieux and J. Petit at Institut für Rundfunktechnik (IRT/CNET).MP3 is a frequency-domain audio transform encoder.