  We show how to adapt a 0-f self-referencing technique to provide a single
shot absolute Carrier Envelope Phase (CEP) measurement by using the CEP
reference provided by difference frequency generation (DFG) between the
spectral wings of the fundamental pulse. Usually, the beat between the input
pulse and the DFG signal then provides feedback with which to stabilize the CEP
slip in a pulse train. However, with a simple extension we can get a single
shot absolute CEP measurement. Success relies on having well characterized
input pulses, and the use of accurate propagation models through the nonlinear
crystal -- these enable us to construct a mapping between the experimental
measurement and the CEP of the optical pulse.
