This attribute indicates the encoding currently being performed.
g711 indicates that pulse code modulation (PCM) defined by ITU-T
G.711 is being performed. g726 indicates that adaptive differential
pulse code modulation (ADPCM) defined by ITU-T G.726 is being
performed. g728 indicates that the Low Delay Coded Excited
Linear Predictive Coder (LD-CELP) algorithm defined by ITU-T
G.728 is being performed. g729 indicates that the Conjunctive
Structure Algebraic Code Excited Linear Predictive Coder
(CS-ACELP) algorithm defined by ITU-T G.729 is being
performed. v27 indicates that the algorithm defined by ITU-T V.27
is being performed. v29 indicates that the algorithm defined by
ITU-T V.29 is being performed.