Specifies the Preferred Audio Encoding Packet Size in milliseconds.
For G.711 encoding mode, valid values range from 10 ms to
40 ms, in increments of 5 ms. The default value for G.711 is 10 ms.
For G.729 encoding mode, valid values from 10 ms to 40 ms, in increments of 10 ms. The default value for G.729 is 20 ms.