This is a rather broad assumption. I have seen 40ms, 60ms and even 80ms in the wild. It all depends on what you want to do. It lowers overhead and increases efficiency on the wire.
/b
On Feb 12, 2010, at 5:24 AM, Nikolay Kondratyev wrote:
By the way, I know that one can use different packetization times for the same codec, but I’ve never heard, that somebody really uses 30 ms for G711Alaw. Always 20ms.