1. A computer-implemented method for estimating voice quality in a voice over packet (VOP) network, comprising: at a computing device, collecting statistics from real-time transport protocol (RTP) and real-time transport control protocol (RTCP) streams in an actual VOP call, wherein the actual VOP call is a live call in a live traffic environment within the VOP network; measuring a delay, packet loss, and jitter from the collected statistics at the computing device; assigning constant values for a signal-to-noise ratio, an advantage factor, and simultaneous impairment factor based on an estimate derived from knowledge of the VOP network, wherein the signal-to-noise ratio, the advantage factor, and the simultaneous impairment factor are not calculated based on data collected during the live call; and using the delay, the packet loss, and the jitter from the collected statistics from the actual VOP call and the constant values to calculate a transmission rating factor using the ITU-T E-model.