A passive method for monitoring voice-over-IP call quality with ITU-T objective speech quality measurement methods

Voice signal processing algorithms such as P.861 PSQM (perceptual speech quality measure) and P.862 PESQ (perceptual evaluation of speech quality) have been recommended by the ITU-T for the objective measurement of subjective speech quality. The algorithms have been implemented in commercially available products to measure the end-to-end speech quality of voice-over-IP (VoIP) calls. Such measurements are carried out by transmitting a packetized reference speech signal and then applying PSQM or PESQ to the received signal and the original reference to obtain an objective quality score. The measurements are intrusive since test calls are injected into the network. We develop a novel passive method for measuring and monitoring speech quality in live (i.e. in progress) VoIP calls. In contrast to the intrusive methods, the passive method does not require the transmission of any reference speech signal. Instead, the method operates directly on VoIP packet streams copied from the network and applies the ITU-T objective speech quality processing algorithms to the copied voice signals and specially constructed 'pseudo-packet' stream signals. Thus there is no need for any sending devices. The proposed passive method inherits the accuracy that is already provided by the ITU-T objective methods.