VQmon is a modular performance analysis software agent that supports VoIP, IP video conferencing, IPTV, and video streaming services. It is a compact, portable software library that can be integrated into a wide range of host environments including probes, routers, ONUs, handheld test devices, IPTV set-top boxes, and video conferencing equipment providing real-time quality analysis of IP voice and/or video streams with low impact on host resources including CPU and memory. VQmon is available as a compiled binary for Windows, Linux, Solaris, BSD, and standard processor environments. The VQmon library includes both interface-based and stream-based APIs, enabling host applications to non-intrusively monitor single or multiple concurrent voice or video streams and to obtain real-time QoE scores and a rich set of diagnostic metrics on a per-interface, per-stream, or per-call/per-video session basis. Key API functions enable host applications to initialize streams, indicate received packets, retrieve quality metrics, and terminate streams.