1. A multi-channel emulator system, comprising: a memory that stores a plurality of channel impairment profiles, wherein each channel impairment profile corresponds to a respective channel impairment type; a real-time clock that generates timing data; and a processor in communication with the memory and the real-time clock, wherein the processor is configured to: receive a selection of two or more of the plurality of channel impairment profiles, generate a composite impairment profile by combining the selected two or more channel profiles, the composite impairment profile specifying time-variant impairments, the composite impairment profile reflecting a combination of the respective impairment types of the selected channel profiles, and apply the time-variant impairments specified by the composite impairment profile to an input real-time data stream to generate an impaired real-time data stream, wherein a timing of the application of the time-variant impairments is based at least in part upon the timing data from the real-time clock.