A transmitter (14) of audio, video, or other real-time information reads the information from a persistent store (22) in which the real-time information has been stored in the Real-time-Transport Protocol (“RTP”) format (FIG. 4). A receiver (18) receives the information from the channel (16) through which the transmitter (14) has transmitted it, and the receiver may store the information in a persistent store (24) in RTP format instead of or in addition to playing it by applying it to an appropriate player (20). Parts of this communications circuit may be tested by a tester unit (26) that also employs RTP-format information from a persistent store (22).