To provide a data transmitter capable of canceling deviation in a time base at the side of a reproducing unit by simple processing without making a network complicated.

A transmission-side terminal device transmits control data (RTCP) to reception-side terminal devices (S101, S201), and calculates the transmission time of RTP from time required until receiving the response, and the analysis result of response data (S104, S204). Then, information on the calculated transmission time is mutually transferred to other transmission-side terminal devices (S105, S205), and own transmission time is compared with transmission time from other transmission-side terminal devices. As a result, when the own transmission time is short, a time stamp value is corrected so that the differential value of the transmission time is added (S107, S207), and the corrected time stamp value is added to RTP (S108, S208) in later RTP transmission.

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