Abstract: Information relating to a playback of divided static media data included in static media transmission data is stored in static media transmission data previous than the static media transmission data, and transmitted, thereby making it possible to determine whether there is no divided static media data originally or lost when the divided static media data is not received. Accordingly, in the case where static media such as timed text and the like is used in distribution of streaming type, when receiving no static media data, a data receiving apparatus determines whether there is no media data to be next displayed or media data is lost in the course of transmission to notify a user of loss of media data correctly. Moreover, Moreover, it is possible to reduce time required for packet loss detection to execute a retransmission request without increasing pre-buffering.

Abstract: Phase-change-type optical recording medium comprises a first dielectric layer, a recording layer made of a phase change material, a second dielectric layer and a reflecting layer wherein the thicknesses of the first and second dielectric layers are determined for a given thickness of the recording layer so that the following conditions are satisfied;.DELTA.A+.DELTA.R.gtoreq.20% and .DELTA.A.gtoreq.5%wherein.DELTA.A=A(cry)-A(amo),A(cry), A(amo): light absorption rates of the recording layer in the crystal state and amorphous state, respectively,.DELTA.R=R(cry)-R(amo),R(cry) and R(amo): light reflection rates of the recording lates in the crystal state and amorphous state, respectively.