| 摘要 |
Logical content is defined by start/end times into a VoD media offering. The calculation of byte-range markers corresponding to the start/end times is distributed among the STBs to first request the particular logical content. Upon receiving an initial request for a logical content offering, an IPTV AS returns a VoD media file URL, start/end times, and null values of byte-range markers corresponding to the start/end times. In response to the null values, the initially-requesting STB downloads the entire VoD media file from a Download Media Server, and calculates the byte-range markers by comparing the start/end times to timestamps in non-encrypted headers in the VoD media file. The non-null byte-range markers are transmitted back to the IPTV AS, which provides them to STBs subsequently requesting the same logical content. The subsequently-requesting STBs may download only the logical content by providing the non-null byte-range markers to the Download Media Server.
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