Selective encryption to enable trick play

摘要

Certain embodiments consistent with the present invention involve a method of selectively encrypting and decoding digital video content. Certain of the packets are selected for encryption according to a selection criterion, wherein the selected packets exclude packets containing start of file (SOF) headers. The selected packets are encrypted while retaining the packets containing the SOF headers unencrypted to form selectively encrypted digital video content. In decoding selectively encrypted digital video content, offsets are calculated for at least one of I frames and P frames from the SOF headers and the calculated offsets are stored as an offset table. The offset table can then be accessed to enable trick play of the selectively encrypted digital video content.