Abstract: A playback system in a digital cinema network synchronizes the presentation of visual and aural content by deriving timing information for packets of information that are conveyed in video and audio data streams, examining the timing information to determine if any misalignment between the two data streams is likely to be perceptible and, if the misalignment is deemed to be perceptible, introducing delays into one or both data streams to correct the misalignment. If the audio data stream precedes the video data stream, the audio data stream is delayed by an integer number of audio sample periods. If the video data stream precedes the audio data stream, the video data stream is delayed by an integer number of video frames and the audio data stream is delayed by an integer number of audio sample periods.

Abstract: A free-running secure clock in a computing device that is adjustable by a user of the device so long as cumulative adjustments do not exceed a predicted clock drift. The clock may be initially set by the user or by a trusted time authority or the like. Such a clock may be required in a trust-based system that measures a temporal requirement against the clock.