AV Timing Measurement and Correction for Digital Television

摘要

An invention for measuring, maintaining and correcting synchronization between signals which suffer varying relative delays during transmission and/or storage is shown. The present invention teaches measuring the relative delay between a plurality of signals which have suffered differing delays due to transmission, storage or other processing. The preferred embodiment of the invention includes the use of a marker which is generated in response to a second signal and combined with a first signal in a manner which ensures that the marker will not be lost in the expected processing of the first signal. Subsequently a first delayed marker is generated in response to the marker associated with or recovered from the first signal, and a second delayed marker is generated from the second signal. The first delayed marker and second delayed marker are compared to determine a measure of the relative timing or delay between said first signal and said second signal at said subsequent time.

主权项

1. An apparatus for generating a first set of markers in response to a relatively undelayed audio signal having one or a plurality of channels which is part of a digital television program having video comprised of frames and known number of audio samples corresponding to each frame according to one or more digital television standard which first set of markers are intended to be utilized with a second set of markers generated in response to a delayed version of the audio signal to determine delays of audio relative to video portions of the digital television program, the apparatus including:
a) an input circuit responsive to one channel or a combined plurality of channels of the digital audio portion of a digital television program to provide a first digital output portion capable of carrying the audio energy present in said channel or said combined plurality of channels over a first range of audio frequencies; b) an input filter circuit comprising a digital filter responsive to said first digital output portion to pass energy present therein which is within a second range of audio frequencies less than said first range of audio frequencies to provide a digital filter output, said input filter circuit operating to provide a first series of binary bits when said digital filter output is activated indicating the presence of energy at audio frequencies passed by said digital filter thus generating a set of binary bits per frame of video; c) a marker generator circuit responsive to said first series of binary bits to provide a series of master markers for each frame of video which is a smaller series of binary bits relative to said first series of binary bits, said marker generator further responsive to the digital video portion of said digital television program to relate the timing of said master markers to the timing of said digital video portion.