MuEv

MuEv is an acronym for Mutual Event. MuEv is used in conjunction with the timing of sound and images, especially in television systems, to denote events which create temporally coincident sounds and images. These temporally coincident sound and image events may be utilized to measure the relative temporal offset of audio and video signals in television systems in order to measure or maintain proper audio to video synchronization. For example the movement and/or shape of lips and the corresponding sound which is created are MuEvs. MuEvs are utilized to determine the relative timing of audio and video signals to measure the degree of temporal match in lip sync measurement and correction systems. For example, the instant when lips begin to move in the video signal can be compared to the instant when there is a change of silence to sound in the audio signal are video and audio MuEvs respectively and can be compared to determine the relative timing of the two signals. As another example the forming of the round shape of the lips and the sound of "oo" are MuEvs which can also be compared to determine relative audio and video signal timing.
Proper audio to video synchronization is of considerable importance in television systems because any misalignment can seriously affect the effectiveness of the television program being conveyed by the system. See the report "Effects of Audio-Video Asynchrony on Viewer's Memory, Evaluation of Content and Detection Ability" by Reeves and Voelker for more information (a non-copyrighted PDF is available Reeves and Volker). Television industry standards organizations have become involved in setting standards for audio video sync errors. See for example ATSC Document IS-191 .
In a properly designed television system it is possible to acquire a television program (e.g. via television camera and microphone) with no temporal misalignment of the audio and visual components of that program. Several mechanisms exist for maintaining the proper timing of the audio and video signals carrying the program Managing Lip Sync, however with the extensive amount of audio and video signal processing that takes place in modern television system that proper timing relationship is frequently lost. In order to restore the proper timing, a human operator may critically view the television program and manually adjust audio or video signal delay until the timing appears correct, however this process is subjective and highly dependent on the operator's skill, training and experience as well as the operator's visual and hearing acuity. Often two operators will give different amounts of adjustment owing to the subjective nature of this process. By utilizing MuEvs it is possible to electronically measure and restore the audio and video signal timing thus eliminating the subjective errors of the operator.

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