Comparative Study of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) Preference for Bt and Non-Bt Soybean Cultivars. Vilmar Bueno Dos Santos. ITU-R BT. () Relative Timing of Sound and Vision for Broadcasting. International Telecommunication Union, Geneva. Find the most up-to-date version of ITU-R BT at Engineering
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ITU-R BT. Relative Timing of Sound and Vision for Broadcasting, – Open Access Library
Audio-to-video synchronization also known as lip syncor by the lack of it: AV synchronization can be an issue in televisionvideoconferencingor film. In industry terminology the lip sync error is expressed as an amount of time the audio departs from perfect synchronization with the video where a positive time number indicates the audio leads the video and a negative number indicates the audio lags the video. Digital or analog audio video streams or video files usually contain some sort of synchronization mechanism, either in the form of interleaved video and audio data or by explicit relative timestamping of data.
The processing of data must respect the relative data timing by e. If the processing does not respect the AV-sync error, it will increase whenever data gets lost because of transmission errors or because of missing or mis-timed processing.
Examples of transmission broadcastingreception and playback that can get the AV-sync incorrectly synchronized:. When a digital or analog audio video stream does not have some sort of explicit AV-sync timing these effects will cause the stream to become out of sync:.
The result typically leaves a filmed or televised character moving his or her mouth when there is no spoken dialog to accompany it, hence the term “lip flap” or “lip-sync error”. The resulting audio-video sync error can be annoying to the viewer and may even cause the viewer to not enjoy the program, decrease the effectiveness of the program or lead to a negative perception of the speaker on the part of the viewer.
Television industry standards organizations, such as the Advanced Television Systems Committeehave become involved in setting standards for audio-video sync errors.
Because of these annoyances, AV-sync error is a concern to the television programming industry, including television stations, networks, advertisers and program production companies. Unfortunately, the advent of high-definition flat-panel display technologies LCD, DLP and plasmawhich can delay video more than bf.1359-1, has moved the problem into the viewer’s home and beyond control of the television programming industry alone.
For television applications, the Advanced Television Bt.13591 Committee recommends that audio should lead video by no more than 15 milliseconds and audio should lag video by no more than 45 milliseconds.
SMPTE standard ST, published in provides technology to reduce or eliminate lip-sync errors in digital television. The standard bt.1395-1 audio and video fingerprints taken from a television program.
has been cited by the following article:
The fingerprints can be recovered and used to correct the accumulated lip-sync error. When fingerprints have been generated for a TV program, and the required technology is incorporated, the viewer’s display device has the ability to continuously measure and correct lip-sync errors. However, these timestamps are often added after the video undergoes frame synchronization, format conversion and preprocessing, and thus the lip sync errors created bt.13591- these operations will not be corrected by the addition and use of timestamps.
The Real-time Transport Protocol clocks media b.1359-1 origination timestamps on an arbitrary timeline. A real-time clock such as one delivered by the Network Time Protocol and described in itu-t Session Description Protocol  associated with the media may be used to syntonize media.
A server may then be used to for final synchronization to remove any residual offset.
From Wikipedia, the free encyclopedia. Retrieved 30 May Retrieved 4 April Archived PDF from bt.135-91 original on 2 October Archived from the original on Cugnini, Aldo Sep 1, TV Technology, originally from Broadcast Engineering. Salmon; Andrew Mason January Retrieved from ” https: Audio to video synchronization.
Literal Audio-to-video sync Lip dub.