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Audio Lip Sync - The Next Big Feature?

by August 30, 2004

Receivers that Help Your Audio and Video to Sync on Newer Digital Displays
In the "good ole days" of pre-HD CRT displays, audio and video processing took about the same amount of time resulting in almost no significant delay problems. Back then, no one had to worry about video taking longer to process than the audio that was being heard. Fast forward to HDTV and the era of video scalers, deinterlacing, and 2:3 pull-down and you are entering a time when video frequently takes longer than the previously 'acceptable' < 16.6 milliseconds (1/2 video frame, or one field in interlaced systems).

What Does it All Mean?

With the new digital televisions and improved video processing it is becoming more frequent to have fixed delays in video that make the audio appear to be ahead of the picture by as much as 4 frames (133.3ms). This is not to be confused with inherent delay problems coming from the cable or satellite company's transmissions (which can only compound the problem). In addition to this, some digital technologies, like direct view LCD televisions already have inherent delays of as much as 15-20 milliseconds, prior to any video processing. Some plasma screens even need to put data into internall memory before displaying picture, which can result in 20-60 milliseconds of delay.

Compounding this problem even further is the potential for varying delay times associated with what scaling or deinterlacing functions of video processing are engaged at any particular time (switching from 480p to 1080i inputs for example).
Mid-priced and higher-end displays already come with audio delay circuitry built in to match the audio and video signals and prevent lip sync. Unfortunately, many lower-end models do not, and even the higher end units do not account for the problems that occur when you route audio through a home theater processor or receiver.

Identifying the Problem

We have not yet thoroughly tested out the various setup DVDs to see if they address lip-sync issues as of yet, but you should be able to notice a consistent video delay where the audio appears to be ahead of the video picture. At the very least you should look at your screen and feel that something is "off". We'll be providing updates in the future with a means for accurately testing and addressing this issue once the proper tools for doing so (other than your eyes and ears) are confirmed.

How to Solve the Problem

Solving the problem will best be accomplished on the shoulders of the processor/receiver manufacturers. Since the video processing cannot be made faster (at least not until the technologies improve over time) the audio companies will need to provide a means of delaying audio to compensate. For now, a global lip-sync delay should be enough as most people onl have one monitor in their rooms (I won't be presumptuous at this point and take issue that some of us have projectors as well as HDTV televisions.) Look for at least 100ms delay capability. Here are some current manufacturers who provide lip sync delay for their processors and receivers:

  • Yamaha
  • Denon
  • Harman Kardon
  • Rotel
  • Arcam

Alternatively, DVD manufacturers can help the problem by providing players that have A/V sync options as well, though this is a less desired solution as it does not help with broadcasts originating from other sources. There are several manufacturers offering lip-sync delay on their DVD players.

Summary

This is a real problem, and one that is starting to rear its ugly head more and more as digital displays are gobbled up by the consumer (many of them towards the low-end pricepoints). Our suggestion to manufacturers is that they take this seriously and give the user easy access to lip sync delay right from a hard button on the remote control. This is something that needs to be easily accessed, and not hidden in a 7-layer menu system. With what we've seen from Yamaha (RX-V1400/2400 & Z9) and Denon (AVR-3805) and Harman Kardon (AVR 430/630) it looks like the manufacturers are on the ball and aware of this important issue.

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About the author:

Clint Deboer was terminated from Audioholics for misconduct on April 4th, 2014. He no longer represents Audioholics in any fashion.

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