Sync? What’s That?

Did you know that these cool new LCD and Plasma TVs add a delay into the video signal? Well, they do. I’m no expert but I would imagine it has something to do with converting the analog video signal to a pixel-based digital display.

If you take the cable out of your wall or a feed from your satellite dish and plug it straight into the plasma TV, and also hook up the sound to play through the TV speakers, you won’t have any problem. The flat panel TV will delay the audio and video signal the same amount and everything will stay in sync.

The problem occurs when you feed the video to your plasma or LCD TV and the audio to a separate receiver and speaker system. Because of this analog to digital conversion delay that happens in the video (which by the way does not happen on standard CRT televisions), the sound will appear to happen just slightly before the visual event. Try watching a live concert and you’ll really notice it.

Another way to see it is to send the same video signal–cable, satellite, DVD, or VHS–to a flat panel TV and to a CRT TV at the same time. Look for hard cuts from one shot to the next. The cut will happen a fraction of a second earlier on the CRT than on the panel.

I spent some time today at my friend’s house tweaking his new home theater that I’ve previously mentioned. His new 50″ Sony LCD Projection TV delays the video signal just like all flat panels do. Luckily his Denon receiver has a function where it will delay the audio signal on all channels to compensate for this. After a lot of testing with a Stevie Ray Vaughn concert DVD, we found that a 5 ms delay in the audio put everything in perfect sync.

Hopefully this information will help you make your home theater experience even better.