DTV Audio Glitches

While no one can complain about the visual advantages of digital TV, the audio department is hearing plenty of complaints. The Dolby Digital standard does provide 'CD-quality' sound in the home, but other audio problems are plaguing the new format.

Loudness spikes and dips — you know, the annoyingly loud commercial break, or the extremely soft dialogue in your favorite drama cause people to keep a constant hold on the remote's volume control.

Even worse, lip sync problems make your local news look like a bad Japanese monster flic.

Is it your system creating the problem, or can broadcasters fix these problems?

Dolby Labs has ways to address the loudness problems. The standard employed in DTV broadcasts has loudness normalization parameters, but the problem is that program producers aren't using them. The system will work on everything from audiophile home theaters to old analog TVs to prevent spikes and drops, but it's just not being utilized properly.

The other problem is lip sync. You know how bad it looks when the sound and the video are out of sync. No offense to bad Japanese movies, but it looks like a badly-dubbed Japanese movie. For most people, the problem is most noticeable when the audio is ahead of the video. In nature, we're used to sound arriving later than what we see — sound travels slower than light. When it's reversed — when sound arrives before the visual, it just feels wrong and unnatural.

Any time a video signal gets processed, it can take longer to display than the audio, causing this problem in your home theater. The problem can occur in many places in the broadcast chain — from the satellite link to your local TV station, or when a video effect is added to a newscast, or even just from processing from your DVD or Blu-ray player.

TV broadcasters need to make sure there is absolutely no delay between audio and video when the signal leaves their hands, and every step in the broadcast chain needs to be checked. Home systems do have some control too, so make sure you haven't over-compensated for a problem that's already been resolved.

Digital TV is still a new technology, and it's just gonna take some time to work out all the kinks. Guess we don't really have a choice but to wait it out. —Leslie Shapiro

TV Newsday

Comments

[John M]

Digital audio is pitiful on DTV. Sync problems are the most annoying---seems like finally others are noticing and complaining---but not the only problem. The analog audio is LOUD; switch to the digital broadcast and you have to turn up the audio (amp) on the TV to the point where residual noise and hum in the TV audio amplifier becomes noticeable!!! So a great signal isn't worth squat if you introduce other background noise in the effort to have a reasonable sound level output from the audio amplifier. I have a portable unit with a DTV converter (tried several) and on digital I have to turn it to MAX output---never before a problem until the digital audio signal from the DTV broadcast.

[Earl B.]

We have a constant "hiss" or "static" noise in the background. Any idea what causes it? Don't seem to have a problem with the picture though--haven't paid any attention to the "synch" issue yet---just grateful to have the picture! EKB