Audio/video sync. Little help please? - diyAudio
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Old 17th December 2011, 04:21 PM   #1
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Default Audio/video sync. Little help please?

Have posted this in a couple of home theater boards to no avail. Hope I can get a bit of enlightenment here.

My internal/external speakers are out of sync on my Samsung plasma. I've found quite a few posts on the internet dating back as far as 2004 up to the present dealing with this issue. What it seems to boil down to (if such information truly applies to this set) is that the digital audio feed to the internal speakers is delayed in order to compensate for the slight delay in digital video processing for proper sync. The analog audio outputs from the back of the set are NOT delayed to match the video. This has been a known and discussed issue for many years and it seems that the universal expectation is that consumers are not ever going to be using both at the same time... as well as an expectation that the consumer is using external sound processing up-to-date enough to include its own adjustable delay/sync processing. This is an important aspect to my question since i have no plans to invest in such in the near future.

So for someone, like myself, who would like to use the internal speakers and a simple external powered subwoofer, as well as external amplification for a hearing impaired member of the family, are there any fixes for this? Are there user adjustable settings anywhere that don't expose me to the risk of screwing things up royally or upsetting the sync between the internal speakers and the video?

The hearing impaired setup is using the feed from the back of the set. I've been doing so for a year now. I had no idea that what they were listening to was not perfectly in sync with the screen, but now that I've been investigating this there is noticeable echo when listening to the headphones and turning up the television volume. If that is the case then the headphones alone are not syncing with the video.

So anyone owning these sets connected to an external sound system that DOES NOT HAVE up to date audio sync processing has an audio sync problem they just have to live with? (it's admittedly minor but noticeable. And what the heck is the point of owning HD in the first place if you're going to settle for inferior sound sync???)

Thanks so much for anything on this.
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Old 17th December 2011, 07:20 PM   #2
PRR is offline PRR  United States
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> compensate for the slight delay in digital video processing

You need a delay. I remember doing this with tape, with garden-hose, and then with BBD chips. These days digital audio delay is trivial. So trivial that you rarely see it sold stand-alone.

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DeltaLab DD1 Digital Delay Guitar Effects Pedal at Musicians Friend

This should work. Leave Repeat at zero and take off the knob. Adjust Level for about unity gain through, take off knob. Now turn Time until tap-dance comes-together on TV set and headphones at the same time, mark for reference.

This runs on 9V batt and will probably drain overnight. The "1 Spot" power adaptor is highly-regarded, overkill for this job, but only $20.

There used to be stereo digital delays with numbers on them. Often patched into studios. These days PC/Macs and ProTools do it without wires. The cheapest studio delay I found in a 60-second search was $500 new, but haunting studio forums and sites should turn up old DigiDelays under $99 stereo rackmount.

Since "theater inna box" audio can be bought not much over $99, these $59 and $99 (plus cables) approaches are not real attractive.

> what the heck is the point of owning HD in the first place if you're going to settle for inferior sound sync???

It's about having the biggest screen on the block. My big-TV sound sync is bad enough to bother me, but after years of counting sprocket-holes on movie-film and time-aligning concert halls, I just can't be bothered to care anymore.
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Old 18th December 2011, 05:05 AM   #3
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Thank you very much for pointing me in this direction. Elsewhere this unit was suggested...
Click the image to open in full size. 250 dollars. It's not much bigger than one of those effects pedals and req's a 9vdc adapter. Probably has just about the same circuitry inside! Has options to save settings and view the exact delay, but I'm only interested in correcting the grossest errors present in the setup and then tucking the unit away and forgetting about it.

For the time being this would work as well, no?
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I think the best way to go about this may be fiddle with that pedal unit until I eventually find a decent AV receiver at Goodwill. I'm not into surround sound, and the audio delay is the only feature I'd be looking for in an amp, so I can't justify buying new.

There's a pretty interesting couple of posts here that address this...

Last edited by peace brainerd; 18th December 2011 at 05:15 AM.
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Old 19th December 2011, 04:29 AM   #4
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PRR I'll look up the owner's manual for one of those pedals, but is your off hand feeling here that it might be a pretty straightforward wire-in? I mean, no real issues with inserting this device at some point between a television's analog audio output, external amplifier (if necessary) and speakers/headphones?

This one's 28 dollars, free ship, Amazon.. Would the "mode" dial be of any use in this case? Is that S for stereo, M for mono? What's the point of that if they all have A out and B out?
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Last edited by peace brainerd; 19th December 2011 at 04:39 AM.
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Old 19th December 2011, 05:03 AM   #5
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Screenshot of the owner's manual... this one has twice the delay range of the others, though 600ms is sure to be more than enough for syncing any audio/video problems.
Click the image to open in full size.

Should I be fine just connecting the television's analog audio output to the unit's in connector via 3.5mm to 1/4" TS adapter, and then likewise connect the OUT A and OUT B to an external amplifier's AUX inputs with 1/4 TS to RCA adapters?

Last edited by peace brainerd; 19th December 2011 at 05:05 AM.
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