satellite audio and video not in sync in chapel

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russellhltn
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#21

Post by russellhltn »

lajackson wrote:a 25" Sony television
Are we talking about a CRT or a flat screen? More to the point, is it a all analog set or does it have digital processing? If there's no digital processing in the set, then we have to look somewhere else for the delay.
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lajackson
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#22

Post by lajackson »

RussellHltn wrote:Are we talking about a CRT or a flat screen? More to the point, is it a all analog set or does it have digital processing? If there's no digital processing in the set, then we have to look somewhere else for the delay.

CRT analog. Old enough that you could not use it to pick up a digital signal off the air anymore. You would need a digital converter box.

It does have an onscreen menu system for settings and CC, etc. I guess that part is digital.
russellhltn
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#23

Post by russellhltn »

lajackson wrote:CRT analog. Old enough that you could not use it to pick up a digital signal off the air anymore.
I think we can eliminate the TV set as the problem. Something else - something digital - is causing a delay in the TV's feed.

I don't think it's the receiver. Not unless someone decided to avoid buying a audio distribution box and instead programed a spare set of outputs in the receiver for the same (English) channel.
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shanebankhead
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#24

Post by shanebankhead »

This is kind of an old thread, but I wanted to follow up on this since I just did some testing that I thought I'd share with you. As I mentioned in an earlier post, we have this problem in our building, and has continued to be an annoyance. It has been so bad on occasion that there have been several complaints from the audience, including the Stake President.

So, I finally had a chance to look into this a little more this weekend (conference weekend is usually my chance to clean up & fix equipment between sessions). Here's what I found.

As suspected, the culprit is clearly our projectors. I didn't have any test equipment available, but was able to get a pretty good idea of what was going on with a test recording on DVD. But I was surprised to find how much variation there was between our projectors. We have three different models of projectors, but they are all Sony, so I had expected they would have similar "engines", and have similar results.

One projector (the oldest model) had a delay of less than one frame (less than 33ms). The lip-sync delay is virtually undetectable with this model.

The "worst" one of the three had a delay of 3-4 frames (well over 100ms). This produces a very annoying amount of lip sync delay.

Anyway, this explains a lot, since we usually reach for the new projector first when doing a setup, which explains why the problem is usually there, but inconsistent. For a one-projector setup, our solution is easy- we'll just use the older projector.

But this doesn't solve our problem for multiple projector setups. I think what I'd like to try is add 50-60ms of delay to the audio line going from the satellite/production cabinet to the chapel. That way it will be closer to all three projectors and probably below most people's threshold of awareness.

This can be done by adding a delay unit. But I'm curious whether the main chapel mixer has the cabapility to do this. It is software based, and I believe it has some DSP capabilities, so maybe it's something that we can do within the current system without investing in new equipment? I'll be sure to ask our audio contractor (General Communications) next time I have a chance.

Anyway, I hope that's helpful,

-Shane
russellhltn
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#25

Post by russellhltn »

The first thing I'd do is disable as much processing on the projectors as I could. You may find that simply turning off a few menu items will fix the issue.
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shanebankhead
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#26

Post by shanebankhead »

I actually considered that and tried different settings on the projector. I think it helped a little. But it was hard to tell since my measurement method was kind of crude, and I couldn't measure subtle changes. But, it seemed like I was able to get that 3-4 frame delay down to less than 3 frames by trying different settings.

There was nothing I could do to get it down to an unnoticeable level.

From the research I've done, this appears to be a very common issue with home theater and commercial installations using newer projectors.
silid
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#27

Post by silid »

Is it practical to run the audio through the projector that is causing the delay and daisy chain the projectors together? Not ideal, I know.
russellhltn
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#28

Post by russellhltn »

SBankhead wrote:From the research I've done, this appears to be a very common issue with home theater and commercial installations using newer projectors.
If it's a common issue in home theater, then I'd expect there to be a simple solution. Otherwise the projector manufacturers will get black marks and slow sales.
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lajackson
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#29

Post by lajackson »

silid wrote:Is it practical to run the audio through the projector that is causing the delay and daisy chain the projectors together? Not ideal, I know.

At our location, we do not run audio through the projectors at all. Just video. Audio comes directly from the rack to the building sound system. It is possible that the combination of the VHS machine we are using for a tuner and the projector (that cannot cool itself and stay running for two hours, sigh) are inserting the video delay.

However, our very old televisions also have the delay, so it appears to be a difference between the audio processing and the video processing at the satellite rack.

And if we route the composite RF signal into a regular television, old or new, and the TV processes both the audio and video, the delay is still noticeable.
techgy
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#30

Post by techgy »

lajackson wrote:At our location, we do not run audio through the projectors at all. Just video. Audio comes directly from the rack to the building sound system. It is possible that the combination of the VHS machine we are using for a tuner and the projector (that cannot cool itself and stay running for two hours, sigh) are inserting the video delay.

However, our very old televisions also have the delay, so it appears to be a difference between the audio processing and the video processing at the satellite rack.

And if we route the composite RF signal into a regular television, old or new, and the TV processes both the audio and video, the delay is still noticeable.
We only use the RF signal in the chapel to pick up the ASL broadcast on a specific channel. We use a video output signal (No RF) for the projector and we've never noticed a delay. Is the delay on all audio channels (IE; other languages)? Do you have a video output w/o the RF?
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