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Audio - Animation Out of Sync


Sean Rizor

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I had to add some significant length to my audio RCA to my FM transmitter in order to cut back on RF possibilities. Last year was my first year and I found that by having my transmitter too close to my PC, the RF actually shut my computer down. Anyway, that's not the purpose of this post, but maybe this will be helpful to someone else. When I added the RCA length it caused a delay in my audio. So now my broadcast is less than a second late of my animation. How can I correct this? I cannot find any tutorials on this, but I slightly remember that the controller can be set to fix this problem. I might be wrong and possibly made this all up in my head. Can someone help me out with this?:?

Sean

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I can't say that I've ever heard of a case where adding cable adds that much delay. (Heck, I've never read where it's added *any*delay.)

What version of software were you running last year? Did you do any upgrades? Changed operating systems? Switch from MP3 to WAV (or vice-versa)?

I think those would be more of a culprit that the cable.

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I've upgraded everything that needs upgraded. If I switch the cable back the delay is gone. I have about 10 feet of cord there. The audio runs from PC through external sound card, to audio compressor, to mixing board and then to transmitter. All of those things were in place prior to the delay. I wanted to get the transmitter away from my pc a little more so added a large RCA extension. As I said, if I remove that extension the delay goes away. I don't want to take out the extension if possible. I can't explain why the additional cord causes delay, I can only try to correct it now.

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I would test your system with both cables and compare one more time. What you are describing really shouldn't be possible. Audio in a cable effectively travels at the speed of light, so for a 1s propagation delay to come strictly from the length of the cable, your cable would have to be roughly 75% of the distance from the earth to the moon.

Were you playing the same sequence with both cables? Perhaps if you're using different sequences, one is having a delay in software that you weren't noticing before. Just kind of shooting in the dark here.

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Let me see if I can give a good explanation here. I used the same sequence each time. So in an effort to try it without running it through the software I tried something different. I put a CD in and played it separately from the software and sequences. Then I turned on the stereo to listen to both the stereo and the PC sound. The delay is fairly noticeable. I would describe it as a form of echo.

Your knowledge of audio transmissions is obviously very good. When I describe the delay, I'm only describing what I hear from the PC to the actual broadcast. Maybe I'm just being too critical here. I spent some significant time in the radio business before getting into law enforcement. I make my own voice-overs and commercials. I have all the special software and effects. Sorry - I often get off track. My point is that I'm very critical of the audio. I have not actually tested the audio to a visual of the lights on the house yet. I just started getting everything put up. But there is still a noticeable delay in the audio with the extension. I wish that I could explain it. I'm going to play with it just a little more tomorrow.

I think if I spend any more time on it tonight my wife will have my head. In fact, I took this entire week off of work to get my lights done. I still have a lot of work to do. Thanks for the advice.

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Hmm. It's not totally unexpected to get a little bit of a delay with FM transmission. As you know the signal is being modulated one end and demodulated on the other end, and either the transmitter or receiver or both might might be using digital processing which, depending on the cheapness and/or complexity of it, might introduce audible delay. But you shouldn't hear any difference whether the cable between the audio source and the FM transmitter is 1 foot or 10 miles.

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Ok, well I will give it a whirl tomorrow and see how it fairs. I'm happy with the way the audio sounds. I have tweaked it about as much as I can. I'll try to report back after I've done that.

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Is the audio compressor analog, or digital? If digital, it will have far more delay than the cable will, and could easily account for the echo.

If the whole delay you are hearing is a fairly short echo, I don't know if you will be able to tell that the lights are off.

But, if they are actually off, you can use the skew track feature to shift the sequence around until it is back in sync with what you are transmitting.

Separately, the FM modulation and demodulation can both be done as completely analog processes. At the price point of the transmitters we are using, they are going to be analog, and I can't think of any audible delays that I would expect from the modulation and demodulation. But any random receiver may have some level of DSP processing, which can add some delay in there, which you have no control over. But, by and large, I don't expect it to be common in car radios, and I don't expect that it will be enough to be noticeable.

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The compressor is analog. But you raise a very good point. The receiver in my basement that is near my setup is digital. I haven't really tried it in my vehicle, but then I wouldn't know anyway because I would have no way to listen to it on my PC. I'm "really" pressed for time this year to get everything up and running. I made a few minor changes and added a mega tree and boy did that create me a headache. Now I have to move my sequences around to fit the changes.... huh....

Thanks for the insight on this. I will know more as soon as everything is up and running.

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