Film-Tech Forum ARCHIVE: Sound Delay

This is topic Sound Delay in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Jay Glaus (Member # 6011) on 04-02-2016, 01:32 AM:

I have never had this happen before and perhaps someone can explain it to me. Had a customer tell me the film sound track was out of sync with the movie. I watched about 10 minutes of it listen to field speakers and my radio and it seemed fine. While I was watch customer came over again and said see it's doing it again. We then went to his truck which I believe is a Ram and listened and sure enough the sound on his truck speakers was about 5 seconds behind the movie. There were two cars parked on either side with their windows down and I listened to their speakers and it was fine. Only this truck was having a problem. I then brought my truck down which is a 2015 Ford with a touch screen radio and it was fine. I am sure there is nothing wrong with my Barco/GDC equipment but I never experience this before and wonder could this be a problem with newer models.

Posted by Jack Ondracek (Member # 1466) on 04-02-2016, 02:45 AM:

I haven't seen anything like what you experienced, but you can't have one radio be fine, another not and have it be your fault. As far as delay in your system is concerned, it goes out right... or not... for everyone.

Would have been interesting to have some time to play with that one.

Posted by Carsten Kurz (Member # 5396) on 04-02-2016, 05:09 AM:

What type of a radio was that? Sure 5s must be very annoying. Would have been interesting if you had tuned to a normal radio station with both and checked again.

I could imagine that some more recent radios apply digital processing which will introduce some latency. But 5s?

- Carsten

Posted by Harold Hallikainen (Member # 5405) on 04-02-2016, 09:52 AM:

It MIGHT have been a digital radio (IBOC or "HD" radio). This system in the US currently transmits digital sidebands on some stations in the channel adjacent to the analog transmission. When the error rate on the digital gets too high, the radio switches back to analog. To minimize the sound of the switch, the digital and audio are synchronized. The digital demodulator probably needs several seconds of signal to properly demodulate, so the analog also needs to be delayed the same amount. I'd think that they'd get rid of the delay if there are no digital sidebands, but maybe not. I'll check with my radio friends on this.

Harold

Posted by Jack Ondracek (Member # 1466) on 04-02-2016, 12:23 PM:

Hi, Harold.

Is it not true that HD stations insert the analog delay prior to the transmitter?

I wasn't aware that the receivers might be doing this as well.

In any case, drive-ins aren't transmitting HD, so there's no reason for a receiver to delay anything. I don't know any owner who feels having HD would bring enough benefit to the table to pony up for the Ibiquity licenses and exciters (per screen!).

Then, your server would have to feed audio to the system, several seconds ahead of the video, so the HD encoders have time to do their work. Someone correct me if I'm wrong, but I didn't think the servers could get that far ahead.

I'm really hoping this is just some fluke. We have a lot of HD stations in my area, though not many receivers. I haven't run into this problem at my place.

Posted by Harold Hallikainen (Member # 5405) on 04-02-2016, 02:07 PM:

True, it makes more sense to delay on transmit side. I will check further.

Harold

Posted by Randy Stankey (Member # 64) on 04-03-2016, 09:58 AM:

If the direct line from the field speakers is in sync and four out of five radio receivers are in sync, logic leads us to believe that the problem lies in the fifth radio receiver.

If this was an ongoing problem, I feel certain that there would have been a lot of customer complaints, by now.

It seems to me that there is some kind of analog-to-digital signal processing going on in that one radio receiver that is causing a delay.

The first thing I would look for is to check and see if there is some kind of digital enhancement mode on that car radio.

If there is, I'd try to turn it off.

Posted by David Buckley (Member # 2600) on 04-03-2016, 03:36 PM:

Randy on the money.

But... where is it written on tablets of stone that radios have to be real time? Just because they always were....

Posted by Sam Graham (Member # 2889) on 04-03-2016, 04:59 PM:

Dodge-Ram-Chrysler uses this godawful radio called "Uconnect", and version 8.4a (2013 models or later) has a Replay feature that can cache up to 22 minutes of music or 48 minutes of talk radio.

Chances are they inadvertantly activated it.

According to the owners manual, the fix is to switch stations, which clears the cache, then switch back.

Posted by Jim Cassedy (Member # 4115) on 04-03-2016, 08:47 PM:

I've external digital EQ boxes that can add quite a bit of delay to the audio
signal. 5 seconds seems like a lot, but I suppose it's possible.

Posted by Jack Ondracek (Member # 1466) on 04-03-2016, 08:55 PM:

quote: David Buckley
where is it written on tablets of stone that radios have to be real time? Just because they always were....

Well, of course it's not. However, for a radio to work at a drive-in theatre, which was the point of this thread, it would have to be capable of real-time operation. Otherwise, the customer would need something else.

Sporting venues would be another place where inordinate amounts of delay could be an issue. In our area, the flagship stations for our major league teams have to turn off their profanity delays for the local broadcast... which infers a certain trust between management and the announcers.

Posted by Scott Norwood (Member # 30) on 04-04-2016, 08:37 AM:

I am curious about the suggestion earlier to try a different station. If it is an issue with the Ram's radio, then one would expect that all stations would be out of sync, not just the drive-in sound. It does sound like a processing delay or that recording feature mentioned earlier, though.

And is it just me, or have car radios just become awful in recent years? Not so much with respect to reception quality (though not all are good with AM), but with respect to horrid ergonomics and useless "features." Most notably, why did anyone think that a touch-screen interface was a good idea for a device that is intended to be used by a driver? Almost every recent rental car that I have had has used a touch panel instead of buttons/knobs, and the idea of needing to look at the front of the radio while driving in order to adjust anything seems terribly dangerous to me.

In any case, the people who design cars clearly do not go to drive-ins very often. Daytime running lights without an easy defeat switch are particularly hostile to the drive-in experience.

Posted by Jack Ondracek (Member # 1466) on 04-04-2016, 10:14 AM:

Another issue with the displays is that many of them can't be completely blanked. My Pathfinder will blank to gray, but you still have to cover it to eliminate the distraction.

For awhile, daytime running lights were the thing, and a couple of manufacturers decided the owners weren't smart enough to decide if they wanted them or not. For them, we'll hand out one of our rental radios. For the rest... we've built up quite a cheat sheet on how to shut lights off. It's rare that we can't get all the lights out, and I don't recall we've ever had more than one car out here at a time with the problem.

Otherwise, car radios aren't much of a problem at the drive-in. We've accepted our numbers aren't large enough to have much influence on anything, so we roll with what we get. We have more trouble with the higher-wattage sound systems they're putting in, while, at the same time, using the same (or smaller) batteries. We make good use of the 4 Costco jumper boxes we keep on-hand here!

Posted by Randy Stankey (Member # 64) on 04-04-2016, 12:22 PM:

There are Bluetooth devices that plug into the OBDII port on your car that let you use your iPhone, etc., to check your engine stats, readout trouble codes and change some parameters of your car's computer system.

One such device is called "Carista" but there are several others.
http://www.caristaapp.com/hardware/

One of the things it lets you do is disable/enable the back-up alarm in a Prius. It can allow you to alter the settings of the DRL and headlights or the behavior of the electric door locks. (e.g. Automatically lock when car speed is over 10 MPH.)

The available settings vary from car to car and manufacturer to mfg. but I'm sure that dash/radio lights is one of them.

Posted by Thomas Pitt (Member # 4322) on 04-20-2016, 03:38 PM:

Indeed, many newer amplifiers are 100% digital and actually need some time to process the signal before it's output. Even if you have an analogue signal going in, it may take a short time to process before coming out of the speakers.

Of course you wouldn't notice this if just listening to CDs or radio, but anything that has to stay in sync like a movie soundtrack will cause problems. I have a hi-fi at home that has a digital amplifier. If you turn it to standby while set to the Aux input, then turn it on again, the sound from the speakers will be delayed. I like to pipe the audio from my game system through the hi-fi speakers, and have to momentarily switch inputs to eliminate the lag every time I turn it on!

In my opinion something of the sort has happened with this customer's car radio as well. A Peugeot hire car's sound system had a noticeable delay in both live radio and sound streamed from a Bluetooth source.