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PostPosted: Tue Feb 02, 2016 5:50 am 

Joined: Thu Mar 19, 2015 12:24 am
Posts: 76
Hello,

Is anyone using the synchronize FM transmitters feature of StereoTool ?

We have a main high powered transmission site and some low powered repeater sites for towns that are too hard to reach from the main site (ie: behind hills and mountains).

I would like to know more about how the feature works - does it listen for something in the stream that's delivered or does it use some sort of internet clock reference ?

Our remote (repeater) sites are not on high speed internet and at the moment they play a standalone version of the same audio which is played from the main transmission site. They are usually 1 to 3 minutes out of sync with each other so when you travel between towns and change frequencies you may sometimes hear the same song again or be skipped forward to miss the following content.

It would be great to hear how others are using this feature.

BeDazzler.


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PostPosted: Tue Feb 02, 2016 11:03 am 
Site Admin
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Joined: Mon Mar 17, 2008 1:40 am
Posts: 9500
Hi,

How can they be 1-3 *minutes* out of sync? How are you feeding them?

The synchronization feature basically keeps the delay between streaming source and output constant. So it doesn't require any cues in the signal itself, it will automatically compensate for difference in pre-buffering when opening a stream and differences in the exact sample rate of different sound cards.

You can hear it in action here (see help page for more info):
https://www.youtube.com/watch?v=PH1mUfvo7T8


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PostPosted: Tue Feb 02, 2016 7:57 pm 

Joined: Thu Mar 19, 2015 12:24 am
Posts: 76
Hi Hans,

Thanks for the reply.

The repeater nodes run playout software that is the same as the main node, which then goes through ST before hitting the local repeater FM transmitter.

Whilst they all play the same playlist, because each node didn't start the hour at exactly the same time, sometimes they can be a few minutes behind or ahead of each other.

I have seen the YouTube video on ST FM Transmitter Sync and I see there are multiple transmitters carrying the same content, however I don't understand how they all play the same stream output at exactly the same time.

There must be some type of flag or marker that tells each ST installation where each ST computer is at.

How does each ST know how long to buffer or adjust the stream coming in ?

My use of that feature would need to be a little different in that we are not pulling a stream, instead we are playing an exact copy of the same program at separate locations via ST, so I need to find a way to sync / line-up the output at each node.

This is because some of the remote nodes are on 3G/4G type connections and we don't stream over mobile connections as it is not reliable.

Open to suggestions and ideas.


BeDazzler.


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PostPosted: Tue Feb 02, 2016 8:21 pm 

Joined: Tue Jan 26, 2016 11:34 pm
Posts: 54
Location: Jugoistočna Srbija
Is off-air reception possible?


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PostPosted: Tue Feb 02, 2016 8:26 pm 

Joined: Thu Mar 19, 2015 12:24 am
Posts: 76
No, too noisy. We tried it with custom receive antennas and boosters.

The problem with off-air feeds is when maintenance is performed at the main transmission site, power is sometimes turned down to 50% which would cause further issues at repeater sites.

Besides that, off-air feeds sound rubbish after being re-processed over and over.

All our sites have clean feeds with local DSP.

BeDazzler.


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PostPosted: Tue Feb 02, 2016 8:36 pm 

Joined: Tue Jan 26, 2016 11:34 pm
Posts: 54
Location: Jugoistočna Srbija
Stereo Tool has a filter for cleaning up FM hiss, so this may help.
From Stereo Tool help:
Quote:
FM Hiss (removes FM hiss from INPUT signal!) panel
Removes FM stereo hiss on the input (!) signal.

If you need to rebroadcast audio from another radio station, and reception is not optimal, this filter can remove the FM stereo hiss without touching the rest of the sound. The sound stays stereo. Even quite severe stereo hiss can be nearly completely removed.
http://help.stereotool.com/7.83/noise_removal.shtml


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PostPosted: Tue Feb 02, 2016 8:53 pm 

Joined: Thu Mar 19, 2015 12:24 am
Posts: 76
We've been there and done all that.

A spectrum analyzer was used to tidy up frequencies and get things sounding as good as we possibly could, but the shine just wasn't there.

We also tried MPX tuner equipment.

Local playout with full DSP works best.

BeDazzler.


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PostPosted: Tue Feb 02, 2016 9:21 pm 

Joined: Tue Jan 26, 2016 11:34 pm
Posts: 54
Location: Jugoistočna Srbija
I've ran out of ideas for doing anything that doesn't involve spending a significant amount of money.
Try streaming via mobile network on one of your transmitters, using off-air reception as a backup. Maybe it's more reliable than you thought.
Or set up an STL system between the transmitters? This can be expensive, especially when there is no optical visibility.


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PostPosted: Tue Feb 02, 2016 9:29 pm 

Joined: Thu Mar 19, 2015 12:24 am
Posts: 76
OK... thanks for that, maybe let someone else chime in with some ideas.

We have STLs for other locations where line of sight works, but as I said these are repeater sites where towns and communities are sitting behind very large mountains.

Even with 16dB gain antenna systems and high powered STLs we can't get past mountains.

BeDazzler.


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PostPosted: Tue Feb 02, 2016 10:48 pm 
Site Admin
User avatar

Joined: Mon Mar 17, 2008 1:40 am
Posts: 9500
The delay to different transmitters (different players) is usually nearly exactly the same for each transmitter (at least good enough to not notice anything when switching). And you can set an extra delay for each player if needed. So there is no need to add any marker to the signal.

Anyway, in your situation, unless you find a way to synchronize the playout systems, I don't see a solution.


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