About the "dead air" in archive recordings...

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k7icu

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I can't seem to find a thread on this subject, but I suspect it's been discussed before.

A lot of audio archives for those not-so-busy feeds are mostly full of recorded silence. I doubt this has a huge impact on the size of the compressed audio files on the server, but it sure makes trying to weed out a short communication on such a feed challenging.

Has anyone on the server side of things looked into "voice activated" recordings, so the silence in between received transmissions is reduced to just X seconds?

I'm not a code jockey, but I'd be happy to help research a solution. I also have any necessary test equipment here to work with specific audio levels to help with testing, although I think both implementation and testing would be mostly done with software.

James K7ICU
 
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blantonl

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James, this is something that we are actively aware of.

From a server side perspective, it is a very CPU costly process to, well, process recordings to remove dead air. More expensive than just storing the dead air.

On the otherhand, there aren't any software solutions today from a stream recording perspective that allows us to mimic a vox process.

However, our team is looking actively at this and one day we'll probably get a solution...

Warm regards,
 

mtindor

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I can't seem to find a thread on this subject, but I suspect it's been discussed before.

A lot of audio archives for those not-so-busy feeds are mostly full of recorded silence. I doubt this has a huge impact on the size of the compressed audio files on the server, but it sure makes trying to weed out a short communication on such a feed challenging.

Has anyone on the server side of things looked into "voice activated" recordings, so the silence in between received transmissions is reduced to just X seconds?

I'm not a code jockey, but I'd be happy to help research a solution. I also have any necessary test equipment here to work with specific audio levels to help with testing, although I think both implementation and testing would be mostly done with software.

James K7ICU

It's better to download the audio and use a program (I am told there are a few out there) to strip the dead air from the recordings.

Keep in mind that if RR were to strip the dead air and only provide the active audio in the archive, there would be no way to identity more precisely where to find a specific item with that clip. many people who use the archives know what they are looking for, including the approx time that the event occurred that they want to review. When you keep the dead air intact, you are able to more precisely go through and find a specific event you are looking for if you know that audio was at a specific time.

For instance, you might have an agency that wants to review the audio from a call they were out on . they could request from 911 the audio log, but for things of lesser importance but still deemed important enough, the agency can just go to the archive and dig through and find the audio from that specific call.

Mike
 

k7icu

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A good point, Mike. I occasionally get to maintain big $$$ recording systems in a public safety environment so I definitely understand the importance of recalling a specific block of recordings based on a date/time. But I also think this is less important to the hobbyists here on RR, especially when archives are already split up into 15 minute blocks.

I figured this would most likely be a trade between drive space and a lot of CPU power. Here's to hoping a solution presents itself eventually...

In the mean time, can anyone recommend a Windows audio editor that can remove the silence? I just checked my favorite editor (Audacity), and it doesn't look like it can do it.

James K7ICU
 

GTR8000

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Audacity can indeed do it, the "beta" versions at least, not sure about 1.2.6 because I haven't used it in years, so I can't remember what the settings look like in that version. Import the mp3 file(s), then run Effect > Truncate Silence. The settings you can apply vary by release, I know they made changes in 1.3.8 since 1.3.7. Just be advised that there is a bug in 1.3.8 where if you have more than one track open and try to run the effect, it will copy the audio from the track above.
 

slingshot202

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Yup, AudaCity is the way. I use it now and have played with it to strip out dead air.

Pretty handy too! I am using 1.2.6
 
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