Audio Compressing & Limiting via software.

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N9PBJ

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Aug 1, 2012
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San Antonio, Texas
Just wanted to throw this in here. I see in the wiki that someone described this method but said it was theoritcal. Since I'm using it actively I thought I'd just make a post on how I do it.

I'm utilizing two pieces of software:
Audio Compressor & Limiter by Stephan Hotto. (Audio Compressor & Limiter)
Freeware

and

Virtual Audio Cable (Virtual Audio Cable Home Page)
Apx $25 for a license. There is a trial version available that inserts a voice saying 'trial' in to the audio that you can use to see if it will work for you.

Instead of dedicating the primary audio card on the computer to the feed, I'm using a USB sound card that came with a Plantronics headset I used to use for Skype. The computer sees it as a C-Media USB Headphone. If you use a secondary usb sound card on this, make sure windows is set to still use your onboard card as your primary, or it will usually try to play sound / music out of the device that was connected last. You can set the default by (in windows 7) clicking on the speaker icon in the notification area and selecting playback devices. Then right click your onboard card and select 'set as default device'

The Scanner's speaker out connects to the mic in on the USB sound card via a standard 1/8" stereo to stereo cable. I then set the Audio Compressor & Limiter software to use the C-Media USB Microphone as the input, and the Virtual Audio Cable as the output.

ScanerCast RR edition then uses the Virtual Audio Cable as the input for the feed.

That's the fairly simple part. What's taken a lot of tinkering, and I'm still doing it, is tweaking the settings in the audio compressor and limiter software.

I've attached a screen shot of my current settings. I've basically used the same method described for the hardware in the wiki at Managing Audio Dynamics and Leveling - The RadioReference Wiki

Only difference is the limiter function. Only reason I have it turned to -9DB is to cut back the ear blasting alert tones for fire/ems dispatch. It doesn't effect voice at all so far.

Have said all that, I am still considering picking up a good used hardware compressor/limiter. With the addition of a new external antenna I may add a second feed and having two channels in the hardware would be nice.

So, hope it helps a little if anyone else is thinking of doing this. If you have any questions feel free to ask.

73's N9PBJ
-Dave
 

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CMaas

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Sep 3, 2011
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Location
Waupun, WI
Thanks for the information about your setup. I will have to try out that compressor/limiter.

I also am broadcasting my scanner feed and using the Virtual Audio Cable. It works great and doesn't seem to be noisy. The only difference I made is that I am using a program called VSTHost ( VSTHost ) that allows you to use industry standard VST plugins. There are countless free and not so free quality plugins to do this same thing.

The one item the program your using I wished had is a gate. I have a gate plugin that works great to silence any hum.

I am broadcasting using RadioFeed ( ProScan ) but only doing the web server at this time. It works great but seem that only Foobar 2000 (windows) and Stream Furious (android) work correctly with metadata. I would like to also to a RR feed but maybe down the road. The official RR android app seems wonderful.

Below is a screenshot of my audio processing. I am a audio tech as my side job so I am used to dealing with hardware solutions but software is just so easy in a application like this....plus a lot less expensive.

http://cmaas73.dyndns.org:8000/Server Info/VSTHost-2013-05-18.jpg

My stream page

http://cmaas73.dyndns.org:8000

I am a novice at broadcasting but it's been fun. I've had a scanner since 1993 but this has been a great way of bringing scanning to the 21st century

......sorry, hyperlinks did not work out on the links above.
 
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