Volume High/Low Pass Filters, AGC filter

[Wes Miller]

I looked through the list returned by gst-inspect and in the list of all plugins on the website and I  don't see quite what I'm after.

First, Is there a stage to do volume pass filtering?  Idea is to sniff audio streams looking for low volume passages and replace them with silence or whitenoise af a fixed volume.  

Secondly, is there an audio AGC (automatic gain control) filter?  Following a 300 to 3000 Hz band pass filter and  an element that can do the volume pass operation, this element should clean audio (speech over noise mostly) to control highly variable background noise and maximize the speech quality.  Think of a microphone in use in an outdoor industrial setting where machines or heavy trucks start and stop continually.  First select only the usual voice band, flatten static, wind noise, motor/engine rumble, etc. then modify the overall volume to a pleasant level.

Yes, of course this would make more sense as a hardware process, but I though I might be able to use it to assist existing hardware or to augment a hardware solution.

Wes

[Gruenke, Matt]

I don't know much about the audio side of GStreamer, but I think I've
heard of what you refer to as "volume pass filtering" as squelching or
squelch filtering, in the context of two-way radios.  Also, RTP has a
concept of "silence suppression", "talkspurts", and "comfort noise".
Perhaps this information might aid you in your search for available
plugins, code snippets, etc.


Matt


-----Original Message-----
From: Wes Miller [mailto:[hidden email]]
Sent: Friday, January 07, 2011 15:10
To: [hidden email]
Subject: [gst-devel] Volume High/Low Pass Filters, AGC filter


I looked through the list returned by gst-inspect and in the list of all
plugins on the website and I  don't see quite what I'm after.

First, Is there a stage to do volume pass filtering?  Idea is to sniff
audio
streams looking for low volume passages and replace them with silence or
whitenoise af a fixed volume.  

Secondly, is there an audio AGC (automatic gain control) filter?
Following
a 300 to 3000 Hz band pass filter and  an element that can do the volume
pass operation, this element should clean audio (speech over noise
mostly)
to control highly variable background noise and maximize the speech
quality.
Think of a microphone in use in an outdoor industrial setting where
machines
or heavy trucks start and stop continually.  First select only the usual
voice band, flatten static, wind noise, motor/engine rumble, etc. then
modify the overall volume to a pleasant level.

Yes, of course this would make more sense as a hardware process, but I
though I might be able to use it to assist existing hardware or to
augment a
hardware solution.

Wes
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-AGC-filter-tp3193445p3193445.html
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[Stefan Sauer]

Am 07.01.2011 22:09, schrieb Wes Miller:
>
> I looked through the list returned by gst-inspect and in the list of all
> plugins on the website and I  don't see quite what I'm after.
>
> First, Is there a stage to do volume pass filtering?  Idea is to sniff audio
> streams looking for low volume passages and replace them with silence or
> whitenoise af a fixed volume.  

Replacing it with silence would be a noise-gate and I am sure there is one in
the form of a ladspa plugin. But then I am wondering, if you are actually
looking for a comfort noise generator?

>
> Secondly, is there an audio AGC (automatic gain control) filter?  Following
> a 300 to 3000 Hz band pass filter and  an element that can do the volume
> pass operation, this element should clean audio (speech over noise mostly)
> to control highly variable background noise and maximize the speech quality.
> Think of a microphone in use in an outdoor industrial setting where machines
> or heavy trucks start and stop continually.  First select only the usual
> voice band, flatten static, wind noise, motor/engine rumble, etc. then
> modify the overall volume to a pleasant level.

I don't think we have that one. Wanna try writing one? We have filters and e.g.
the level element. Mix well together and add whats missing :)

Stefan

>
> Yes, of course this would make more sense as a hardware process, but I
> though I might be able to use it to assist existing hardware or to augment a
> hardware solution.
>
> Wes


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