[Asterisk-Dev] Dev Meeting this week.

[Rich Adamson]

All of the comments below represent a "solution", and the problem has
yet to be identified. How about we identify the root-cause first.
(We've all measured lots of things that describe the symptom, but
I've not heard anyone truly identify the root cause.)

------------------------
> I don't think just software AGC is going to do it without significant
> loss of "resolution". The peak amplitude that I'm seeing on the recorded
> WAV files that appear in my e-mail is probably about 2-4% of maximum.
> Software amplifying this will result in significant noise and distortion
> because the S/N ratio is so low. (This still may be better than not
> being able to hear it at all when listening to your voicemail over
> PSTN).
> 
> I have no idea if the zap gain can be adjusted on the fly with the
> current driver implementation, or if it requires additional ioctl's or
> other fixes to make this work. 
> 
> I think tying a relatively fast acting software AGC to the hardware gain
> of the zap interface would be ideal. 
> 
> Stephan. 
> 
> -----Original Message-----
> From: asterisk-dev-bounces at lists.digium.com
> [mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of Steve Kann
> Sent: Thursday, April 21, 2005 10:40 PM
> To: Asterisk Developers Mailing List
> Subject: Re: [Asterisk-Dev] Dev Meeting this week.
> 
> 
> On Apr 21, 2005, at 10:31 PM, Stephan A. Edelman wrote:
> 
> >
> > I also consistently get voicemail recordings from a zap channel that 
> > are barely audible. The gain on the zap channel needs to be adjusted 
> > on the fly when a voicemail message is left. Perhaps, some fancy 
> > software AGC and companding (to keep the volume at say, 90% of the 
> > clipping level) in combination with predefined zap gain.
> 
> libspeex has a reasonably good software AGC implementation, in the
> preprocessor (you don't need to use the codec for this).
> 
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