[linux-audio-user] voicemail?

Eric Dantan Rzewnicki rzewnickie at rfa.org
Wed May 25 14:27:22 EDT 2005

On Wed, May 25, 2005 at 12:47:11PM -0400, M P Smoak wrote:
> Thanks for your reply.
> On Tuesday 24 May 2005 15:58, anahata wrote:
> > On Tue, May 24, 2005 at 02:44:04PM -0400, M P Smoak wrote:
> > > In my work I use telephone in similar ways.  In both cases,
> > > phone calls are data.
> > > But it's too big.  Saving it as a .ogg file with quality = 4
> > > gets it down to about 5 meg, I think.  So the question is
> > > what's a good way to shrink it down?
> > For voice you could get away with a lower quality ogg and/or
> > resampling to a lower sample rate (digital telephony itself
> > uses 8kHz)
> Yes, I think I can use a lower quality ogg file or perhaps mp3.
> And I looked a bit at resampling.  Am I correct in thinking that
> it is good to record a high sample rate (say 44K), then normalize
> the recorded conversation, and then resample to a lower sample rate
> and save as an ogg or mp3?
> > For the ultimate in voce compression however, there are free
> > GSM compression/decompresison tools. In debian the gsm-utils
> > pachage seems to the the thing you need, no doubt will pull in
> > all the various libgsm* packages too. I haven't used it, but
> > if you can get it to do what you want you waon't get better
> > voce compression.
> You really lost me here.  gsm-utils package is for communicating
> with mobile phones.  We are using conventional telephones, with 
> linux being involved only for recording and saving the calls on
> conventional desktop/workstation machines.  Presently, I record
> using linux via rezound;  audacity could be used instead on 
> the prefessors Windows laptop.  Which linux/windows/mac recorders/
> players utilize gsm compression?

GSM is used to refer both to a system of communication for cellular
phone networks and to the voice compression codec typically used in
those networks. The gsm compression codec can be used independently 
from the cell phone network. 

Some quick googling found this:

But, again, I would also suggest looking at speex:

Eric Dantan Rzewnicki  |  Systems Administrator
Technical Operations Division  |  Radio Free Asia
2025 M Street, NW  |  Washington, DC 20036  |  202-530-4900
This e-mail message is intended only for the use of the addressee and
may contain information that is privileged and confidential. Any 
unauthorized dissemination, distribution, or copying is strictly 
prohibited. If you receive this transmission in error, please contact
network at rfa.org.

More information about the Linux-audio-user mailing list