[linux-audio-user] voicemail?

M P Smoak smoak at mis.net
Wed May 25 12:47:11 EDT 2005

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.
> [snip]
> > 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?

> > what type file will it be that is easily platform
> > independent
> Ogg vorbis is quite portable. Don't know about the GSM tools.

Again thanks,

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