[Asterisk-Users] Whats the best audio compresion format for the following?

[James Gardiner]

All in all, I was more hoping to get some words of wisdom from the more
worldly Audio Compression experienced people in regard of the question below
about what is the best way to store audio recorded with asterisk.

Ie, to keep the BEST possible quality asterisk can record but still getting
great compression.  And not having to use any real time compression formats.
(mp3, ogg, etc)

Thanks,
James
 

> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com 
> [mailto:asterisk-users-admin at lists.digium.com] On Behalf Of Anon
> Sent: Thursday, 15 April 2004 11:15 PM
> To: asterisk-users at lists.digium.com
> Subject: Re: [Asterisk-Users] VoiceMailBox wav file format in EMAIL.
> 
> On Tuesday 13 April 2004 12:12 am, James Gardiner wrote:
> > Hi all,
> > I am not sure if tis is a bug but..
> > Was learning about VM etc to see how it all worked, and I 
> noticed the 
> > following..
> >
> > In the default install, the VM system leaves 3 different 
> copies of the 
> > Voice message.
> > Size	filename
> > 13kb	Msg0000.gsm
> > 13kb	Msg0000.wav
> > 122kb	Msg0000.WAV  <- under UNIX we have case 
> sensitive file names of
> > course.
> >
> > I wanted to have a look at these files so loaded them into 
> SOUND FORGE 6.
> > This first thing I noticed was that the LARGER file is of 
> much HIGHER 
> > volume. Like it had been normalised to 100% The smaller was 
> file, when 
> > loaded into sound forge, did not load properly, only the first 2 
> > seconds loads.
> >
> > Can anyone explain these issues and why they exist?
> >
> > All in all, I was wondering what would be the best format for best 
> > quality but with still great compression.
> >
> > I want to archive all calls for a period of time with self expire. 
> > (For example dedicate 5 gig disk space to the last number of calls 
> > that can fit in the 5gig.) I want to store the best quality 
> possible 
> > but also make best use of disk space, so I can store for 
> even longer 
> > periods.  I was considering ogg but then is occurred to me 
> that GSM or 
> > other codecs designed for audio with this frequency response may be 
> > better. (But the GSM file above is not as clear as the WAV ones 
> > produced.)
> >
> > I was also wondering if the VM system when emailing the 
> audio can be 
> > setup to use something like ogg or MP3?
> >
> > Comments appreciated,
> > James Gardiner
> That is a very interesting observation I had not seen yet.
> 
> There are certainly a few ways to do this.  Here is an idea: 
> run a cron job that downsamples the WAV file using sox, then 
> compresses it, and deletes the redundant files.  Make sure to 
> have the cron job run during the least-busy part of the day.
> 
> Yes, it is a crude solution.  ;)  Yet it may get you by until 
> you get a better solution.
> 
> Anon
> 
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