[Asterisk-Users] .gsm voice format

[Steven Critchfield]

On Mon, 2003-07-14 at 09:47, Scott Stingel wrote:
> Ok, thanks.
> 
> I should have asked this in the first place: what I'm really getting at is
> that I need to record (or convert) prompts in many languages.  I have a
> number of Windows based tools to do this.  I want to end up with prompts
> that asterisk can play with the least CPU effort, ie. without transcoding.
> Would this be the gsm format?  If so, it sounds like I should record in Wav
> format, 8-bit samples?  How to convert to gsm?

First learn sox, it will save you a lot of time dealing with format
conversions. Next record at 8bit 8k so that what you hear on the
speakers is the same as what will go out to the phone. Then realize that
if you record via PCM and let sox convert to whatever you like, you will
be well off.

The question about transcoding, if you are going to PSTN via a hardware
interface, then you might want to store your audio in alaw or ulaw
format, if it is VoIP then whatever codec you might use there, or again
alaw/ulaw so it is a one hop conversion. 
-- 
Steven Critchfield  <critch at basesys.com>