[asterisk-dev] default format for sounds

[Maxim Sobolev]

For what it's worth, I would vote for signed linear (aka sln) as the 
master format to go with distribution, plus maybe some common 
low-bitrate, such as GSM, which could be generated at the compile time 
from the master format.

The reason why signed linear is that selecting u-law or a-law flavour 
would mean that the other one would suffer quality degradation (i.e. 
converting from u-law to a-law or vice versa), while conversion from 
signed linear into a-law or u-law is simple table lookup and should not 
affect performance.

Alex Balashov wrote:
> I would say ulaw is the most common denominator, as it seems to me that 
> G.711u is the most parsimonious and ubiquitous use case and G.711u is 
> the standard-bearer of native PCM.  A-law could also work.
> 
> Everything else is overly specialised.  There should definitely not be 
> much, if any transcoding involved for default scenarios.
> 
> The other thing is that if someone does want to convert all their 
> prompts and recordings to some other format more compatible with their 
> configuration, the prompts need to be of the highest quality possible as 
> a departure point for any conversion or transcoding.  G.711u/A are 
> uncompressed 64 kbps / 8 KHz streams.  Everything else is varying 
> degrees of lossy compression.  I definitely would not distribute those 
> recordings using a CELP or other intensely approximated codec.

Regards,
-- 
Maksym Sobolyev
Sippy Software, Inc.
Internet Telephony (VoIP) Experts
T/F: +1-646-651-1110
Web: http://www.sippysoft.com