[asterisk-dev] default format for sounds

[Tony Mountifield]

In article <48D6D487.6030109 at evaristesys.com>,
Alex Balashov <abalashov at evaristesys.com> 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.

There is already a degree of quantization loss in G.711. The highest
quality departure point would be 16-bit PCM with a higher sample rate,
ideally a multiple of 8kHz (or 16kHz for G.722).

I keep the masters of my own sound set as high-sample-rate WAVs, and
have a simple script that uses sox to produce 8kHz .wav, .al, .ul and
.gsm versions. Disk space to store them is plentiful nowadays.

It would be great if the same approach could become the default in the
makefiles.

Cheers
Tony
-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org