[asterisk-dev] default format for sounds

[Pavel Jezek]

Tzafrir Cohen wrote:
> Hi
>
> The default format for sounds files is currently GSM. This is done in
> the interest of backward-compatibility. However it maens that by default
> we get sound of lower quality and with more work by the CPU.
>
> I think it would be nice to switch to a different format (by default).
>
> Switch to a different format rather than just enable a different format:
> I suppose that the point of using GSM is to save space. If you suddenly
> enable a new format, you lose that benefit.
>
> * Except those who actually use GSM, and will now have to pay extra CPU.
>   GSM encoding is more expensive than GSM decoding.
> * But I suspect that those are generally a minority, and most will
>   benefit.
>
> Which will be the default format?
>
> Possible contenders:
> 1. One of alaw/ulaw. A good balance of size and CPU load, assuming 8kHz
>    sample rate. This is a raw format and hence can be easily
>    concatenated.
> 2. slin. Does it actually give a better quality than alaw/ulaw? It takes
>    more space.
> 3. wav - Unlike slin, this is not a raw format, and hence can be easily
>    be played (tested) by other players.
> 4. slin16: If we don't want to assume 8kHz sample rate all over.
>
>   
imho, most people is using asterisk with sip phones over wan, so we need 
common low bitrate codec,
and it seems, that g729 will be optimal - good quality, require low 
bandwith and almost all hw phones support it (except free softphones)
PJ