[asterisk-users] Transcoding degradation G711<->iLBC

Tim Panton thp at westhawk.co.uk
Sun Apr 22 04:44:36 CDT 2012

I'm quite fond of GSM610 as a low(ish) bandwidth codec - although it isn't as good as (say) speex or Silk,
it is widely supported, and European users have had years of cellphone use to get used to the specific 
sound of a GSM call. So you can often go from a GSM610 supporting handset all the way through to a 
GSM supporting ITSP without needing to transcode at all.

If at all possible avoid creating a path which involves 2 different lossy codecs - e.g. 729 _and_ GSM 
the results are significantly worse than either.

If you can control all of the call path and have devices that support it, Silk is _lovely_ . It takes a bit of tuning
for your expected network (which is unfortunately manual in Asterisk 10) but it is worth it.


On 15 Apr 2012, at 12:15, Gustavo Garcia Bernardo wrote:

> Is it a good idea to use asterisk transcoding from G711 to iLBC or should I find out any other solution not involving transcoding (f.e. using G.729 that is supported in both sides).  I'm worried about voice quality and trying to avoid paying for G.729 licensing.
> Anybody with experience or quantitative measurements of the voice quality degradation in that scenario?
> Regards,
> G
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