[asterisk-dev] iLBC codec

[Klaus Darilion]

Am 13.07.2011 22:46, schrieb Hans Witvliet:
> On Wed, 2011-07-13 at 23:14 +0800, Steve Underwood wrote:
> 
>>> Steve Underwood schrieb:
>>> [...]
> 
>>> We had tested G729 vs iLBC vs G711 directly with Cisco 69xx phones on 
>>> a Cisco Callmanager installation. We have let a couple of people 
>>> compare the codecs.
>>>
>>> All persons what have tested have told us that:
>>> 1. All of the people told us that G729 sounds worst of all
>>> 2. All of the people told us that iLBC sounds good
>>> 3. All of the people told us that G711 sounds good
>>> 4. Most of the people told us that G711 has the best sound
>>> 5. A few people told us that iLBC has the best sound
>>>
>>> ...
>>>
>>> So I have a different opinion about iLBC then you. But this is just a 
>>> personal opinion :) At least I will always use iLBC instead of G729 
>>> where possible.
>> You can argue about G.729 and iLBC, but If G.711 wasn't the very very 
>> very very clear winner amongst those, I wouldn't trust your testing 
>> methods. :-) As long as you filter away anything below about 200Hz, 
>> G.711 sounds close to uncompressed 3.5kHz bandwidth audio.
>>>
> 
> Considering quality against bandwith usage, from the mentioned list
> above, G711 should provide best quality. Although not mentioned, perhaps
> wide-band codecs might be able yo produce something better. (at a price)
> 
> Just one aspect is not considered in the comparison, what is the impact
> of latency or loss on the quality? Perhaps some codecs are more
> vulnerable than others to not-so-perfect connections...

It is not only the codec. The whole RTP processing is involved (jitter
buffers, packet reordering) and there might be other tricks as well (
error concealment: interpolating data ...)

regards
klaus