[asterisk-dev] iLBC codec

[Steve Underwood]

On 07/13/2011 10:32 PM, Artem Makhutov wrote:
> Hello,
>
> Steve Underwood schrieb:
> [...]
>>> The main benefit of iLBC codce is that is has a _MUCH_ better audio
>>> quality then g729 and still requires pretty low bandwith and you do
>>> not have to pay license fees for using ilbc...
>
>> iLBC actually sounds a little worse than G.729, despite running at twice
>> the bit rate. What you have probably experienced is the effect of
>> chaining a cell phone codec with G.729 and iLBC. Any chaining of
>> multiple low bit rate codecs produces horrible results, but G.729 + cell
>> phone is far worse than G.729 + iLBC. This can make it an interesting
>> option.
>
> 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.
>
>>> I am using ilbc and I would like to see it in asterisk core. It is
>>> pretty annoying to compile it manually every time...
>> People complain about the CPU load of the open source iLBC. If you are a
>> serious user, have you ever looked into whether someone might speed it
>> up for you?
>
> I think that you are right here. I am just a hobbyist in the Asterisk 
> area and my "productive" Asterisk systems have never more that 3 
> simultanios calls :)
>
> Optimization of the codec might be pretty usefull but having an option 
> for ilbc transcoding in asterisk core without manuall compilation is 
> usefull too.
>
> Regards, Artem

Steve