[Asterisk-Users] G729 codec

[Steve Underwood]

Nope. The floating point vs fixed point thing is something that has no 
effect on the ordinary user.

It is a matter of the internal implementation of the codec, and the type 
of processors on which it can run. The only thing the ordinary user 
needs to know is that what is sent out and expected as input by these 
two codecs is the same.

Regards,
Steve


todd wrote:

> Steve
> Trying to understand the floating point vs fixed, forgive my ignorance.
> By floating you mean it can very depending on usage from 6.4kbps to 
> 11.8kbps; were as the fixed will be constant 8kbps?
> Thanks
> Todd
>
> ----- Original Message ----- From: "Steve Underwood" <steveu at coppice.org>
> To: "Asterisk Users Mailing List - Non-Commercial Discussion" 
> <asterisk-users at lists.digium.com>
> Sent: Wednesday, May 25, 2005 5:14 AM
> Subject: Re: [Asterisk-Users] G729 codec
>
>
>> Ivan Meic (Vox Mundi) wrote:
>>
>>>> Actually G.729A is a reduced complexity version, and G.729B is a 
>>>> version with silence suppression. The data rate while sending voice 
>>>> is exactly the same, although the quality of G.729B should be a 
>>>> little higher. However the average rate for B can be lower if the 
>>>> silence suppression is used. Right now Asterisk doesn't make use of 
>>>> that silence suppression, so it makes not difference.
>>>>
>>>
>>> Steve,
>>>
>>> Any Cisco gateway support two G.729 variants.
>>> They call them g729r8 and g729br8.
>>>
>> Those are versions with different bit packing. Cisco started using 
>> G.729 before the packing order was standardised. They guessed it 
>> wrong. They had to change. :-)
>>
>>> So I guess that Cisco never implemented a reduced complexity version ?
>>> Also as far as I understand there are 3 G.729 variants generaly used.
>>> The first version (G.729), Annex A and Annex B.
>>> Are they all compatible with each others ?
>>>
>> There are Annexes up to I. The earlier versions are fixed point, 
>> reduced complexity fixed point and floating point at 8kbps. These are 
>> all compatible. Later annexes add (if memory serves me correctly) 
>> silence suppression, assistance for packet loss concealment (some 
>> people say G.729 includes PLC. It doesn't. What it includes is some 
>> features to reduce how badly PLC works with it), the standard for bit 
>> packing, and additional bit rates of 6.4kbps and 11.8kbps.
>>
>> Regards,
>> Steve
>