[Asterisk-Users] G729 codec

[todd]

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
>
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