[Asterisk-Users] G729 codec

[todd]

Steve and all
Thanks for the education-

So there are limitations to what a specific codec can perform as far as 
platform it is running on?

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 4:55 PM
Subject: Re: [Asterisk-Users] G729 codec


> 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
>>
>
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