[Asterisk-Users] RE: [Asterisk-biz] Asterisk as a Voice Conference Server

[Steve Kann]

Kanuri, Seshu (Company IT) wrote:

>Iain Barker Wrote:
>-----------------
>  
>
>>Our experience with over 10 or more participants 
>>in a single Asterisk conference was that quality 
>>degraded quite rapidly.
>>    
>>
> 
>Is this really true as there were many in this list 
>who had confirmed that they have used the conference 
>bridge for a lot more connections than what you have
>Suggested as the upper limit.
>
>Logically the conference bridge should work at the 
>same capacity as the number of calls Asterisk can 
>handle in a given configuration.
>  
>

No, that's not true at all, especially for meetme.

For each member in a meetme conference, asterisk needs to decode their 
audio, mix audio from every other member, and then encode that mixed 
audio. The mixing operation is O(n^2). It's much simpler than the 
encoding, but as the number of users goes up, it should become the 
dominant operation.

So, if you have N users in a meetme conference, you need to do (for each 
frame, more or less):

N decodes,
N encodes,
N*(N-1) mixes.

Where N = 100, that's 9900 mixing operations. If N were 200, that would 
be 39,800 mixing operations.

Also, if asterisk is just bridging calls, it's generally not also 
transcoding, so it's capacity to do simple things with calls is going to 
be much higher than it's capacity to conference, especially with meetme.

-SteveK

>Though your solution looks impressive and probably is
>the best for upto 30 simultaneous calls, I am more
>interested in knowing what it takes for Asterisk to be 
>able to handle the 100 channels I need to run 
>Simultaneously.
>
>Seshu Kanuri
>  
>

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