[Asterisk-Users] ZtDummy vs Hardware

[Steve Kann]

Kristian Kielhofner wrote:

> Jean-Michel Hiver wrote:
>
>> I was wondering what could be pros and cons of ztdummy vs proper 
>> timer device (i.e. X100P).
>>
>> I am going to set up an asterisk server in europe (to do trunking, to 
>> save bandwith) and I was wondering if it'll be OK to get it going 
>> with ztdummy.
>>
>> Furthermore, I have only a 1024/256kbps PPPOE DSL link and I need to 
>> squeeze 12 channels through, I was wondering which codec would be 
>> suitable for this? Is g.729a going to be indispensable or can I get 
>> away with something like GSM?
>>
>> Cheers,
>> Jean-Michel.
>
>
> Jean-Michel,
>
> Ztdummy can be okay, but true hardware timing WILL be better. But, as 
> Rich pointed out, that 256kbps ADSL is probably going to hurt:
>
> 256 - 41 = 215kbps usable bandwidth (%16 PPPoE overhead)
>
> IAX2 trunking with g729: 40kbps
>
> each add. call: - 10kbps
>
> So, 215 - 40 - 110 = 65kbps
>
> You only have about 65kbps to spare, and all of this is based on ideal 
> (theoritical) conditions. I doubt that those 12 calls will sound okay, 
> or even work at all...
>
> But, you can always try!
>

You might do better with Speex ABR at 8kbps or 10kbps average bitrate; 
(or, speex vbr) At least with speex you have the knobs to turn to tune 
things a bit better..

(which led me to find a bug in the ABR settings for speex in * CVS..).

-SteveK