Embedded asterisk codec pass through


Concerning implementing asterisk on a NSLU2.

I see that asterisk needs to be slimmed and can’t “use” codecs like g723 or G729 ( I more interested in G723, although some sites says its outdated) . I am a bit confused by the “use” concept.

Is the intent of the meaning to say that a NSLU2 asterisk can’t transcode G723 or can’t use it all?

For example, if both sides are G723, isn’t this, concerning asterisk, just a pass through or am not i not understanding this correctly. If the (VOSP) Sip Server on one side used G723 and the ATA attached to the NSLU2 uses G723 natively, i should be able to “use” G723.

any comments woud be appreciated.

any comments on why asterisk needs to be slimmed would also be appreciated. If the NSLU2 is under unslung than can’t all the files be on a HDD or is the NSLU2 not up to the full task itself?


Yes, it can use G729 or G723 in pass through mode on NSLU2.
Transcoding is out of question because the processor has no float instructions.
I hope you realize that without the ability to transcode, lots of asterisk features will not work (voicemail, call transfer, etc).

Regarding slimming:
The NSLU2 has only 32MB RAM.
A reasonable approach is to load only the asterisk modules you are really using, otherwise you will end up wasting all the memory.
Personally, I was running Apache/PHP/gallery simultaneously with Asterisk, so memory was kind of tight.
Now, I have a dedicated NSLU2 running only asterisk 1.2.2 from a USB flash drive and it has about 5MB of free RAM. So, there is enough space to add more asterisk modules if required.

Please post you NSLU2 related questions to



followup re: G.723 @ 5.3/6.3kbps…

It is less bandwidth than G.729 @ 8kbps (these numbers not counting packet overhead that essentially bumps you to 3x these numbers) but you pay a big quality hit for the extra few kbps. Main thing is G.723 has larger payload sizes so is more impacted by any packet loss, and also it performs poorly if you have transcoding (which you will whenever features are implemented like voicemail, conferencing, music on hold, etc.).