Which Codec does PRI use?

Hi Guys,

We have an Asterisk 1.4.22 box with 2 PRI (5ESS). I’m using the server for IVR. There are a few IP phones used primarily for testing and when we go live, we will be strickly using PSTN.

I’ve recorded all of my system prompts in WAV format. Hard Disk space is not an issue but I would like to avoid having Asterisk do the Codec conversion “on the fly” for every call.

  • Could someone please explain if PRI actually uses a Codec?

  • Should I leave my prompts in WAV format or do a massive conversion before going live?

  • When a new prompt is recorded by a caller, should I record as WAV ?



Hi What country are you in ? if its US or japan then ulaw rest of the world we use alaw, Internaly depending on settings you may be transcoding via slin.

If you are going to be heavily using prompts then you might wnat to consider using a ram disk.


Hi Ian,

Thanks for your quick reply.

I’m in Canada, so it would be ULAW. But I didn’t know if PRI would use G711 or since it’s internal to the machine (no IP routing) if any codecs are used at all.

I do remember seing SLIN conversion CODEC errors when I was setting up my PRI.

How can I tell which one I am using ?



Can anyone please tell me which Prompt format I should use? Right now i’m using XXX.wav but I suspect I will be using the CPU to convert on every call.




Converting between linear and companded formats is very cheap. I would not worry about the conversion from 16 bit linear to 8 bit A or mu-law.