[Asterisk-Dev] codecs pass-thru

[Steve Kann]

Jonne Kodu wrote:

> I wonder how * handles the frames in the following case, when a 
> sip-session between a client, my * and a sip-pstn-gw, is using the 
> same codec, e.g. ULAW, on both call legs.
>
> Does asterisk receive the ULAW frames and decode them to an internal 
> PCM, to code the stream to ULAW again, at the other side, OR does it 
> pass thru the RTP frames without touching the audio?


It doesn't decode/recode, but even if it did, the conversions are 
lossless.  It doesn't "pass through the rtp frames", though, just the 
audio payload from the frames; the frames are unpacked and repacked.

>
> I don't use any t or T parameters, so I don't see any purpose for * to 
> touch(decode and code) the audio in this scenario.
>
> Looking forward to get an explanation
> /J
>
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