[asterisk-dev] Asterisk codecs retranslation

Russell Bryant russell at digium.com
Mon Apr 23 08:37:41 MST 2007

Alexandr Olekhnovich wrote:
> I'm interested in one thing: as I know asterisk retranslates the media 
> stream with the next way
> 1. Gets the frame with the UA1's codec
> 2. Retranslates it to slan
> 3. Ratranslates slan to UA2's codec
> 4. Send the frame


> It seems to me, that it follows these steps anyway, the question is:
> Will Asterisk retranslate the frame ua1->slin->au2, if the codecs of the 
> 1-st user and the 2-nd are the same? I need him do not touch the frames, 
> just retransmit them as is.

In general, this is not necessary.  However, there are some cases where 
the frames still have to be translated into slin.  For example, if 
someone is listening to the call using ChanSpy, the audio in both 
directions must be translated to slin so that it can be mixed and then 
sent to the person listening.

Russell Bryant
Software Engineer
Digium, Inc.

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