[Freeswitch-dev] A question about 16 bit linearisation in mod_conference

[Ken Rice]

slin is a raw audio codec. its the base digital representation of the analog sound waves. 

Going to slin is required to actually mix the audio. You can’t for instance just add  a g729 frame to another g729 frame and expect to get intelligible audio out of it. 

Going from G711 to slin is very low cost translation, however opus, g729 etc can have much larger overheads going to slin for the mixing stage. conference frame rate and sample rate settings  also have a big impact there. Video is even heavier on cpu utilization for various reasons. 

Sent from my iPhone

> On Sep 25, 2020, at 10:20, Ghazi Triki <ghazi.nocturne at gmail.com> wrote:
> 
> Hello guys,
> 
> I have few questions regarding the 16 bit linearisation in
> mod_conference. Especially on those lines
> https://github.com/signalwire/freeswitch/blob/master/src/mod/applications/mod_conference/mod_conference.c#L665-L667
> 
> 1 - What does 16 bit linearisation do? And what it is technically?
> 
> 2 - Does it have an impact on the mixing quality?
> 
> 3 - Is it considered as a transcoding, an intermediate encoding between
> the input streams and the final output stream?
> 
> Thanks
> 
> 
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