[Freeswitch-dev] A question about 16 bit linearisation in mod_conference
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/mo... 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
The audio at this point is already singed linear (decoded audio), we add the samples then clamp then down to the range of the 16 bit sample. This is how you mix audio packets.
On Sep 24, 2020, at 12:25 PM, Ghazi Triki <ghazi.nocturne@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/mo...
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
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@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/mo...
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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participants (3)
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Ghazi Triki
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Ken Rice
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Mike Jerris