From ghazi.nocturne at gmail.com Thu Sep 24 16:25:35 2020 From: ghazi.nocturne at gmail.com (Ghazi Triki) Date: Thu, 24 Sep 2020 17:25:35 +0100 Subject: [Freeswitch-dev] A question about 16 bit linearisation in mod_conference Message-ID: 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 From mike at freeswitch.org Fri Sep 25 15:23:06 2020 From: mike at freeswitch.org (Mike Jerris) Date: Fri, 25 Sep 2020 11:23:06 -0400 Subject: [Freeswitch-dev] A question about 16 bit linearisation in mod_conference In-Reply-To: References: Message-ID: 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 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 From krice at freeswitch.org Fri Sep 25 19:21:12 2020 From: krice at freeswitch.org (Ken Rice) Date: Fri, 25 Sep 2020 14:21:12 -0500 Subject: [Freeswitch-dev] A question about 16 bit linearisation in mod_conference In-Reply-To: References: Message-ID: 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 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 > > > _________________________________________________________________________ > > The FreeSWITCH project is sponsored by SignalWire https://signalwire.com > Enhance your FreeSWITCH install with disruptive priced SMS and PSTN services. > Build your next product on our scalable cloud platform. > > Join our online community to chat in real time https://signalwire.community > > Professional FreeSWITCH Services > sales at freeswitch.com > https://freeswitch.com > > Official FreeSWITCH Sites > https://freeswitch.com/oss > https://freeswitch.org/confluence > https://cluecon.com > > FreeSWITCH-dev mailing list > FreeSWITCH-dev at lists.freeswitch.org > http://lists.freeswitch.org/mailman/listinfo/freeswitch-dev > UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-dev > https://freeswitch.com