Good afternoon Maciej and Ms. Cortelli, I can only provide very basic additional comments but this post caught my attention.
I use Zoom several times a week to attend religious meetings (which includes pre-recorded video and music as well as live speech) and noticed that Zoom typically offers a decent but not outstanding audio codec (I remember the number 24 but can't remember if that was KHz or Kbps). The information is available in the statistics panel during a screen share. If the audio is live then the clarity is scaled up/down and you can run into some very serious issues which would result in a sound that is not at all acceptable for music. The scaling is dynamic; it is based on the person's internet connection, what equipment they have etc, etc (and which way the wind is blowing). Other factors such as the load on Zoom's servers (which has nothing to do with you or your student) seem to also affect the quality but that is an anecdotal observation. To summarise; Zoom is not reliable enough in my opinion. During a meeting use the statistics information to see what quality the audio is being transmitted at. Also, Zoom uses noise gates (minimum thresholds for opening the audio channel), background noise suppression algorithms and a few other fancy tricks which are great for selective switching of videos and preventing audio feedback but not so good for music. Linphone has the advantage that it can use high bandwidth/high quality codecs (forced codecs, you can control it to a certain extent) as well as do the other things Zoom is capable of (primarily being able to push video along with the audio). You can connect microphones to the tablet/laptop/phone and achieve a nice audio feed through Linphone. But, however hard you try, I am not sure you will achieve a result as good as recording the audio with software local to the student. All codecs have frequency limitations (equivalent of high and low pass filters) and whilst this is not a problem for voice, it may be an issue for musical instruments especially those producing higher pitched notes. And some codecs look like they're wide band but it can depend on the configuration/setup of the system and endpoints as to whether or not you can use the full wideband capability. The easiest way I found to show it is https://developer.mozilla.org/en-US/docs/Web/Media/Formats/Audio_codecs#Opus Another suggestion I would make is to look at WebRTC. This requires more infrastructure but if lockdown doesn't end any time soon it might be a good way of achieving a better result. I am not sure if you are teaching as part of a school, as part of a group etc but there may be someone who can give you better advice on WebRTC and if it will work well with your situation. WebRTC also allows someone to connect to the meeting via a web browser and that likely makes picking up the microphone feed much easier. Kind regards Stuart On Thu, 17 Dec 2020 at 11:29, Maciej Morycinski <[email protected]> wrote: > Dear Ms. Cortelli, > > Your idea is wonderful, and maybe some company already created a product > that would suit your needs exactly. It would certainly make sense to > research that in professional music circles. > > However, when it comes to using a SIP phone such as Linphone, it is > probably the wrong tool for this particular job. > > Issue #1 is with the codec. Despite your impression re Zoom, it is not > possible at all to transfer sound across the Internet without using _some_ > codec. Zoom certainly uses a default one. > If it is possible to select Opus Wide using Zoom, that might work for you. > There are various codecs appropriate for different tasks, but most of them > are unsuitable for music, as many are specifically > meant for speech only. Opus Wide is one of few exceptions. > > This brings me to Issue #2: if the student is using a telephone, or > Linphone, or anything that has a phone number assigned, then their > telephone service provider could be only > allowing certain codecs. The codec that ends up being used is negotiated > between your phone and your service provider, as well as between the > student's phone, and their service provider, > and one of the codecs available on both ends is selected. So to make sure > it works, both you and the student would have to have ONLY Opus Wide > allowed in Linphone, and both service > providers would have to allow it on their system. Otherwise there would be > translation, and sound quality would be lost. > > Your student would need to have a high speed, low latency internet > connection. If the connection is over a cellular network, then anything > slower than LTE will not work properly, > due to high latency. If you use not only sound, but video as well, then > the demands on the network throughput would be much higher than for sound > only. > > Bottom line is that I think using VOIP for music lessons MAY be possible > using Zoom, but if Opus Wide is not available, a SIP system (Linphone + two > service providers) will likely not work > to your satisfaction. It is still worth trying, but for business reasons, > I would not see it as a commercially viable system. > > If I had proper resources and a company, I would create custom software > based on something like Network Audio System (NAS) but since I know nothing > about it, I will leave it at that. > > Maciej Morycinski > #204-5100 Capitol Dr > Burnaby, BC, Canada, V5B 4S7 > > +1-778-820-0182 <+17788200182> > [email protected] > ------------------------------ > > On 2020-12-16 2:28 p.m., Stéphanie Cortelli (mailing list) wrote: > > Hello, > > I'm new to Linphone and would like to use it for music lessons, where > audio quality is very important. > > [...] > > _______________________________________________ > Linphone-users mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/linphone-users > > _______________________________________________ > Linphone-users mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/linphone-users >
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