Disable call knocking

[Malte Gerth]

Hi,

is there any way to disable incomig calls to knock if the user is currently active on another call and return busy instead?

Thanks in advance,
Malte

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[Stéphanie Cortelli (mailing list)]

Hello,

I'm new to Linphone and would like to use it for music lessons, where
audio quality is very important.

So, I would like to know how best to configure it for music.

1) Is it possible to deactivate all audio codecs, in order to transmit
the original sound (similar to Zoom which offers this option)?

2) If I use the audio codecs, in order to have the highest quality must
I use OPUS with bitrate of 128 Kbs? And is it possibile to disable all
the other codecs (speex, PCMU, PCMA, G729 which are enabled by default)?

3) Is it possible to make a test call to hear a short record of the
audio quality?

I have a very good Internet connection (optic fiber FTTH, 100 Mbps in
upload und 700/900 Mbps in dowlonad) and use Linphone under Linux 64-bit
(Debian Buster).

I also write a wish, it would be nice if in one of the next releases of
Linphone it will be possible to manage also a reverb filter and an
equalizer, the world of music lessons is constantly growing up and these
possibilities would make Linphone the perfect software. There are some
open source audio filter available, may be could they be integrated into
Linphone?

For example, I play the viola, and with all the string instruments
(violin, viola, cello) the best results are usually obtained with a
special microphone to be installed near the bridge (where are the
strings), however the sound captured in that position requires a (small)
reverb effect and the elimination of unwanted noise.

Thank you very much for your advices and sorry for my bad English.

Best regards,

Stephanie


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[Maciej Morycinski]

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.

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.

[...]

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[Stuart Elvish - STU Tele.com]

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 <[hidden email]> 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

<a href="tel:[phone]" target="_blank">[phone]
[hidden email]

---

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.

[...]

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[Stéphanie Cortelli (mailing list)]

Good evening and thank you very much to all for the answers!

Now I start to understand better, I didn’t know that the SIP server also affected the audio CODECS possibilities. I don't know if Linphone SIP free account supports Opus Wide, I hope yes.

I have initially thought to Linphone or Jami, the possibility to choose the bandwidth of Linphone is very nice, but now it seems me from your answers that a WebRCT based situation such as Jitsi could perhaps be the best for music, I also saw that there is a service, currently in beta, based on Jitsi and optimized for music: https://sirius.video/ I'm curious to try it out.

Searching on the web I also read about a use of Jamulus, which however requires the server Jack, for the audio together with a software like Jitsi or similar for the video.

I have to do some tests, at this point I should perhaps start from Jitsi or maybe from Sirius, which is already optimized for music, before thinking about software on SIP protocol.

Thank you again and best regards,

Stephanie

Il 17/12/20 03:13, Stuart Elvish - STU Telecom Inc ha scritto:

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 <[hidden email]> 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

<a href="tel:[phone]" target="_blank" moz-do-not-send="true">[phone]
[hidden email]

---

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.

[...]

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[hidden email]
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