How to video conference in high-quality stereo using Jitsi Meet

Ross M Purves, 03.10.20

Abstract

High quality stereo playback is important when teaching or performing music via video conferencing. Jitsi Meet is a free, open source video conferencing tool which can be set up to facilitate the sending of high-quality audio in stereo. Unfortunately, Jitsi lacks the means of enabling these features from the standard web-based user interface. Instead, the initiator of a video call must append a series of configuration options to the Jitsi server address and room name as a ‘query string’. This technical note has been drafted in the hope that it might support musicians and teachers wishing to take advantage of these features of Jitsi. It is important to note that stereo sound using the steps outlined will only work with Firefox used on both the transmitting and receiving machines. This document is a work in progress and comments and corrections are welcome.

Introduction

High quality stereo playback is pretty important when teaching or performing music via video conferencing. It is therefore unfortunate that, by default, most common video conferencing/online classroom tools feature mono audio, heavily processed to prioritise clearer speech at the expense of high-quality music reproduction. Some commercial systems e.g. Zoom can be configured to improve on this situation.

However, Jitsi Meet is a free, open source video conferencing tool which can also be set up to facilitate the sending of audio in stereo. Further advantages of Jitsi include full encryption, no requirement for users to set up accounts and no time limits on conferencing sessions. Although Jitsi Meet can be downloaded for free and installed by anyone who has the technical knowledge and access to an appropriate server, it can also be accessed freely via https://meet.jit.si/. The following notes assume the use of this public Jitsi server, but could probably easily be adapted to a self-hosted installation.

The Jitsi suite of technologies has featured in a range of research studies into online learning (e.g. Hamilton et al, 2018; Andujar et al, 2020). It also recently received a positive review for its potential as an online music teaching tool during the pandemic lockdown (Mariska et al, 2020).

Jitsi supports high-quality, stereo audio but lacks the means of enabling these features from the standard web-based user interface. Instead, the initiator of a video call must append a series of configuration options to the Jitsi server address and room name as a ‘query string’. Unfortunately, comprehensive documentation regarding these features is not easy to find and users are also liable to fall foul of bugs related to some browsers’ implementation of streaming audio protocols.

This technical note has been drafted in the hope that it might support musicians and teachers wishing to take advantage of a free, open source video conferencing/streaming in their practice. Technical details are taken mainly from Jitsi’s sourcecode and from the many disparate forum posts discussing these issues. The latter confirm that there is an appetite for an open source, freely-accessible, registration-free video conferencing tool for sharing music in high quality stereo.

The most important thing to acknowledge straightaway is that stereo sound using the steps outlined below will only work with Firefox used on both the transmitting and receiving machines. No other browser will play back in stereo, nor will the Android or iOS Jitsi Apps. The reasons for this are touched on below.

Important: This is a first draft and much remains speculative - comments, corrections and further information are all most welcome. Please send these to r.purves@ucl.ac.uk.

URL arguments

The person instigating the Jitsi video conference should use the following URL query string to enable stereo audio.

https://meet.jit.si/ROOMNAMEHERE#config.disableAP=true&config.disableAEC=true&config.disableNS=true&config.disableAGC=true&config.disableHPF=true&config.stereo=true&config.enableLipSync=false&config.p2p.enabled=false&config.prejoinPageEnabled=false

Replace ROOMNAMEHERE with your selected room name for Jitsi.

Other people joining the stream do not have to use the full URL. They only need to use this part:

https://meet.jit.si/ROOMNAMEHERE

Important: the instigator must join the room first, i.e. before all others using the simpler form of the URL. If anyone else not using these URL arguments gets there first, the normal Jitsi defaults will persist and stereo play back will not be possible.

Getting stereo audio into Firefox

On Windows, stereo audio can be fed into Firefox using a virtual mixer/loop back utility such as VoiceMeeter. On Linux, the loop back functionality within Pulse Audio can be used. SoundFlower is a similar tool that should work on Macs, although this has not been tested. The output of the loop back or virtual mixer device should be selected as the audio input within the Jitsi web interface in Firefox.

Alternatively, tests suggest that a stereo microphone will also work directly with Jitsi, via Firefox. Successful tests have been undertaken a Zoom H1 portable digital audio recorder configured in USB stereo microphone mode and also a Microsoft Surface 3, which has a stereo microphone installed.

Other Important Caveats

• The solution outlined here will not solve latency problems. There will still be a delay between the transmission and reception of the audio/video. Those looking for lower latency audio solutions should look at other tools, such as JackTrip.
• Even on a really good connection there are occasional digital clicks and jitters, sometimes too a sense that the audio is slowing down for a moment
• Careful level checking needs to be undertaken on the host machine to ensure that the stereo signal does not distort on its entry to Firefox
• The experience of users in China may not always be optimal.
• Recordings of meetings made via Jitsi’s built-in Drop Box recording facility seem to be made in mono, even when the session is enabled using the stereo flags in the URL.
• Jitsi enables users to share meetings via YouTube. Although this is not something I have tested, there are reports on the web that the audio feed that reaches YouTube is mono, not stereo.
• In early July, the Jitsi development team introduced a ‘Pre Join Page’ for users to add a name that will be displayed to others, check camera and microphone settings and obtain the chat room URL to share with other participants. These appears to be a useful and innocuous change but my tests before and since this introduction suggest it may have broken the stereo facility. It seems that it is now necessary for the meeting host to override this facility when they access themselves. This can be done by adding an additional argument to the URL query string, as outlined below. Once the meeting has been set up in this way, stereo will work again – even for participants who continue to use the ‘Pre Join Page’ themselves.
• A recent Reddit post has suggested that some people are working on extending the Jitsi web interface to support some of functions outlined here.

Why does this only work with Firefox?

As noted, Firefox must be used on the transmitting and all receiving machines. Even if you configure Jitsi with all the URL parameters listed above, other browsers appear to sum audio to mono. Tests suggest that Firefox on Windows, Macs, Linux, Android, and IOS will all work fine. This feels like a considerable limitation in some ways (particularly if someone is using a corporate machine where they can’t simply install another browser). But on the other hand, it’s no more of an impediment that having to install clients for Zoom, Teams or Skype for other kinds of video conferencing.

Jitsi Meet uses the WebRTC protocol via the Opus codec. At present it seems that Firefox is able to make use of Opus in stereo but other browsers may not be able to do so. Issues have been raised about this with regards to some other browsers (e.g. see here for a bug ticket   for Chromium). Moreover, Jitsi does not support either Internet Explorer or Microsoft Edge, although some test users said they were able to connect to the stream using Edge on some Windows 10 computers (but heard the audio in mono all the same).

What do all the URL arguments mean?

As outlined above, there is no way to enable stereo from within Jitsi’s web interface. Instead, a series of arguments must be added to the end of the normal meet.jit.si server room name. These must start with # and then each argument is separated by &. It is possible there is some redundancy here. Further checks are needed to establish if any of the following can be dropped from the working URL argument string.

What’s still to be tested

• Does this work with sharing one’s screen?
• Does this work when using an encrypted meeting link?

References

Andujar, A. & Rodriguez, J.M.F (2020). ‘WhatsApp and Jitsi to Foster Student Engagement in an American-Spanish Telecollaboration Exchange’, in Andujar, A. (ed), Recent Tools for Computer- and Mobile-Assisted Foreign Language Learning. IGI Global, 60-78.

Hamilton, W. A. et al. (2018). ‘Collaborative Live Media Curation: Shared Context for Participation in Online Learning’. In Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems (CHI '18). Association for Computing Machinery, New York, NY, USA, Paper 555, 1–14.

Mariska, B, Agster, S, Holmes, E & Stodola, H (2020). Comparing & Contrasting FREE Platforms and Procedures for Online Music Instruction: Skype, Zoom, Hangouts Meet, WhereBy, Facetime, Jitsi, etc

Acknowledgements

Thanks to all the individuals who helped me test different browsers and operating systems. I couldn’t have put these notes together without you.

Thanks as well to the fantastic team that have produced the Jitsi software. You have created a wonderful product for everyone to use.