Business Problem

The Symphony Media Bridge (SMB) is a media server application that handles audio, video and screen sharing media streams in an RTC conference system.

In RTC conferencing systems, when more than two participants are in a conference there is usually a media server component involved. Each participant in the conference will send their audio and video streams to the media server. The media server is then responsible for sending the correct media streams to each receiving participant.

Conferencing media servers are typically divided into two categories, multipoint conference units (MCU) and selective forwarding units (SFU).

MCUs decode, mix and transcode media streams delivering a single or a few output streams to each receiver.

SFUs do not decode or transcode media streams from participants, but forwards a selection of the incoming media streams to each receiver in some intelligent way. Not all incoming streams are forwarded, but typically more than one stream to each receiver.

Both types of media servers have their benefits and drawbacks depending on the use case, but that is outside of the scope of this document.

Proposed Solution

SMB is an SFU at its core, but has some hybrid MCU like solutions. Video streams are forwarded and not transcoded, but participants can request a mixed, transcoded audio stream instead of forwarded streams.

SMB can also be run in a mode where multiple streams are forwarded, but the contents of each stream can vary between different participants in the conference. This allows for larger conferences than SFUs can typically handle.

Written as a high performance native application with efficient resource management, SMB is designed to scale efficiently as the number of conferences and participants grow.

The main differentiators for SMB are:

It has a low CPU footprint and scales more efficiently when conference sizes grow. It is written in C++ with few third party dependencies and has a clean maintainable code base.
It has a new efficient receiver side bandwidth estimation algorithm unique for SMB that could possibly be beneficial to the WebRTC project.
It has a novel hybrid SFU/MCU mode with media stream rewrite enabling larger meetings than SFUs usually can manage.

Tentative Roadmap

Improve sender side bandwidth estimation to better handle degraded uplink network scenarios.

Current State

The project is in GA state and is used in production for Symphony Meetings.

Existing Materials

Current official repository: https://github.com/SymphonyOSF/SymphonyMediaBridge

Development Team

Olof Källander, Symphony, olof.kallander@symphony.com, olofkallander (Lead Maintainer)
Marcus Spangenberg, Symphony, marcus.spangenberg@symphony.com, marcusspangenberg (Maintainer)
Ricardo Domingues, Symphony, ricardo.domingues@symphony.com, RicardoMDomingues (Maintainer)
Pontus Carlsson, Symphony, pontus.carlsson@symphony.com, pcarlsym (Maintainer)
Rafael Berne, Symphony, rafael.berne1@symphony.com, rmberne (Maintainer)

What's next?

Upon submission of this project proposal, the FINOS team will get in touch with you to discuss next steps.

Contribution process (v. 1.0, last updated on October 2, 2020)

Below is the list of tasks that FINOS Team and the contribution author go through in order to complete the FINOS contribution process. Please do not edit these contents at contribution time!

FINOS Contrib POC

[x] Identify and Assign FINOS Project Coordinator - @Julia-Ritter
[x] Identify and Assign FINOS Strategic Advisor - @mindthegab

Kick-off meeting

[x] Set up kick-off meeting with project leads to review:
- [x] FINOS overview (if necessary)
- [x] FINOS Maintainers cheatsheet
[x] Discuss project proposal

Identify project meta (Lead: FINOS Contrib POC, Support: FINOS Marketing)

[x] Project Name - Symphony Media Bridge
[x] Category and sub-category (for FINOS Landscape) - Applications > Symphony Ecosystem landscape
[x] Existing code or new Github repository (see above)
[x] Existing code releases (and which artifact repositories are used) - 19, not public
[x] Team composition: lead maintainer and other maintainers
[x] Continuous Integration (existing/yes/no)
[x] Define project slug - SymphonyMediaBridge

Maintainers, contributors and CLAs (Lead: FINOS Contrib POC, Support: FINOS infra)

[x] For each maintainer identified in the previous step, collect: the following info:
- Fullname
- GitHub username
- Corporate email address
[x] Identify other existing contributors (assuming there's a contribution history (eg Git history)
[x] Check if maintainers and other contributors are all covered by FINOS CLA

Project Communication Channel(s)

[x] Ask maintainers which communications channels they'd like to use
Asynchronous
- [x] GitHub Issues (public)
- GitHub Discussions (public)
- GitHub Team Discussions (public and private FINOS CLAs Required)
- [x] Google Groups - symphony@finos.org
- [x] Add team to the mailing-list
[x] Link communication channels linked front and center in the project README.md

Code validation (only if code is contributed) (Lead: FINOS Infra)

[x] The codebase doesn’t have HIGH or CRITICAL CVEs across direct and transitive libraries
[x] The codebase doesn’t have any unfriendly licenses across direct and transitive libraries
[x] (optional - if a build system is provided) The build process runs successfully
[x] finos-admin is Admin of the GitHub repository to transfer
[x] The codebase doesn’t include any patent or copyright that conflicts with FINOS Governance and bylaws (to be validated with FINOS Legal team)
[x] Apply project blueprint contents - see ODP docs
- [x] README to adhere to FINOS template
- [x] LICENSE
- [x] Badge
- [x] Ensure that the proper project governance is in the CONTRIBUTING.md file
[x] All incubating criteria are checked and documented below

Approval (Lead: FINOS Infra)

[x] Assign issue to Executive Director (@mindthegab) to trigger voting
[x] FINOS accepts the contribution (and the contribution process can move forward)

Code transfer (Lead: FINOS Infra)

[x] Check GitHub repository transfer requirements:
- [x] finos-admin has Admin to all repositories to transfer
- [x] finos-admin ia allowed to transfer repositories out of the org
- [x] if the repository is owned by a user (and not an org), the user must be able to transfer the repository to finos-admin
[x] Transfer all code assets as GitHub repositories under github.com/finos
[x] Invite GitHub usernames to GitHub FINOS Org
[x] Create <project-name>-maintainers GitHub team and invite users
[x] Configure finos-admins and finos-staff team permissions
[x] Enable EasyCLA / CLA Bot

Infra setup (Lead: FINOS Infra)

[x] Update release coordinates and code namespace to include finos (best effort)
Enable security vulnerabilities scanning (This code base does not bundle dependencies).

Metadata update (Lead: FINOS Infra)

[x] Add project to metadata
[x] Add identities, orgs and affiliations to metadata
[x] Add logo to FINOS landscape
[x] Add project maintainers emails to finos-project-maintainers@finos.org list
[x] Add project maintainers GitHub usernames to the project-maintainers Team
[x] Onboard project on LF systems (SFDC, Insights, EasyCLA, Groups.io)
- SFDC issue

Announcement and follow up

[x] Work with FINOS marketing to send out announcement to announce@finos.org , checkout announcement template at https://finosfoundation.atlassian.net/wiki/spaces/FINOS/pages/83034172/Contribute
[x] Notify FINOS Contrib POC and FINOS marketing manager once the announcement has been sent out (FINOS infra)
[x] Update Landscape - merge https://github.com/finos/finos-landscape/pull/120

finos / community

Software Project Contribution and Onboarding - Symphony Media Bridge #140