What is it?

[netham45]

tl;dr: What it is:

• An RTP audio router with mixing, equalization, channel mapping, timeshifting, with a a web interface and REST api
• An ESP32S3 firmware that allows a portable device to receive/send RTP streams to/from SPDIF and USB UAC
• A collection of apps and configurations for getting audio to/from PCs/devices

ScreamRouter

I've been working on ScreamRouter (https://screamrouter.net/) for quite a while now, I've learned a ton about a lot while doing so.

At the core the backend is a C++ Python extension that allows python to configure routes and set up mappings/configuration while the backend handles mixing/equalization/etc... in C++ for speed. It is a many to many source to sink router that can handle things such as stream duplication to multiple sinks. I've currently got it working with RTP streams.

On top of that is a FastAPI interface that provides a REST API for configuring and using the backend. This is also where the configuration is saved to disk and reloaded, and things such as mDNS discovery are handled.

https://i.imgur.com/YCAMXPR.png

Then for the frontend I am using ReactJS. I also have MP3 streams the user can listen to, as well as the ability to send low latency streams to browsers over WebRTC/Opus so basically anything with a modern browser can act as a sink for it.

https://i.imgur.com/dBR83HW.png

esp32-rtp

This is an evolution of what started as a satellite receiver for ScreamRouter. It has evolved into a standalone RTP source/sink that also still works with ScreamRouter.

https://i.imgur.com/7ZVX4C2.png

It can

• Take audio in over SPDIF (I wrote a software decoder using the esp32's RMT so no additional ICs)
• Send audio out over SPDIF
• Take audio in by acting as a USB UAC 1.0 device (works with PC/Android/PS5/Switch)
• Send audio out over USB by acting as a USB UAC 1.0 host to a DAC

It currently has mDNS discovery for other esp32-rtp devices as well as the ability to join multicast SAP streams, and it can advertise SAP streams to receivers such as PulseAudio, PipeWire, and VLC.

Windows App

I have developed a Windows app for ScreamRouter. It puts an icon in the start menu that allows user control of ScreamRouter. It is also capable of capturing both application-level and system-wide audio from Windows, as well as acting as a ScreamRouter sink as a playback destination.

https://i.imgur.com/YRQIhxC.png

Android App

I've made an Android app using a protocol I am in the process of shifting away from (Scream) that can act as a sink for playback. Capture/Source is not possible at this time.

Various other sources

I've also got various other sources for ScreamRouter, including:

• Pre-configured docker containers to use PulseAudio to send RTP out to ScreamRouter for Amazon Music, Spotify, and Firefox
• A linux CLI tool for sending PCM streams
• PulseAudio/PipeWire configurations
• HTTP URL playback
• HomeAssistant Media Player Extension

PCB

I've developed a PCB that has

• battery charge controller
• ESP32S3
• headphone output (support not yet implemented)
• TOSLINK input/output
• USB host/device (host powered by battery)

https://i.imgur.com/a6aUhF4.png

This PCB works with esp32-rtp to provide a wide array of solutions from portable listening to home stereo integration

Future plans

• Now that I have shifted the receivers to RTP and have proper timestamps I intend on creating a system for synchronizing playback. I have already implemented NTP as part of esp32-rtp and ScreamRouter.
• Add an 80w stereo output to PCB
• Add cleaner workflow for mapping one 7.1 stream to 8 individual receivers (already possible just really messy)
• Try to find people to help with UI/design
• Running JUCE plugins