vulcast-rtc

Native Rust library for realtime communication with Relay, handling:

• Controller input over WebRTC DataChannel
• Audio/video encoding over WebRTC transport (post-MVP)

What

• C++ library vulcast-rtc encapsulating a WebRTC client using MediaSoup
• Rust sys crate vulcast-rtc-sys exposing FFI declarations from vulcast-rtc
• Rust crate vulcast-rtc exposing high-level abstractions for vulcast-rtc-sys

Build

Native

I don't recommend building natively on the Raspberry Pi itself. I tried myself and it never finished.

cargo build

Cross-compiling

Only cross-compilation for armv7-unknown-linux-gnueabihf is supported.

1. Install cross-compiler toolchain for arm-linux-gnueabihf

You must use a toolchain that has a relatively old version of glibc (<2.32), such as Raspberry Pi GCC Cross-Compiler Toolchains (Buster) gcc 10.3.0 from https://github.com/abhiTronix/raspberry-pi-cross-compilers. The rest of these instructions assume you are using this toolchain.

2. Install Rust cross-compiler toolchain for armv7-unknown-linux-gnueabihf

# install rust cross toolchain
rustup target add armv7-unknown-linux-gnueabihf

3. Build a project using vulcast-rtc

Replace /path/to/cross-pi-gcc-10.3.0-2 with where you extracted the toolchain to.

# add cross-compiler toolchain to PATH
export PATH=/mnt/scratch/cross-pi-gcc-10.3.0-2/bin:$PATH
# set linker for cargo to use for armv7-unknown-linux-gnueabihf target
export CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER='\
	/path/to/cross-pi-gcc-10.3.0-2/bin/arm-linux-gnueabihf-gcc'
# set sysroot and platform defines for bindgen 
export BINDGEN_EXTRA_CLANG_ARGS='\
	--sysroot=/path/to/cross-pi-gcc-10.3.0-2/arm-linux-gnueabihf/ \
	-I/path/to/cross-pi-gcc-10.3.0-2/arm-linux-gnueabihf/libc/usr/include/' 
cargo build --example echo --target=armv7-unknown-linux-gnueabihf

Sample

The echo example will produce a dummy video feed and a silent audio feed, and print consumed data.

cargo run --example echo -- --signal-addr <signal-addr> --token <token>

Troubleshooting

WebRTC check fail 0 == adm->Init()

# Fatal error in: ../../media/engine/adm_helpers.cc, line 39
# last system error: 88
# Check failed: 0 == adm->Init() (0 vs. -1)

Install an audio server like PulseAudio.

SIGSEGV in pthread when using TLS

Probably because we also link pthread as part of WebRTC and there is a conflict.

Try using rustls instead of native-tls. If that doesn't work then just turn TLS off.

version `GLIBCXX_3.4.29' not found

Your cross-compiler toolchain uses an incompatible version of glibc. Try using one of these: https://github.com/abhiTronix/raspberry-pi-cross-compilers