A NixOS module to stream video from the Raspberry Pi 4 Model B. The project is in a draft state and will probably remain there permanently. Only one particular set of hardware is supported; see the Hardware section. A number of problems have been revealed in the course of development. For some of them, workarounds were found and are described in the Problems section. Have fun!

Contents

• Hardware
• Software
• Setting up
• Usage notes
  • Detecting the camera
  • Making a snapshot
  • Video streaming with rpicam-apps RTSP mode (works)
  • Video streaming using the rpicam-apps TCP mode (works)
  • Video streaming via the Gstreamer module shipped with libcamera (does not work)
• Problems
  • Where to find device tree overlay sources for the camera?
  • Meson buildsystem does not detect boost on NixOS
  • libcamera Gstreamer plugin reports timeout

Hardware

• Raspberry Pi 4 model B
• Arducam camera sensor ov5647

Software

In this setup, the Raspberry Pi board runs NixOS, initially obtained by cross-compiling the installation image. This image is later replaced by natively switching the system to its own configuration, which is not published for security reasons. In this repository, we declare a few components related to the camera service and its dependencies. The entry points of this repository are:

• raspi-camera.nix - NixOS module setting up a simple camera broadcasting service.
• libpisp.nix | libcamera-raspi.nix | pricam-apps.nix - Nix build expressions for main dependencies

Setting up

Here is how to add the rapi-camera dependency to a third-party Nix system configuration.

Consider a typical flake.nix. To use raspi-camera, we add flake input [1], optionally link its nixpkgs [2] to what other inputs use. Next we add corresponding output argument [3] and finally include raspi-camera module to the system's configuration [4].

{
  inputs = rec {
    ...

    raspi-camera = { # [1]
      url = "github:sergei-mironov/nixos-raspi-camera";
      inputs.nixpkgs.follows = "nixpkgs"; # [2]
    };
  };
  outputs = { self, ... , raspi-camera } : { # [3]
    nixosConfigurations = {
      raspi = nixpkgs.lib.nixosSystem rec {
        system = "aarch64-linux";
        modules = [
          ...
          raspi-camera.nixosModules.raspi-camera # [4]
          ...
        ];
      };
    };
  }
}

Usage notes

Detecting the camera

$ cam -l
[0:01:07.881818018] [957]  INFO Camera camera_manager.cpp:316 libcamera v0.3.1
[0:01:07.988647665] [962]  INFO RPI vc4.cpp:447 Registered camera /base/soc/i2c0mux/i2c@1/ov5647@36 to Unicam device /dev/media4 and ISP device /dev/media0
Available cameras:
1: 'ov5647' (/base/soc/i2c0mux/i2c@1/ov5647@36)

Making a snapshot

TODO

Video streaming with rpicam-apps RTSP mode (works)

This is the preferred way which we encoded into the systemd streaming service.

Raspberry Pi:

rpicam-vid --width 320 --height 240 -t 0 --inline -o -  | cvlc stream:///dev/stdin --sout '#rtp{sdp=rtsp://:8554/stream1}' :demux=h264

Client:

ffplay rtsp://10.0.0.80:8554/stream1 -vf "setpts=N/30" -fflags nobuffer -flags low_delay -framedrop

Video streaming using the rpicam-apps TCP mode (works)

https://www.raspberrypi.com/documentation/computers/camera_software.html#tcp

Raspberry PI:

$ rpicam-vid -t 0 --inline --listen -o tcp://0.0.0.0:5000

Client:

$ vlc tcp/h264://10.0.0.80:5000

Downsides:

• Only one connection at a time
• Server crashes on disconnect

Video streaming via the Gstreamer module shipped with libcamera (does not work)

• https://github.com/raspberrypi/libcamera?tab=readme-ov-file#using-gstreamer-plugin
• Same here https://www.raspberrypi.com/documentation/computers/camera_software.html#libcamerasrc-gstreamer-element

Raspi:

export LIBCAMERA_LOG_LEVELS=*:DEBUG

export GST_PLUGIN_SYSTEM_PATH_1_0=/nix/store/wlrmb5096gyi5xswy79kn6lpaj2b8p19-gstreamer-1.24.3/lib/gstreamer-1.0/

sudo gst-launch-1.0 libcamerasrc ! \
     video/x-raw,colorimetry=bt709,format=NV12,width=1280,height=720,framerate=30/1 ! \
     queue ! jpegenc ! multipartmux ! \
     tcpserversink host=0.0.0.0 port=5000

Client:

TODO

Problems

Where to find device tree overlay sources for the camera?

In contrast to NixOS best practices, this repo includes a binary device tree overlay from the Raspberry Pi firmware repo. Where can one find the sources of this overlay?

Meson buildsystem does not detect boost on NixOS

A workaround in raspi-camera.nix

env = {
  BOOST_INCLUDEDIR = "${lib.getDev boost}/include";
  BOOST_LIBRARYDIR = "${lib.getLib boost}/lib";
  # Also required in addition to the above fix.
  NIX_CFLAGS_COMPILE = "-I${lib.getDev boost}/include -L${lib.getDev boost}/lib";
};

Related reports:

• Meson no longer able to pick up Boost

libcamera Gstreamer plugin reports timeout

Libcamera docs describe a neat way to run the streaming using Gstreamer alone.

Sadly, we see the TIMEOUT failures, similar to what is described in this raspi forum thread. Unfortunately, removing arm64bit=1 from the /boot/config.txt is not an option because NixOS only supports 64bit.

The workaround was to switch to rpicam-apps.