CamJam

CamJam is a webcam multiplexer designed for use with the FIRST Robotics Competition (FRC).

Overview

CamJam is a streaming camera server at its core. It publishes an HTTP endpoint for clients to consume. Currently, it only supports streaming in MJPEG format.

Installation

CamJam can be run on any *nix platform that is supported by the go build tool. However, it was intended to be run on a Raspberry Pi 3 that utilizes the Pi64 image. It is recommended that this hardware and image be the target platform for installation as it is the reference platform that CamJam is developed and tested against. The following instructions are based on this recommendation.

CamJam

Copy the camjam binary to /usr/local/bin:

$> cp camjam /usr/local/bin

Configuration File

CamJam will automatically look for its configuration file in the /etc/camjam directory.

If this directory does not exist, then create it:

$> mkdir /etc/camjam

Create/copy a the configuration file to /etc/camjam/config.yaml:

$> cp config.yaml /etc/camjam

Systemd

In order to start CamJam when the system it needs to be configured to run as a service. This is accomplished by defining a systemd unit file.

Copy the camjam.service file to /etc/systemd/system:

$> cp camjam.service /etc/systemd/system

Then enable and start the service:

$> sudo systemctl enable camjam
$> sudo systemctl start camjam

udev configuration

In order to guarantee that each camera is always available at the same device path, it is recommended to use udev rules to assign custom symlink for each device.

Example:

KERNEL=="video*", KERNELS=="2-1:1.0", SYSMLINK+="camjam_0"

In the above example, the rule uses the kernel device name and the kernel parent device name to assign the specified device path/location. The result in this case would be that the video device found at USB Bus 2 on Port 1 would be assigned the device /dev/camjam_0.

Note: An example rules file can be found in the examples directory.

Configuration

CamJam is configured using a YAML based configuration file. There are two main sections of this file, server and cameras. The server section configures all options related to running the server. The cameras section is a list of camera configurations. The options for each section are detailed below.

cameras is a list cameras

Server Options

Option	Description
address	Configures the ip address and port that the server listens

Camera Options

Option	Description
name	Name of the camera. This can be any value that is relevant
	to the user.
device	Path to the device. e.g. /dev/video0
format	Format of the image captured by the camera. e.g. MJPG
width	Width of the image captured by the camera.
height	Height of the image captured by the camera.

Example:

server:
  address: 127.0.0.1:8000
cameras:
  - name: Front Camera
    device: /dev/video0
    format: MJPG
    width: 320
    height: 240
  - name: Rear Camera
    device: /dev/video1
    format: MJPG
    width: 320
    height: 240

Build

CamJam can be built to run locally for development and testing purposes or it can be cross compiled to run on a Raspberry Pi 3.

Requirements

• Golang 1.8+
• GNU make
• dep

To compile for local machine:

$> make

To compile for Raspberry Pi 3:

$> GOARCH=arm64 make

The resulting binary can be found in the build directory.