gscam2

ROS2 port of gscam. Supports ROS2 intra-process comms.

Update 15-Jun-22: gscam has been released for ROS2. It does not support IPC.

Update 16-Mar-21: the package name has been updated to match the repository name (gscam2)

Install and build

Tested on ROS2 Foxy, Galactic, Humble and Rolling. See the Dockerfile for install and build instructions.

Usage

Make sure your GStreamer pipeline runs successfully in gst-launch-1.0. For example, here's a pipeline that works for the Blue Robotics HD USB Camera:

gst-launch-1.0 -v v4l2src device=/dev/video1 do-timestamp=true ! queue ! video/x-h264,width=1920,height=1080,framerate=30/1 ! h264parse ! queue ! avdec_h264 ! autovideosink

Here's the same pipeline in gscam2:

export GSCAM_CONFIG="v4l2src device=/dev/video1 do-timestamp=true ! queue ! video/x-h264,width=1920,height=1080,framerate=30/1 ! h264parse ! avdec_h264 ! videoconvert"
ros2 run gscam2 gscam_main

Here's an example with parameters:

ros2 run gscam2 gscam_main --ros-args --remap /image_raw:=/my_camera/image_raw --params-file gscam_params.yaml -p camera_info_url:=file://$PWD/my_camera_info.ini

... where gscam_params.yaml is:

gscam_publisher:
  ros__parameters:
    gscam_config: 'v4l2src device=/dev/video1 do-timestamp=true ! queue ! video/x-h264,width=1920,height=1080,framerate=30/1 ! h264parse ! avdec_h264 ! videoconvert'
    preroll: True
    use_gst_timestamps: True
    camera_name: 'my_camera'
    frame_id: 'my_camera_frame'

Here's an example that uses a GStreamer tee to split the stream, with one stream producing ROS images and the second stream writing to MP4 files:

export GSCAM_CONFIG="v4l2src device=/dev/video1 do-timestamp=true ! queue ! video/x-h264,width=1920,height=1080,framerate=30/1 ! h264parse ! tee name=fork ! queue ! splitmuxsink location=video%02d.mov max-size-bytes=10000000 fork. ! avdec_h264 ! videoconvert"
ros2 run gscam2 gscam_main

There's a bug where the last MP4 file is not closed correctly.

Intra-process comms

IPC test -- CLI composition:

# First shell
ros2 run rclcpp_components component_container

# Second shell (ignore the deprecation warning, see https://github.com/ros2/ros2cli/issues/336)
ros2 component load /ComponentManager gscam2 gscam2::ImageSubscriberNode -e use_intra_process_comms:=true
ros2 component load /ComponentManager gscam2 gscam2::GSCamNode -e use_intra_process_comms:=true

Launch file composition:

ros2 launch gscam2 composition_launch.py

Manual composition -- handy for debugging:

ros2 run gscam2 ipc_test_main

Finding GStreamer plugins

GStreamer scans various paths for plugins and builds a plugin registry. The search process is described here.

gscam uses a parameter gst_plugin_path instead than the commandline option --gst-plugin-path. The paths in gst_plugin_path are searched last, not first.

If you have custom plugins you may need to override the plugin path. Here's an example showing how this works:

# Disable default locations
export GST_PLUGIN_PATH=""
export GST_PLUGIN_SYSTEM_PATH=""

# Provide the pipeline configuration
export GSCAM_CONFIG=videotestsrc pattern=snow ! video/x-raw,width=1280,height=720 ! videoconvert

# Run gscam_main, providing a custom plugin path
ros2 run gscam2 gscam_main  --ros-args -p gst_plugin_path:="/home/me/myplugins"

Parameters

Parameter	Type	Default	Notes
gst_plugin_path	string		Similar to --gst-plugin-path, searchs path for plugins
gscam_config	string		GStreamer pipeline configuration
sync_sink	bool	True	Enable GstBaseSink synchronization
preroll	bool	False	Transition to GST_STATE_PLAYING twice
use_gst_timestamps	bool	False	Use gst time instead of ROS time
image_encoding	string	sensor_msgs::image_encodings::RGB8	ROS image encoding
camera_info_url	string		URL to camera info file, e.g., file:///path/to/file
camera_name	string		Replaces ${NAME} in the URL
frame_id	string	camera_frame	Camera frame ID

Topics

• camera_info
• image_raw
• image_raw/compressed - only if image is encoded as a jpeg stream

Camera info file formats

Uses the ROS standard camera calibration formats. Files must end in .ini or .yaml.