Synthetic camera publishers for testing rewire image converters.

Topics

Topic	Type	Description
/camera/image_raw	sensor_msgs/Image	RGB8 scrolling gradient
/camera/image_raw/compressed	sensor_msgs/CompressedImage	JPEG via image_transport
/camera/video	sensor_msgs/CompressedImage	H.264 Annex B stream (format: "h264")
/camera/depth	sensor_msgs/Image	32FC1 animated sine wave (0.3-10m)
/camera/depth/compressed	sensor_msgs/CompressedImage	PNG-encoded 16UC1 depth
/camera/camera_info	sensor_msgs/CameraInfo	Camera intrinsics
/tf_static	tf2_msgs/TFMessage	Static transform: map -> camera_optical

Setup

Requires pixi.

pixi install

This project uses pixi-build-ros to build the rewire_camera ROS package as a conda dependency. The ros-humble-rewire-camera (or ros-jazzy-rewire-camera) package is built from source and installed into the pixi environment automatically.

Environments

Environment	ROS Distro
default / humble	Humble
jazzy	Jazzy
kilted	Kilted
lyrical	Lyrical

Usage

pixi run app

In a separate terminal, run rewire to visualize in Rerun:

pixi run viz

app launches camera.launch.py. viz runs rewire record with config/rewire.json5 (all topics except /rosout and /parameter_events).

With custom resolution and frame rate:

pixi run app -- width:=1280 height:=720 frequency_hz:=10

Add -e <env> to pick a ROS 2 distro other than the default (humble):

pixi run -e jazzy app
pixi run -e kilted app
pixi run -e lyrical app

Development

After modifying the Python nodes in rewire_camera/, reinstall the local package:

pixi reinstall ros-humble-rewire-camera

How it works

The launch file starts three nodes:

• image_publisher - publishes synthetic RGB images, camera info, and a static TF (map -> camera_optical)
• depth_publisher - publishes raw 32FC1 depth and a PNG-compressed variant
• video_publisher - encodes the gradient plus a moving white square to H.264 (PyAV/libx264, zerolatency, no B-frames, keyframe every 30 frames) and publishes it as CompressedImage with format: "h264"

Testing VideoStream

The bridge maps CompressedImage with an h264/h265 format to Rerun's VideoStream archetype (rewire 0.7.0 or newer; on older releases build the bridge from source):

pixi run app
# other terminal
pixi run viz

/camera/video appears in the viewer as a decoded video stream instead of individual images. Select the codec with the video_codec launch argument (h264, default, or h265).

Native decoding requires FFmpeg

The viewer decodes h264/h265 through the ffmpeg executable (5.1 or newer) found on PATH. Without it the stream shows a decoder error.

Smooth low-latency playback

FFmpeg's default frame threading buffers roughly one frame per CPU core, which adds about half a second of latency and makes the viewer flash a buffering indicator on machines with many cores. Fix it by pointing the viewer at a wrapper that enables FFmpeg's low-delay options. Create the wrapper (adjust the FFmpeg path to which ffmpeg):

printf '#!/bin/sh\nexec /opt/homebrew/bin/ffmpeg -thread_type slice -flags low_delay "$@"\n' > ~/.local/bin/ffmpeg-lowdelay && chmod +x ~/.local/bin/ffmpeg-lowdelay

Then in the viewer open Settings, enable Video: override FFmpeg path, and set it to ~/.local/bin/ffmpeg-lowdelay (absolute path). This drops the decoder lag from ~16 frames to ~2 and works for both codecs. It also applies to video files, where it may slow down timeline scrubbing of high-resolution recordings; disable the override if that matters more to you.

H.265 open GOPs need viewer 0.7.0 or newer

Viewers before 0.7.0 (Rerun 0.34) only recognize IDR keyframes, so an h265 stream encoded with open GOPs (the x265 default) shows nothing for a viewer that joins mid-stream. Rerun 0.35 accepts CRA keyframes too, so from viewer 0.7.0 onward open GOPs work and video_publisher no longer forces no-open-gop=1. Two things still matter for any encoder: repeat the parameter sets on every keyframe (repeat-headers=1 for x265), and expect up to one keyframe interval of black after joining mid-stream before the picture appears (x265 defaults to keyint=250). If you must support older viewers, encode with no-open-gop=1.