Tools for the ffmpeg_image_transport

This repository hosts code for handling data streams produced by the ffmpeg_image_transport.

Supported systems

Continuous integration is tested under Ubuntu with the following ROS2 distros:

How to install

From packages

sudo apt-get install ros-${ROS_DISTRO}-ffmpeg-image-transport-tools

From source

Set the following shell variables:

repo=ffmpeg_image_transport_tools
url=https://github.com/ros-misc-utilities/${repo}.git

and follow the instructions here

Processing rosbags

Extract an mp4 file from a rosbag

The bag_to_file merges the ffmpeg-generated packets from a rosbag into a file:

bag_to_file -b input_bag -t topic -r rate [-o out_file] [-T timestamp_file] [-s start_time] [-e end_time]

The rate determines the fps used by ffmpeg when producing the output. The video is not transcoded, so what you get is the original stream, just in a mp4 container. To get correct playing speed the rate must match the rate at which the stream was originally recorded.

The start_time and end_time is given in seconds since the epoch, like the times you see when using ros2 bag info.

For example the following line produces a file video.mp4 and timestamps.txt from a rosbag:

ros2 run ffmpeg_image_transport_tools bag_to_file -t /cam1/image_raw/ffmpeg -r 40 -b ./my_rosbag/ -e 1710085164.466

The timestamp.txt file has the following entries:

# packet no, pts, header_stamp  recording_stamp
0 0 1710085154473057750 1710085156001866724
1 1 1710085155950467594 1710085156024209913

A H264 packet typically corresponds to a frame so the packet number conincides with the frame number.

Extract frames from a rosbag

The bag_to_frames decodes the ffmpeg-generated packets from a rosbag into frames:

bag_to_frames -b input_bag -t topic [-o out_dir] [-d decoder][-T timestamp_file] [-s start_time] [-e end_time]

The frames are written to out_dir with the ros header stamps embedded in the file name. A suitable decoder is usually guessed from the encoding used in the packet, but you can specify a valid ffmpeg decoder by using the -d decoder option. For start and stop times and the timestamp file see bag_to_file.

License

This software is issued under the Apache License Version 2.0.

Any contribution that you make to this repository will be under the Apache 2 License, as dictated by that license:

5. Submission of Contributions. Unless You explicitly state otherwise,
   any Contribution intentionally submitted for inclusion in the Work
   by You to the Licensor shall be under the terms and conditions of
   this License, without any additional terms or conditions.
   Notwithstanding the above, nothing herein shall supersede or modify
   the terms of any separate license agreement you may have executed
   with Licensor regarding such Contributions.

Contributors must sign-off each commit by adding a Signed-off-by: ... line to commit messages to certify that they have the right to submit the code they are contributing to the project according to the Developer Certificate of Origin (DCO).