Related / history: #q302472.

If the goal is to be able to pass this video to all types of ROS consumers then converting your datastream into sensor_msgs/Image would be the way to go. The "specific events" would probably need custom messages.

Conversion to sensor_msgs/Image would be up to you I believe, I don't know ..

.. of a library available that takes in videolink packets and converts it to camera frames. The msg structures for the events can be created using standard functionality.

As soon as you're using standard infrastructure, rosbag and other ROS nodes should be able to work with your data.

If your ..

.. goal is to use rosbags (ie: .bag files) to store your original data stream (so packet-per-packet) then please clarify. It could still be done (ie: create a custom msg for a videolink packet and store those), but there would be no compatibility with cv_bridge in that case.

Hi, thank you for your answer.To clarify, we're using Omnivision OV2775 and Sony IMX290 image sensors and images (video) is taken in HDR.Those sensors are commonly used in automotive. So, what we want is to store our original data in .bag and than be able to convert them into OpenCV compatible type

If you want to store data in its original format, then you'll have to create custom msgs that can encode that format.

Conversion to a ROS cv_bridge compatible format (I assume that is what you meant) would have to be done afterwards, by a tool you write yourself. Input would be ..

.. the .bag with the custom msgs, and output could/would be a .bag with sensor_msgs/Image (in any of the encodings supported).

Conversion could of course also happen live, and then a single back could contain both the original data as well as the converted data.

The problem is that we don't record our data using ROS, just store our data in .bag files using rosbag file format respectively. So, creating custom messages and converting them by writing our own tool would be inconvenient.

The bag format is message based (well, the typical interfaces to it anyway). I'm a little confused as to how you would store data in a bag without using messages.

Can you show an example how you write data to the bag right now without using custom messages?

https://drive.google.com/file/d/11ux3tsYEO9D-rCq2KwILWC3GvW8eFdcI/view?usp=sharing (made this for better visualization) These sensors are commonly used in automotive, so this image type is not strictly ours. We would like to propose to the comminity to create a format for these messages so they can

be widely used.

I cannot access your google drive without logging in.

I'm getting the impression you have two goals:

1. use .bag format to store your data in (for your product)
2. start a discussion about adding new standard msg types to ROS for automative sensors

Is that correct?

re: your last edit: working with ROS typically means working with msgs. These can be standard msgs (like from sensor_msgs) or custom messages.

Working with image data in ROS typically means converting whatever device-specific format you have into one of the encodings that sensor_msgs/Image ..

.. supports.

All frame-based cameras in the end capture frames. So that should be convertible to a sensor_msgs/Image.

If you don't want to do that, you can introduce a custom message that better captures the characteristics of your sensor data.

Perhaps you can clarify this:

we don't record our data using ROS, just store our data in .bag files using rosbag file format respectively

why do you record your data in .bag format?

Refering to your previous comment,that's correct: we want to use .bag format and in order to do that I started this discussion about adding new standard msg type to ROS. We use bags because of: timestamps for every video frame, possible to add information between frames and expand them at some point

Ok, clear.

Which messages are you using now to store data in the bag file?

That's the main problem here, we've saved our data as the CameraInfo messages (which I'm aware isn't correct), but when playing the .bag, there's a warning:

For type [sensor_msgs/CameraInfo] stored md5sum [12345678911234567892123456789312] has invalid message definition.

Ah, ok. Now things are starting to become clearer.

re: CameraInfo and md5sum invalid: yes, if you did not use the actual msg, then that would fail and lead to these kind of errors.

To properly store data in a .bag, you'll need to use a ROS message.

This can be a custom one that you define or a standard one.

Is your intent to share your .bags with other ROS users or would you want to use those bags with standard ROS tools?

I'm just trying to understand your challenge. When it comes to the information you're trying to store, would it be possible to use a standard sensor_msgs/Image along with a synchronised stamped custom message containing the relevant meta data?

Or are there more complex cases that could not be cleared represented using a pair of these message types?

would it be possible to use a standard sensor_msgs/Image along with a synchronised stamped custom message containing the relevant meta data?

I've suggested this earlier, but it may have been lost in the long string of comments.

I would say this is going to be the approach to use.

Sorry for misleading, I've made a small presentation abot the problem: https://drive.google.com/file/d/1BMG5UdLPoEzSPQMGagaQ-7007fTNxyCV/view?usp=sharing So, in our current state we're not able to use standard Img msg because of new sensor technology which takes frames in multiple expositions (HDR)

@latida: no need to apologise. We were just making sure we understood you correctly.

The slides helped.

I think I would again suggest to post to ROS Discourse, as I believe this is more a question of "how should support for multi-exposure images be added to ROS?".

It might be that other community members see a way to do that (in a single message) with the current set of messages, but at least we could have a discussion about that.

If you do post to ROS Discourse, please include:

• a link to your ROS Answers post (this one)
• your presentation

...

... - a description of your problem (ie: we want to store and process multi-exposure images with ROS messages, how should we do that?"

I will make sure to provide some additional context if you do post (to prevent ppl there saying: "please post on ROS Answers".

Thank you for your patience and your help, I've posted this as a new topic on ROS Discourse and now waiting for the moderator to approve.

No problem.

Some expectation management: don't be discouraged if it takes some time for people to respond to your post.

Everyone is busy, and it may take a few days.