Unable to successfully play rosbag containing topics of type realsense_msgs/Notification

[uhobeike]

Hello.
We are developing a robot with D435i.
I have been concerned for some time that the rosbag recorded using realsense-viewer may not play back properly.

Therefore, this Pull Request proposes a fix to resolve the issue and successfully play rosbag.
I would like to discuss whether this fix is appropriate, as it may affect other parts of the system that are not related to ros.

Environment I used

	Details
Camera	D435i（Connected via USB2.0）
OS	Ubuntu 18.04 LTS
ROS	Melodic
CPU	Intel® Core™ i7-8665U CPU @ 1.90GHz × 8

Commands used（When recording rosbag）

realsense-viewer 

Commands used（Playing back recorded rosbags causes errors）

roscore
rosbag play space_existence_topic_notification.bag

Error log

ikebe@ikebe:~$ rosbag play space_existence_topic_notification.bag 
[ INFO] [1659491276.715054503]: Opening space_existence_topic_notification.bag

[FATAL] [1659491276.779427919]: Character [ ] at element [38] is not valid in Graph Resource Name [/device_0/sensor_1/notification/Frames Timeout].  Valid characters are a-z, A-Z, 0-9, / and _.

Detailed explanation of this issue

ros does not consider names containing spaces.

Reference)

• http://wiki.ros.org/ja/Names
• ros/ros_comm/clients/roscpp/src/libros/names.cpp

Therefore, if you create a topic that contains spaces, it will fail when loaded.

However, topics of type realsense_msgs/Notification
All of them contain whitespace in the suffix.
I can solve this by using rosbag filter to remove the topic, but
However, we believe that it is difficult to parse realsense_msgs/Notification type topics without modification.

Therefore, we have proposed a modification to create topics without spaces.

Reproduction method

How to create a rosbag containing topics of type realsense_msgs/Notification

• Environment building
  Build and install librealsense2 SDK

git clone https://github.com/IntelRealSense/librealsense
./scripts/setup_udev_rules.sh
cd librealsense
mkdir build && cd build
cmake .. -DBUILD_EXAMPLES=true
make -j8
sudo make install
sudo ldconfig

• Launching realsense-viewer

realsense-viewer

• Rosbag records（To have a topic of type realsense_msgs/Notification created, intentionally connect the PC to the D435i via USB 2.0.）

create-realsense_msgs-Notification-topic-2022-08-03_11.25.56.mp4

Experiment

Error

• If you run the source in the master branch

play-space-existence-topic-notification-rosbag-2022-08-03_11.29.27.mp4

If modified

• If the source in the master branch reflects this modification
  In the modified source, rosbag can contain topics of type realsense_msgs/Notification that do not contain spaces.

play-space-no-existence-topic-notification-rosbag-2022-08-03_11.37.35.mp4

[Nir-Az]

@uhobeike thanks for the PR,
As I know the SDK use a customized version of the ROSBAG protocol.
I suggest to try playing the file using the RS ROS API.
Anyway, the development team is currently focused on ROS2 development and we will happily try to help if you see an issue on the ROS2 wrapper.