Performance limitations with rtabmap-kitti_dataset tool?

Posted by dave on
URL: http://official-rtab-map-forum.206.s1.nabble.com/Performance-limitations-with-rtabmap-kitti-dataset-tool-tp10730.html

Dear Mathieu,

I am trying to use rtabmap on my own dataset in an environment with very few features, and I want to compare different feature detectors and descriptors.

I took some rosbags in ROS 2 and I am able to run rtabmap on the stereo images from the rosbag. However, I noticed that the performance on my laptop is limited, so I reduced the rosbag playback speed to 0.2 to eliminate the performance issues (which consist of losing the odometry).

I also made a script that can extract all the images from the rosbag (I need them later for another project), and I found out about the rtabmap-kitti_dataset tool (I have my data in the same format as the KITTI dataset), which allows me to run rtabmap on these extracted images without using ROS 2 at all. I expected this would also eliminate the performance issues as it should be able to go through the image pairs one-by-one and take all the time it needs to process. However, it also loses the odometry at the same position as with the rosbag at full playback speed.

When it loses the odometry, I get the following message:

```
[ WARN] (2024-12-02 16:21:27.226) Features2d.cpp:898::generateKeypoints3D() A large number (511/1000) of stereo correspondences are rejected! Optical flow may have failed because images are not calibrated, the background is too far (no disparity between the images), maximum disparity may be too small (128.000000) or that exposure between left and right images is too different.
```

1) The images are calibrated and rectified.

2) The background might not always be visible as the robot I use has the camera attached at a downward angle of 30 degrees (since the features to look at are on the ground, not the landscape), and therefore, there might not be a background in the FoV of the camera. Could this be an issue?

3) I tried increasing the maximum disparity value to 256 and even 512, but it still has the same issue.

4) The exposure of the stereo images is the same (to my eyes, at least), so I cannot believe this would be a limiting factor.

Which leads me to my initial question: Are there performance limitations with the rtabmap-kitti_dataset tool? Is there anything that tries to keep up with real-time performance when running this tool compared to running rtabmap on the rosbag data?

I found the parameter Rtabmap/DetectionRate = "1". Is this doing what I think to be forcing the real-time behaviour? I tried setting it to 0.2, but it did not change anything. Does it need to be an integer? What if I set it to 0?

Am I overlooking anything?

With kind regards,
Dave