fixes rosbag storage_id and EventCDConverter import

[JackPieCZ]

Changes

1. Since the recommended tool to create bag files from raw files (event_camera_tools) generate mcap files by default, storage_id in read_bag_ros2.py file was changed from sqlite3 to mcap to avoid the following error when running src/mv_vs_frequency_cam.py file with defined --bag:

[ERROR] [1717085906.299389849] [rosbag2_storage]: Could not open '/mnt/d/_FEL/CMP/event_cam_experiments/event_cam_experiments/experiments/02_drill_slow_longer/drill_slow_bag/drill_slow_bag_0.mcap' with 'sqlite3'. Error: Failed to setup storage. Error: Error when processing SQL statement. SQLite error (26): fi
le is not a database
[ERROR] [1717085906.299537250] [rosbag2_storage]: Could not load/open plugin with storage id 'sqlite3'
Traceback (most recent call last):
  File "/mnt/d/_FEL/CMP/event_cam_experiments/event_cam_experiments/frequency_cam/src/mv_vs_frequency_cam.py", line 264, in <module>
    events, res, offset, _, _ = read_bag(
  File "/mnt/d/_FEL/CMP/event_cam_experiments/event_cam_experiments/frequency_cam/src/read_bag_ros2.py", line 117, in read_bag
    bag = BagReader(bag_path, topic)
  File "/mnt/d/_FEL/CMP/event_cam_experiments/event_cam_experiments/frequency_cam/src/read_bag_ros2.py", line 39, in __init__
    self.reader.open(storage_options, converter_options)
RuntimeError: No storage could be initialized. Abort

2. EventCDConverter is not defined in frequency_cam.py file as used on line 304 in file src/mv_vs_frequency_cam.py. To mitigate this error, EventCDConverter is imported from read_bag_ros2 as it was before the last commit.

Additional help required

After these two mentioned fixed, the mv_vs_frequency_cam.py starts without any errors or warnings. However, it produces a Seg fault at line 343 in file mv_vs_frequency_cam.py: mv_algo.process_events(evs). With this line commented out, the seg fault does not occur. Here is the full console output:

DESKTOP:~$/usr/bin/python3 ./src/mv_vs_frequency_cam.py --bag ./bag/
took 0.326548s to process 118, rate: 361.35538384819984 msgs/s, 6.73576234961081 Mev/s
Segmentation fault

[berndpfrommer]

Please email me your raw file (or link to cloud storage) so I can have a look at it.

[JackPieCZ]

Here is the data I used link
I know the mv_vs_frequency_cam.py was more for testing purposes than general use, but I thought you might want to know about this issue.

[berndpfrommer]

The way events are stored is now completely different from how it was way back when I wrote this experimental python code.
I created a new branch ("resurrect_python_code") which has some fixes for bag reading ("run_frequency_cam.py"). At least it reads the events now and feeds them into frequency cam. But much else is still broken.

[JackPieCZ]

Great! Thank you very much!

[berndpfrommer]

I fixed the worst of brokenness and added a README with PR #11.
The code quality is low and there are now tests. I tried it on the drill dataset you sent and it seemed to work.