Unable to get sensor data from recorded file using world.get_actors()

[zl3466]

Hi all, I am currently trying to get existing sensors from a recorded .log file with the function world.get_actors(). However, it appears that the function only returns the landmarks (type = 'traffic.') and vehicles (type = 'vehicle.'), but not sensors (type = 'sensors.*'). Meanwhile, running show_recorder_file_info.py upon the .log file gives me proper records of creations of the sensors.

what I did in terms of coding is simply adding
world = client.get_world()
print(world.get_actors().filter('sensors.*'))
directly after the client.replay_file function call in the start_replaying.py file from the API example folder.

A similar problem has been raised here and claimed to be a bug, but the follow up comment says that the bug has been fixed. Yet I am still unable to retrieve sensors with world.get_actors() from recordings.

I am not sure if this matters, but the recording was generated with sync mode = True during the simulation, as I was visualizing multiple sensors (showing multiple camera and lidar views using cv2.imshow()) in the process. This thread says it should be fine as long as I am running the replay in the same map as I performed the simulation, which I did.

My ultimate goal is to reproduce the multi-sensor visualization from recording .log files, which requires the extraction of spawned sensors, to the data of which I can listen(), callback, process, and visualize.

here's the partial code from my modified start_replaying.py. the get_actors() action is at the very bottom.

try:

    client = carla.Client(args.host, args.port)
    client.set_timeout(60.0)

    # set the time factor for the replayer
    client.set_replayer_time_factor(args.time_factor)

    # set to ignore the hero vehicles or not
    client.set_replayer_ignore_hero(args.ignore_hero)

    # replay the session
    print(client.replay_file(args.recorder_filename, args.start, args.duration, args.camera, args.spawn_sensors))
    
    world = client.get_world()
    print(world.get_actors().filter('vehicle.*'))

finally:
    pass

Plzzz let me know if anyone has any idea how to properly extract sensor data from recording files. Thanks!!!

[Morphlng]

Hello! I'm wondering if you have solved this problem?

We are trying to collect data from a series of replay files. get_actor(id) will return the sensor I want, but the problem to me is that only "RGB" camera can register a callback and work, the CollisionSensor and LaneInvasionSensor in my case, doesn't call the callback function I registered through listen at all.

I find that the replay file itself record the event of collision, however there are no events for lane_invasion. I cannot get that data without a functioning callback. I have tried Carla 0.9.13 and Carla 0.9.14, both doesn't work.

[LarryYang1]

@Morphlng

Hello! I want to do the same thing as you did. I firstly make a record through a simulation with 6 cameras, then I want to replay the recording, and handle 6 cameras' input for each frames. Should I create new 6 cameras to register callbacks, or use the existing 6 cameras to register callbacks? I noticed during replay, there already have 6 cameras, but all their attributes data are wrong... Could you share some sample code to show how you make it work? Thanks in advance!

[Morphlng]

Hi @LarryYang1 ! I don't remember where I have seen this, but the mechanism of Carla's replay is "teleporting" the actors frame by frame, to simulate its "moving". So some of the data (e.g. vehicle.get_velocity()) and sensor data (e.g. LaneInvasion) is not able to retreive. If you only want RGB camera data, then I recommend you to setup some new sensor after you client.replay_file.

I don't have some ready-to-go scripts, but the script should be something like this:

1. client.load_world manually to which the record happened. (Recommended)
2. world.apply_settings to switch to synchronous_mode. (It is also recommended to record in sync mode with fixed delta seconds)
3. client.replay_file to load the record. (I once wrote a replay_parser for Carla, that can get all vehicle's id beforehand. This should work under Carla 0.9.13)
4. world.tick until all vehicles are spawned.
5. Setup sensors at this point.
6. Finish your data collection logic.

[LarryYang1]

@Morphlng, Thanks for your quick response, I can't get camera callback data with new sensors, but it seems I can get camera callback if I register those callbacks to existing camera sensors, after replay_file, then I can get sensor data from existing IMU, GNSS, camera, but just no callback data for speedometer. I noticed that the attributes for the existing cameras are wrong, anyway, I will check the input data from existing cameras and see whether they are as expected or not...