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I have bag file in ros2 rosbag2_2023_06_21-22_18_10_0.db3 which record the topic /image_raw/compressed I can visualize the image by ros2 run rqt_image_view rqt_image_view. now i want to convert back the bag file to .mp4 how can i do that?
I had a similar issue a week or two ago. Unfortunately I don't believe there's a neat solution as a bag is a container for one or multiple topics.
The solution I landed on was to make a simple python node to record video from (a) topic(s) of interest, then using cv_bridge and OpenCV's VideoWriter write that into the output file while playing back the bag.
Make sure you remember to have a destroy_node function that will release the VideoWriter before you call rclpy.shutdown() to avoid having the video not written correctly.
I don't have it on me unfortunately. https://stackoverflow.com/questions/7... is similar and may be a good reference point?
I write a python script that subscribe to /image_raw/compressed and save the video as output_video.mp4. here is the script
``` import rclpy from rclpy.node import Node from sensor_msgs.msg import CompressedImage import cv_bridge import cv2 import numpy as np
class ImageToVideoConverter(Node): def __init__(self): super().__init__('image_to_video_converter') self.bridge = cv_bridge.CvBridge() self.subscription = self.create_subscription( CompressedImage, '/image_raw/compressed', self.image_callback, 10 ) self.video_writer = None
def image_callback(self, msg):
try:
np_arr = np.frombuffer(msg.data, np.uint8)
cv_image = cv2.imdecode(np_arr, cv2.IMREAD_COLOR)
if self.video_writer is None:
self.init_video_writer(cv_image)
self.video_writer.write(cv_image)
except Exception as e:
self.get_logger().error('Error processing image: %s' % str(e))
def init_video_writer(self, image):
try:
height, width, _ = image.shape
video_format = 'mp4' # or any other video format supported by OpenCV
video_filename = 'output_video.' + video_format
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
fps = 30 # Frames per second
self.video_writer = cv2.VideoWriter(video_filename, fourcc, fps, (width, height))
except Exception as e:
self.get_logger().error('Error initializing video writer: %s' % str(e))
def destroy_node(self):
if self.video_writer is not None:
self.video_writer.release()
super().destroy_node()
def main(args=None): rclpy.init(args=args) image_to_video_converter = ImageToVideoConverter() rclpy.spin(image_to_video_converter) image_to_video_converter.destroy_node() rclpy.shutdown()
if __name__ == '__main__': main()
```
Asked: 2023-06-22 02:08:58 -0500
Seen: 1,419 times
Last updated: Jun 23 '23
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