Does the zed camera always save a picture instead of a video when it opens the video and writes the video file?

Software
1

When I use the following program to open the camera and read the program, the video stream cannot be saved, and the object saved is a picture. May I ask what the problem is, thank you

import cv2
import pyzed.sl as sl

zed = sl.Camera()
init_params = sl.InitParameters()
init_params.depth_mode = sl.DEPTH_MODE.PERFORMANCE
init_params.coordinate_units = sl.UNIT.METER
init_params.camera_resolution = sl.RESOLUTION.HD720
init_params.camera_fps = 30

# open camera
err = zed.open(init_params)
if err != sl.ERROR_CODE.SUCCESS:
    exit(1)

image = sl.Mat()

while True:
    zed.grab()
    zed.retrieve_image(image, sl.VIEW.LEFT)
    view = image.get_data()  # 从mat 转换成numpy数组了
    img0 = view[:, :, 0:3]
    cv2.imshow("hello", img0)
    cv2.waitKey(1)
    fps, w, h = 10, img0.shape[1], img0.shape[0]
    vid_writer = cv2.VideoWriter('outpy.mp4', cv2.VideoWriter_fourcc(*'mp4v'), fps, (w, h))
    vid_writer.write(img0)

vid_writer.release()
cv2.destroyAllWindows()
2

Hi @zhangYQHBAU

I think you’re creating your video writer at each iteration of the loop. :wink:
Get the constructor out and just use vid_writer.write(img0).
Please let me know if it fixed it!

3

After the two structures are pulled out according to what you said, it is still not possible to save the video, and the result of saving is a picture

vid_writer = cv2.VideoWriter('outpy.mp4', cv2.VideoWriter_fourcc(*'mp4v'), fps, (w, h))
vid_writer.write(img0)
4

@zhangYQHBAU

The constructor is just the first of these two lines, the other (the method to write) should remain in the loop.
Something like this:

[...]

image = sl.Mat()
vid_writer = cv2.VideoWriter('outpy.mp4', cv2.VideoWriter_fourcc(*'mp4v'), fps, (w, h))

while True:
    zed.grab()
    zed.retrieve_image(image, sl.VIEW.LEFT)
    view = image.get_data()  # 从mat 转换成numpy数组了
    img0 = view[:, :, 0:3]
    cv2.imshow("hello", img0)
    cv2.waitKey(1)
    fps, w, h = 10, img0.shape[1], img0.shape[0]
    vid_writer.write(img0)

[...]
5

I have done just like you said， But it didn’t work

6

Hey @zhangYQHBAU

Did you get any error messages?
I managed to run your code with a few modifications.
I think what was happening is that you could not end the loop properly with the while True:, so you should either use a frame counter instead of looping forever, or use a key to finish the capture like this.

So:

  1. Initialize cv2.VideoWriter : vid_writer = cv2.VideoWriter('outpy.mp4', cv2.VideoWriter_fourcc(*'mp4v'), fps, (w, h))
  2. Either:
    a. loop with a counter : while frame_counter < desired_frames :
    b. loop with while True:, but at the end of the loop (inside the loop), listen to a key from the cv2 window to quit cleanly (q in this example).
    if k == ord('q'):
        break

Then you will arrive at vid_writer.release() properly and you should have a video.

If it still doesn’t work, please include error messages.