I am trying to create a video from the python wrapper for OpenCV under OSX. I am using python 2.7.1, opencv 2.3.1a, and the python wrappers from willowgarage that come with that version of opencv. I have:
import cv,cv2 w = cv2.VideoWriter('foo.avi', cv.FOURCC('M','J','P','G'), 25, (100,100)) for i in range(100): w.write(np.ones((100,100,3), np.uint8))
WARNING: Could not create empty movie file container. Didn't successfully update movie file. ... [ 100 repetitions]
I'm not sure what to try next
There are many outdated and incorrect online guides on this topic-- I think I tried almost every one. After looking at the source QTKit-based implementation of VideoWriter on Mac OSX, I was finally able to get VideoWriter to output valid video files using the following code:
fps = 15 capSize = (1028,720) # this is the size of my source video fourcc = cv2.cv.CV_FOURCC('m', 'p', '4', 'v') # note the lower case self.vout = cv2.VideoWriter() success = self.vout.open('output.mov',fourcc,fps,capSize,True)
To write an image frame (note that the imgFrame must be the same size as capSize above or updates will fail):
When done be sure to:
vout.release() self.vout = None
This works for me on Mac OS X 10.8.5 (Mountain Lion): No guarantees about other platforms. I hope this snippet saves someone else hours of experimentation!
I am on macOS High Sierra 10.13.4, Python 3.6.5, OpenCV 3.4.1.
The below code (source: https://www.learnopencv.com/read-write-and-display-a-video-using-opencv-cpp-python/) opens the camera, closes the window successfully upon pressing 'q', and saves the video in .avi format.
Note that you need to run this as a .py file. If you run it in Jupyter Notebook, the window hangs when closing and you need to force quit Python to close the window.
import cv2 import numpy as np # Create a VideoCapture object cap = cv2.VideoCapture(0) # Check if camera opened successfully if (cap.isOpened() == False): print("Unable to read camera feed") # Default resolutions of the frame are obtained.The default resolutions are system dependent. # We convert the resolutions from float to integer. frame_width = int(cap.get(3)) frame_height = int(cap.get(4)) # Define the codec and create VideoWriter object.The output is stored in 'outpy.avi' file. out = cv2.VideoWriter('outpy.avi',cv2.VideoWriter_fourcc('M','J','P','G'), 10, (frame_width,frame_height)) while(True): ret, frame = cap.read() if ret == True: # Write the frame into the file 'output.avi' out.write(frame) # Display the resulting frame cv2.imshow('frame',frame) # Press Q on keyboard to stop recording if cv2.waitKey(1) & 0xFF == ord('q'): break # Break the loop else: break # When everything done, release the video capture and video write objects cap.release() out.release() # Closes all the frames cv2.destroyAllWindows()