Why does the following code not save the video?
Also is it mandatory that the frame rate of the webcam matches exactly with the VideoWriter frame size?
import numpy as np
import cv2
import time
def videoaufzeichnung(video_wdth, video_hight, video_fps, seconds):
cap = cv2.VideoCapture(6)
cap.set(3, video_wdth) # wdth
cap.set(4, video_hight) #hight
cap.set(5, video_fps) #hight
# Define the codec and create VideoWriter object
fps = cap.get(5)
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi', fourcc, video_fps, (video_wdth, video_hight))
#out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640, 480))
start = time.time()
zeitdauer = 0
while(zeitdauer < seconds):
end = time.time()
zeitdauer = end - start
ret, frame = cap.read()
if ret == True:
frame = cv2.flip(frame, 180)
# write the flipped frame
out.write(frame)
cv2.imshow('frame', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
videoaufzeichnung.videoaufzeichnung(1024, 720, 10, 30)
I suspect you're using the libv4l version of OpenCV for video I/O. There's a bug in OpenCV's libv4l API that prevents VideoCapture::set method from changing the video resolution. See links 1, 2 and 3. If you do the following:
...
frame = cv2.flip(frame,180)
print(frame.shape[:2] # check to see frame size
out.write(frame)
...
You'll notice that the frame size has not been modified to match the resolution provided in the function arguments. One way to overcome this limitation is to manually resize the frame to match resolution arguments.
...
frame = cv2.flip(frame,180)
frame = cv2.resize(frame,(video_wdth,video_hight)) # manually resize frame
print(frame.shape[:2] # check to see frame size
out.write(frame)
...
output-frame & input-frame sizes must be same for writing...
Related
I am applying Canny edge detector in a video using OpenCV. I can see the result in a window and then I am writing the video. Even though I can see the right result on the window, the result in the output file is not the same.
Here is the code and what I can see in the window and in the output file. Any idea what can cause this?
I am not sure what is the output of Canny and if I have to turn it to type of data that will fit with the rest of the video.
`
import cv2
import numpy as np
cap = cv2.VideoCapture('New_video.mp4')
if (cap.isOpened() == False):
print("Unable to read camera feed")
frame_width = int(cap.get(3))
frame_height = int(cap.get(4))
fps = int(round(cap.get(5)))
out = cv2.VideoWriter('output.mp4', cv2.VideoWriter_fourcc(*'mp4v'), fps,
(frame_width, frame_height))
while (True):
ret, frame = cap.read()
if ret == False:
break
if between (cap,40000,45000):
gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
frame = cv2.blur(gray,(5,5))
frame = cv2.Canny(frame,20,60)
if between (cap,45000,50000):
gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
frame = cv2.blur(gray,(5,5))
frame = cv2.Canny(frame,150,250)`
out.write(frame)
cv2.imshow('frame',frame)
Try using XVID fourcc codec instead of mp4v. Also,VideoWriter method has one more parameter isColor which is set to be true by default. It should be set to False whenever we use gray scale images.
https://docs.opencv.org/3.4/dd/d9e/classcv_1_1VideoWriter.html
This is my code to save web_cam streaming. It is working but the problem with output video file.
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
#fourcc = cv2.cv.CV_FOURCC(*'DIVX')
#out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
out = cv2.VideoWriter('output.avi', -1, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
Here's some simple code to save frames into a video file. I recommend creating another thread for obtaining the frames since cv2.VideoCapture.read() is blocking. This can be expensive and cause latency as the main thread has to wait until it has obtained a frame. By putting this operation into a separate thread that just focuses on grabbing frames and processing/saving the frames in the main thread, it dramatically improves performance due to I/O latency reduction. You also can experiment with other codecs but using MJPG should be safe since its built into OpenCV.
from threading import Thread
import cv2
class WebcamVideoWriter(object):
def __init__(self, src=0):
# Create a VideoCapture object
self.capture = cv2.VideoCapture(src)
# Default resolutions of the frame are obtained (system dependent)
self.frame_width = int(self.capture.get(3))
self.frame_height = int(self.capture.get(4))
# Set up codec and output video settings
self.codec = cv2.VideoWriter_fourcc('M','J','P','G')
self.output_video = cv2.VideoWriter('output.avi', self.codec, 30, (self.frame_width, self.frame_height))
# Start the thread to read frames from the video stream
self.thread = Thread(target=self.update, args=())
self.thread.daemon = True
self.thread.start()
def update(self):
# Read the next frame from the stream in a different thread
while True:
if self.capture.isOpened():
(self.status, self.frame) = self.capture.read()
def show_frame(self):
# Display frames in main program
if self.status:
cv2.imshow('frame', self.frame)
# Press Q on keyboard to stop recording
key = cv2.waitKey(1)
if key == ord('q'):
self.capture.release()
self.output_video.release()
cv2.destroyAllWindows()
exit(1)
def save_frame(self):
# Save obtained frame into video output file
self.output_video.write(self.frame)
if __name__ == '__main__':
webcam_videowriter = WebcamVideoWriter()
while True:
try:
webcam_videowriter.show_frame()
webcam_videowriter.save_frame()
except AttributeError:
pass
The output file is corrupted because of the wrong frame rate and frame resolution. Using this code :
out = cv2.VideoWriter('output.avi', -1, 20.0, (640,480))
We set the fps/frame rate per second 20. Which was not correct. Also, the frame width and height was wrong. I solved by getting fps, width, height from the captured web_cam profile.
cap = cv2.VideoCapture(0) #web-cam capture
fps = cap.get(cv2.CAP_PROP_FPS)
width = cap.get(cv2.CAP_PROP_FRAME_WIDTH) # float
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT) # float
out = cv2.VideoWriter('output.avi', -1,fps, (int(width), int(height)))
I added codec parameter to function cv2.videowriter.
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
#fourcc = cv2.cv.CV_FOURCC(*'DIVX')
#out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
fps = cap.get(cv2.CAP_PROP_FPS)
width = cap.get(cv2.CAP_PROP_FRAME_WIDTH) # float
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
codec = cv2.VideoWriter_fourcc('M', 'J', 'P', 'G')
out = cv2.VideoWriter('output.avi',codec,fps, (int(width),\
int (height)))
#out = cv2.VideoWriter('output.avi', -1, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q') :
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
I hope you may see what is different in my code and your code.
Mine works now. Using MJPG codec for .avi extention
the indention is a bit messed,please do forgive cause I am very first time user.
The video file is no longer corrupt.
I got the info from: Link
I have opened a Video using CV2, made some changes using cv2.rectangle.
Now, when I do cv2.imshow('frame',frame), it plays the video.
Instead of this, I want to save the video somewhere, in the original size and frame rate.
You can save video frame by frame. Based on example on docs:
Open Cv video capture
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
I capture video from my camera, but when i save this i received very fast video. Can i capture video with original frame rate?
import cv2
import time
# exit(1)
cap = cv2.VideoCapture("rtsp://192.168.0.66/live1.sdp")
ps = cap.get(cv2.CAP_PROP_FPS)
width = cap.get(cv2.CAP_PROP_FRAME_WIDTH) # float
# Get current height of frame
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT) # float
fourcc = cv2.VideoWriter_fourcc(*'XVID')
FILE_OUTPUT = 'out.avi'
FPS = 20.0
cap.set(cv2.CAP_PROP_FPS, FPS)
out = cv2.VideoWriter(FILE_OUTPUT, fourcc, FPS, (int(width), int(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)
# cv2.waitKey(100)
# 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()
P.S i use opencv 4 and python3. I try change waitKey option but it had no effect
I cant figure out why this is not working.
The following code works perfectly using my webcam:
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
Yet when I exchange the Webcam for a video file, the output does not generate a video. Only a 5.7kb file named output.avi:
import numpy as np
import cv2
cap = cv2.VideoCapture('Input.avi')
# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
I can see in my windows that the video is being processed but is not being saved. I have also tried changing the resolution to match the initial video file.
I'm using OpenCV on Ubuntu, and this worked for me:
out = cv2.VideoWriter("output.avi", cv.CV_FOURCC(*'DIVX'), fps, (640, 480))
See if it works on Windows.