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I used the following page from
OpenCV 3.0.0
tutorial:
Tutorial in docs
When I tried to use the example that saves videos, it doesn't work.
It displays the content from the webcam, and also creates a file called
output.avi
, but when I checked the size of
ouput.avi
, it was zero bytes.
I also tried using different codecs, like
YUY2
.
I use
Python 2.7.8
and
OpenCV 3.0.0
and
Windows 8.1
–
I had the same problem and I solved it by specifying the video output resolution to exactly the same as input:
cap = cv2.VideoCapture('vtest.avi')
out = cv2.VideoWriter('output.avi',fourcc, 20.0,(int(cap.get(3)),int(cap.get(4))))
Of course make sure you got ffmpeg installed and working.
I was struggling with this problem for a few hours then I realized that I had typed the image's shape wrong.
It is (width, height), ie:
(image.shape[1], image.shape[0])
and not
(image.shape[0], image.shape[1])
This is how my working code looks like finally... (I am on a Windows machine):
video_path = FILENAME + '.avi'
size = images[0].shape[1], images[0].shape[0] ## <<<--- NOTICE THIS
video = cv2.VideoWriter(video_path,cv2.VideoWriter_fourcc(*'DIVX'), 60, size)
for img in images:
video.write(img)
cv2.destroyAllWindows()
video.close()
More generally:
Look up the fourcc code of the video compression format you're after here, and whatever the code is - for instance 'FMP4' for FFMpeg - plug it in in the following manner:
cv2.VideoWriter_fourcc('F','M','P','4')
–
Make sure you are using the correct fourcc 4-byte code. The example on the tutorial has:
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
This XVID code may only work for linux. The documentation above the example states (in the tutorial):
"In Windows: DIVX (More to be tested and added)." So if you haven't, try replacing the fourcc line above with:
fourcc = cv2.VideoWriter_fourcc(*'DIVX')
I use cv2.VideoWriter on linux quite often and it always works. So if the above doesn't work you can always try it on a linux vm.
–
–
–
In my case, I thought the codec was an obstacle but it wasn't. Instead, adjusting the dimensions being consumed by videoWriter() did the trick:
(ok, frame) = cv2.VideoCapture(videoPath).read()
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter(output, fourcc, 10.0, (1280, 720))
(1280,720) was used because frame.shape from my video outputs (1280, 720, 3). It made avi to mp4 and vice versa possible. Didn't have to worry about reconciling the codec.
Check the resolution of your images!
I was trying with odd-shaped images (1284x709) and ended up with unreadable videos of 1k in size. After resizing my image to the closest 'common' resolution:
image = cv2.resize(image, (1280,720)),
it worked just fine.
–
I suspect there are a lot of reasons video writing fails silently, and in my case, my frame was a composite of a 3 channel image and a 4 channel image (transparent overlay). Converting the end result to BGR format as follows allowed the video to save successfully.
width = 1280
height = 720
FPS = 30
fourcc = VideoWriter_fourcc(*'avc1')
video = VideoWriter('output.mp4', fourcc, float(FPS), (width, height))
for img in images:
frame = cv2.cvtColor(img, cv2.COLOR_BGRA2BGR)
video.write(frame)
video.release()
On windows 7 and using Python 2.7 and OpenCV 2.4.8, I experienced the fact that if the file NAME is "output.mpg" would not write.
I solved it by changing to "output.avi".
I have the exact same issue. I am using OpenCV in C++, but I believe you can still pass -1 instead of choosing the codec so you can have a drop down menu of the available codecs even in python. From there I tried all different codecs and just like Leonard Zhou, the IYUV codec was the one that worked for me. Also note that it was the only one that worked even though I could use XVID just fine on another machine with the same code and same codec installer.
EDIT:
What I suggested worked as a patch, the main issue was solved on my end by adding the opencv_ffmpeg dll in the executable's folder.
I changed the Video writer size to my screen resolution size and it worked.
here is the solution.
out = cv2.VideoWriter("output.avi", fourcc, 5.0, (1920, 1080))
It worked for me after I assigned the actual frame size and not what I thought the size was:
ret, frame = cap.read()
height, width, channels = frame.shape
codec = cv2.VideoWriter_fourcc(*"DIVX")
out=cv2.VideoWriter('new.avi',codec ,20.0,(width, height))
And put out.write(frame) inside the while loop before cv2.imshow("Frame", frame).
–
After trying hours to find the error, I finally found it. So here are some things to keep in mind. (For Linux users particularly)
Use this codec ("MJPG").
cv2.VideoWriter_fourcc(*'MJPG')
Do not forget to write the Boolean value as final argument (True for RGB and False for GrayScale) in
cv2.VideoWriter(path, fourcc, float(frameRate), frameSize, True)
The argument, frameSize required by cv2.VideoWriter is a tuple of form (width, height) and not (height, width) which is the shape of image array if you open the image using cv2.read or Image.open. So don't forget to invert it.
To state the obvious, make sure you're giving not only a correct path, but also a video name.
i.e. path/'video.avi' and not just path/. It will fail silently otherwise.
I had same issue that the video file was being created without any errors but it won't run and had a size of few KBs. Here's how I resolved it;
Make sure you have passed FPS argument in float value.
The output resolution needs to be same as of input video resolution.
The above methods work only for RGB frames/images. Incase you are trying to write a grayscale image, pass a parameter 0 to the VideoWriter():
fourcc = cv2.VideoWriter_fourcc(*"MJPG")
out = cv2.VideoWriter('output.avi', fourcc, 30, size, 0)
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