Opencv Video Saving in Python

openCV video saving in python

Try this. It's working for me (Windows 10).

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()

How to save a video after changing its speed with opencv in your folder?

You can use the fps parameter of the cv2.VideoWriter() method. The fps can be calculated by simple diving your frameTime variable by 1000, as the cv2.waitKey() method takes in a number and uses it as a thousandth of a second.

Note that if the cap never closed during the while loop, the while cap.isOpened() won't be any better than while True, meaning by the time the last frame is read, an error would occur, causing the writer.release() method to never be called, thus making the resulting file unreadable.

Here is how I would do it:

import cv2

cap = cv2.VideoCapture('Pothole testing.mp4')
ret, frame = cap.read() # Get one ret and frame 
h, w, _ = frame.shape # Use frame to get width and height
frameTime = 100

fourcc = cv2.VideoWriter_fourcc(*"XVID") # XVID is the ID, can be changed to anything
fps = 1000 / frameTime # Calculate fps
writer = cv2.VideoWriter("Pothole testing 2.mp4", fourcc, fps, (w, h)) # Video writing device

while ret: # Use the ret to determin end of video
    writer.write(frame) # Write frame
    cv2.imshow("frame", frame)
    if cv2.waitKey(frameTime) & 0xFF == ord('q'):
        break
    ret, frame = cap.read()

writer.release()
cap.release()
cv2.destroyAllWindows()

If all you need is the resulting file and not the progress window, you can omit a few lines:

import cv2

cap = cv2.VideoCapture('Pothole testing.mp4')
ret, frame = cap.read()
h, w, _ = frame.shape
frameTime = 100

fourcc = cv2.VideoWriter_fourcc(*"XVID")
fps = 1000 / frameTime
writer = cv2.VideoWriter("Pothole testing 2.mp4", fourcc, fps, (w, h))

while ret:
    writer.write(frame)
    ret, frame = cap.read()

writer.release()
cap.release()

How can i save a frame in a live video using opencv in python?

You can use imwrite function from your opencv to extract the current frame.

You can also add time and convert it to string for naming purpose for the output file.

import time as t
LiveVideo = VideoStream(src=0).start()
        while True:
            frame = LiveVideo.read()
            timestr = t.strftime("%Y%m%d-%H%M%S")
            cv2.imwrite("frame%s.jpg" % timestr, frame )

How to save a video in Python OpenCV

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()

How to save specific parts of video into separate videos using opencv in python?

Here is how I would do it:

import cv2

file = "video.avi"
parts = [(15, 30), (50, 79)]

cap = cv2.VideoCapture(file)
ret, frame = cap.read()
h, w, _ = frame.shape

fourcc = cv2.VideoWriter_fourcc(*"XVID")
writers = [cv2.VideoWriter(f"part{start}-{end}.avi", fourcc, 20.0, (w, h)) for start, end in parts]

f = 0
while ret:
    f += 1
    for i, part in enumerate(parts):
        start, end = part
        if start <= f <= end:
            writers[i].write(frame)
    ret, frame = cap.read()

for writer in writers:
    writer.release()

cap.release()

Explanation:

1. Import the cv2 module, define the name of the video file and the parts of the file you want to save into different video files:

import cv2

file = "video.avi"
parts = [(15, 30), (50, 79)]

2. Define a video capture device to read frames from the video file and read from it once to get the shape of the frames of the video:

cap = cv2.VideoCapture(file)
ret, frame = cap.read()
h, w, _ = frame.shape

3. Define a fourcc (four-character code), and define a list of video writers; one for every video you want to generate:

fourcc = cv2.VideoWriter_fourcc(*"XVID")
writers = [cv2.VideoWriter(f"part{start}-{end}.avi", fourcc, 20.0, (w, h)) for start, end in parts]

4. Define a while loop, but before that, define a variable to keep track of which frame the while loop is at in the capture device:

f = 0
while ret:
    f += 1

5. Using a for loop inside the while loop, loop through the start and end frames of the parts, using the enumerate method to allow the program to access the index of the parts each iteration is at when needed. If the variable defined before the while loop is between (inclusive) the start and end of the part, write that frame to the corresponding video writer (using the index provided by the enumerate method):

    for i, (start, end) in enumerate(parts):
        if start <= f <= end:
            writers[i].write(frame)
    ret, frame = cap.read()

6. Finally, release all the video writers and the capture device:

for writer in writers:
    writer.release()

cap.release()

Can't save a video in opencv

The problem is that the video codec and the video container format do not match.

When executing your code, I am getting an error message (in the console windows):

OpenCV: FFMPEG: tag 0x3234504d/'MP42' is not supported with codec id 15 and format 'mp4 / MP4 (MPEG-4 Part 14)'

[mp4 @ 00000155e95dcec0] Could not find tag for codec msmpeg4v2 in stream #0, codec not currently supported in container

• You are using fourcc = cv2.VideoWriter_fourcc(*'MP42'), and M420 applies video codec MPEG-4v2.
• Video output file name is 'output.mp4'.
  
  The .mp4 extension applies MP4 container format.

Apparently .mp4 video file cannot contain video encoded with MPEG-4v2 codec.

You may either change codec, or change file format.

Example:

• Changing output file name to 'output.avi' or 'output.wmv' works.
• Changing the codec to MPEG-4: fourcc = cv2.VideoWriter_fourcc(*'mp4v') (and keeping file name 'output.mp4') also works.

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One more issue:

Add the following code after ret, frame = cap.read():

if not ret:
    break;

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