Writing an mp4 video using python opencv

Question

I want to capture video from a webcam and save it to an mp4 file using opencv. I found example code on stackoverflow (below) that works great. The only hitch is that I\'m trying

Answer 1

fourcc = cv2.VideoWriter_fourcc(*'mp4v')

'mp4v' returns no errors unlike 'MP4V' which is defined inside fourcc

for the error "OpenCV: FFMPEG: tag 0x5634504d/'MP4V' is not supported with codec id 13 and format 'mp4 / MP4 (MPEG-4 Part 14)' OpenCV: FFMPEG: fallback to use tag 0x00000020/' ???'"

Answer 2

For someone whoe still struggle with the problem. According this article I used this sample and it works for me:

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'X264')
out = cv2.VideoWriter('output.mp4',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()

So I had to use cv2.VideoWriter_fourcc(*'X264') codec. Tested with OpenCV 3.4.3 compiled from sources.

Answer 3

The problem such as OpenCV: FFMPEG: tag 0x5634504d/'MP4V' is not supported with codec id 13 and format 'mp4 / MP4 (MPEG-4 Part 14)' OpenCV: FFMPEG: fallback to use tag 0x00000020/' ???' maybe that your output video size is not the same as original video. You can look over the frame size of video first.

Answer 4

Anyone who's looking for most convenient and robust way of writing MP4 files with OpenCV or FFmpeg, can see my state-of-the-art VidGear Video-Processing Python library's WriteGear API that works with both OpenCV backend and FFmpeg backend and even supports GPU encoders. Here's an example to encode with H264 encoder in WriteGear with FFmpeg backend:

# import required libraries
from vidgear.gears import WriteGear
import cv2

# define suitable (Codec,CRF,preset) FFmpeg parameters for writer
output_params = {"-vcodec":"libx264", "-crf": 0, "-preset": "fast"}

# Open suitable video stream, such as webcam on first index(i.e. 0)
stream = cv2.VideoCapture(0) 

# Define writer with defined parameters and suitable output filename for e.g. `Output.mp4`
writer = WriteGear(output_filename = 'Output.mp4', logging = True, **output_params)

# loop over
while True:

    # read frames from stream
    (grabbed, frame) = stream.read()

    # check for frame if not grabbed
    if not grabbed:
      break

    # {do something with the frame here}
    # lets convert frame to gray for this example
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    # write gray frame to writer
    writer.write(gray)

    # Show output window
    cv2.imshow("Output Gray Frame", gray)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.release()

# safely close writer
writer.close() 

• Source: https://github.com/abhiTronix/vidgear
• Docs: https://abhitronix.github.io/vidgear/
• More FFmpeg backend examples:https://abhitronix.github.io/vidgear/gears/writegear/compression/usage/
• OpenCV backend examples: https://abhitronix.github.io/vidgear/gears/writegear/non_compression/usage/