Writing an mp4 video using python opencv

This worked for me.

self._name = name + '.mp4'
self._cap = VideoCapture(0)
self._fourcc = VideoWriter_fourcc(*'MP4V')
self._out = VideoWriter(self._name, self._fourcc, 20.0, (640,480))

What worked for me was to make sure the input 'frame' size is equal to output video's size (in this case, (680, 480) ).

http://answers.opencv.org/question/27902/how-to-record-video-using-opencv-and-python/

Here is my working code (Mac OSX Sierra 10.12.6):

cap = cv2.VideoCapture(0)
cap.set(3,640)
cap.set(4,480)

fourcc = cv2.VideoWriter_fourcc(*'MP4V')
out = cv2.VideoWriter('output.mp4', fourcc, 20.0, (640,480))

while(True):
    ret, frame = cap.read()
    out.write(frame)
    cv2.imshow('frame', frame)
    c = cv2.waitKey(1)
    if c & 0xFF == ord('q'):
        break

cap.release()
out.release()
cv2.destroyAllWindows()

Note: I installed openh264 as suggested by @10SecTom but I'm not sure if that was relevant to the problem.

Just in case:

brew install openh264

There are some things to change in your code:

1. Change the name of your output to 'output.mp4' (change to .mp4)
2. I had the the same issues that people have in the comments, so I changed the fourcc to 0x7634706d: out = cv2.VideoWriter('output.mp4',0x7634706d , 20.0, (640,480))

This is the default code given to save a video captured by camera

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()

For about two minutes of a clip captured that FULL HD

Using

cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)
cap.set(3,1920)
cap.set(4,1080)
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (1920,1080))

The file saved was more than 150MB

Then had to use ffmpeg to reduce the size of the file saved, between 30MB to 60MB based on the quality of the video that is required changed using crf lower the crf better the quality of the video and larger the file size generated. You can also change the format avi,mp4,mkv,etc

Then i found ffmpeg-python

Here a code to save numpy array of each frame as video using ffmpeg-python

import numpy as np
import cv2
import ffmpeg

def save_video(cap,saving_file_name,fps=33.0):

    while cap.isOpened():
        ret, frame = cap.read()
        if ret:
            i_width,i_height = frame.shape[1],frame.shape[0]
            break

    process = (
    ffmpeg
        .input('pipe:',format='rawvideo', pix_fmt='rgb24',s='{}x{}'.format(i_width,i_height))
        .output(saved_video_file_name,pix_fmt='yuv420p',vcodec='libx264',r=fps,crf=37)
        .overwrite_output()
        .run_async(pipe_stdin=True)
    )

    return process

if __name__=='__main__':

    cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)
    cap.set(3,1920)
    cap.set(4,1080)
    saved_video_file_name = 'output.avi'
    process = save_video(cap,saved_video_file_name)

    while(cap.isOpened()):
        ret, frame = cap.read()
        if ret==True:
            frame = cv2.flip(frame,0)
            process.stdin.write(
                cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
                    .astype(np.uint8)
                    .tobytes()
                    )

            cv2.imshow('frame',frame)
            if cv2.waitKey(1) & 0xFF == ord('q'):
                process.stdin.close()
                process.wait()
                cap.release()
                cv2.destroyAllWindows()
                break
        else:
            process.stdin.close()
            process.wait()
            cap.release()
            cv2.destroyAllWindows()
            break

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/' ???'"

This worked for me, I added images.sort() to keep the sequence order:

import cv2
import numpy as np
import os

image_folder = 'data-set-race-01'
video_file = 'race-01.mp4'
image_size = (160, 120)
fps = 24

images = [img for img in os.listdir(image_folder) if img.endswith(".jpg")]
images.sort()

out = cv2.VideoWriter(video_file, cv2.VideoWriter_fourcc(*'MP4V'), fps, image_size)

img_array = []
for filename in images:
    img = cv2.imread(os.path.join(image_folder, filename))
    img_array.append(img)
    out.write(img)

out.release()

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.

You need to set the codec to 'mp4v' (lowercase). If set in uppercase, an error would be thrown saying that is not supported, suggesting to use lowercase instead: OpenCV:FFMPEG:fallback to use tag 0x7634706d/'mp4v'. You may also want to have a look at the documentation of VideoWriter, as well as the examples given here. Also, please make sure your output video's size is equal to your input frame size (the below takes care of this, using the dimensions of the VideoCapture object).

cap = cv2.VideoCapture(0)
w = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
h = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
fps = cap.get(cv2.CAP_PROP_FPS) 
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
out = cv2.VideoWriter('output.mp4', fourcc, fps, (int(w),int(h)))

You can get the entire list of codecs available for mp4, etc., by setting fourcc=-1. For instance:

out = cv2.VideoWriter('output.mp4', -1, fps, (int(w),int(h)))

The OpenCV documentation is not very rich with regard to the VideoWriter, however I managed to get it working in the following way (by looking at the stacktrace):

import cv2

HEIGHT = 480
WIDTH = 640
FPS = 30.0

cap = cv2.VideoCapture(0, cv2.CAP_ANY)

cap.set(cv2.CAP_PROP_FPS, FPS)
cap.set(cv2.CAP_PROP_CONVERT_RGB , 1)
cap.set(cv2.CAP_PROP_BUFFERSIZE, 100)


cap.set(cv2.CAP_PROP_FRAME_WIDTH, WIDTH)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, HEIGHT)

fourcc = cv2.VideoWriter_fourcc(*'mp4v')

# output parameters such as fps and size can be changed
output = cv2.VideoWriter("output.mp4", fourcc, FPS, (WIDTH, HEIGHT))

while True:
    if cap.isOpened():
        (ret, frame) = cap.read()
        if ret:
            output.write(frame)
        cv2.imshow("frame", frame)

    if cv2.waitKey(10) == ord('q'):
        break

output.release()
cap.release()
cv2.destroyAllWindows()

The stacktrace error was:

OpenCV: FFMPEG: tag 0x5634504d/'MP4V' is not supported with codec id 12 and 
format 'mp4 / MP4 (MPEG-4 Part 14)'
OpenCV: FFMPEG: fallback to use tag 0x7634706d/'mp4v'

Unfortunately, it is difficult to find a list of the official codecs used by OpenCV, or at least I could not find them. In any case, it appears that you have to enter the codec 'mp4v' written in lower case.

https://docs.opencv.org/3.4/dd/d01/group__videoio__c.html#gac005718f121379beffdbdbfb44f2646a

One important thing I noticed is that the aspect ratio of the frame and the output video must be the same, which is why I use two variables for height and width. If these two are different, the file is created, but the frames are not saved (you always end up with a 1KB mp4 file). To avoid any problems you could do the same for FPS.

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.

On Ubuntu 22.04 (2023) cv2.VideoWriter_fourcc(*'mp4v') worked for me.

This works for me,

OS: Windows 11

Python: 3.12.0

OpenCV: 4.9.0.80

import cv2

vid_source_path = 0     # Path to video source, 0 for webcam
# vid_source_path = 'input_vi.mp4'     # Path to video source, 0 for webcam
cap = cv2.VideoCapture(vid_source_path)

if not cap.isOpened():
    print("Error: Could not open video Source.")
    exit()


# Define the codec and create VideoWriter object
ret = False
while not ret:
    ret, frame = cap.read()
    if not ret:
        print("Failed to grab the first frame from the video source, Trying again...")
    else:
        print(f'Height: {frame.shape[0]}, Width: {frame.shape[1]}')

height, width = frame.shape[:2]

# TO save the video in AVI format
# fourcc = cv2.VideoWriter_fourcc(*'XVID')  # You can change the codec if needed
# out = cv2.VideoWriter('output_vid.avi', fourcc, 20.0, (width, height))


# To save the video in MP4 format
# Note: 'X264' might not work on some systems, 'MP4V' or 'AVC1' can be alternatives.
fourcc = cv2.VideoWriter_fourcc(*'X264')
out = cv2.VideoWriter('output_vid.mp4', fourcc, 20.0, (width, height))



while (cap.isOpened()):
    ret, frame = cap.read()
    if ret != True:
        break

    # write the frame
    out.write(frame)

    cv2.imshow('frame',frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break


cap.release()
out.release()
cv2.destroyAllWindows()

just change the codec to "DIVX". This codec works with all formats.

fourcc = cv2.VideoWriter_fourcc(*'DIVX')

i hope this works for you!