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

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))

Answer 2

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

Answer 3

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()

Answer 4

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

Answer 5

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

fourcc = cv2.VideoWriter_fourcc(*'DIVX')

i hope this works for you!

Answer 6

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))