Converting numpy array to video

I’m using OpenCV for processing a video, saving the processed video

Example:

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()

Source file is FULL HD 2 minutes clip in avi format with Data Rate 7468kbps Saved file is FULL HD 2 minutes clip in avi format with Data Rate 99532kbps

this is confusing if i save each frame and give it to input, I get an error in the .output saving there is no such file

import ffmeg
(
    ffmpeg
    .input('/path/to/jpegs/*.jpg', pattern_type='glob', framerate=25)
    .output('movie.mp4')
    .run()
)

How do i save the video as the same size as the source using ffmeg-python?

[kylemcdonald]

not sure if this is what you were asking, but here is some code to save frames from memory straight to a video file. if you chop this up a little you could hack it into your initial code and avoid writing the jpgs to disk:

def vidwrite(fn, images, framerate=60, vcodec='libx264'):
    if not isinstance(images, np.ndarray):
        images = np.asarray(images)
    n,height,width,channels = images.shape
    process = (
        ffmpeg
            .input('pipe:', format='rawvideo', pix_fmt='rgb24', s='{}x{}'.format(width, height))
            .output(fn, pix_fmt='yuv420p', vcodec=vcodec, r=framerate)
            .overwrite_output()
            .run_async(pipe_stdin=True)
    )
    for frame in images:
        process.stdin.write(
            frame
                .astype(np.uint8)
                .tobytes()
        )
    process.stdin.close()
    process.wait()

Edit 2020-01-28: My working version of this function is backed by a small class, implemented in my python-utils/ffmpeg.py

[CharlesSS07]

@jaehobang Were you able to figure out this problem? Because I am having the same problem with a [Errno 32] Broken pipe error.

[Error 32] Broken Pipe means the process errored and closed so there was no pipe to pipe input into. You can figure out what the error was by looking in process.stderr, like so:

import ffmpeg
import io


def vidwrite(fn, images, framerate=60, vcodec='libx264'):
    if not isinstance(images, np.ndarray):
        images = np.asarray(images)
    _,height,width,channels = images.shape
    process = (
        ffmpeg
            .input('pipe:', format='rawvideo', pix_fmt='rgb24', s='{}x{}'.format(width, height), r=framerate)
            .output(fn, pix_fmt='yuv420p', vcodec=vcodec, r=framerate)
            .overwrite_output()
            .run_async(pipe_stdin=True, overwrite_output=True, pipe_stderr=True)
    )
    for frame in images:
        try:
            process.stdin.write(
                frame.astype(np.uint8).tobytes()
            )
        except Exception as e: # should probably be an exception related to process.stdin.write
            for line in io.TextIOWrapper(process.stderr, encoding="utf-8"): # I didn't know how to get the stderr from the process, but this worked for me
                print(line) # <-- print all the lines in the processes stderr after it has errored
            process.stdin.close()
            process.wait()
            return # cant run anymore so end the for loop and the function execution

In my case , it was just

Unknown encoder 'libx264'

because I hadnt’t installed that library