How can I address large memory usage by MoviePy?

Question

I am trying to make a video from a large number of images using MoviePy. The approach works fine for small numbers of images, but the process is killed for large numbers of images. At about 500 images added, the Python process is using all about half of the volatile memory available. There are many more images than that.

How should I address this? I want the processing to complete and I don't mind if the processing takes a bit longer, but it would be good if I could limit the memory and CPU usage in some way. With the current approach, the machine becomes almost unusable while processing.

The code is as follows:

import os
import time
from   moviepy.editor import *

def ls_files(
    path = "."
    ):
    return([fileName for fileName in os.listdir(path) if os.path.isfile(
        os.path.join(path, fileName)
    )])

def main():

    listOfFiles = ls_files()
    listOfTileImageFiles = [fileName for fileName in listOfFiles \
        if "_tile.png" in fileName
    ]
    numberOfTiledImages = len(listOfTileImageFiles)

    # Create a video clip for each image.
    print("create video")
    videoClips = []
    imageDurations = []
    for imageNumber in range(0, numberOfTiledImages):
        imageFileName = str(imageNumber) + "_tile.png"
        print("add image {fileName}".format(
            fileName = imageFileName
        ))
        imageClip = ImageClip(imageFileName)
        duration  = 0.1
        videoClip = imageClip.set_duration(duration)
        # Determine the image start time by calculating the sum of the durations
        # of all previous images.
        if imageNumber != 0:
            videoStartTime = sum(imageDurations[0:imageNumber])
        else:
            videoStartTime = 0
        videoClip = videoClip.set_start(videoStartTime)
        videoClips.append(videoClip)
        imageDurations.append(duration)
    fullDuration = sum(imageDurations)
    video = concatenate(videoClips)
    video.write_videofile(
        "video.mp4",
        fps         = 30,
        codec       = "mpeg4",
        audio_codec = "libvorbis"
    )

if __name__ == "__main__":
    main()

Answer 1

If I understood correctly, you want to use the different images as the frames of your video.

In this case you should use ImageSequenceClip() (it's in the library, but not yet in the web docs, see here for the doc).

Basically, you just write

clip = ImageSequenceClip("some/directory/", fps=10)
clip.write_videofile("result.mp4")

And it will read the images in the directory in alpha-numerical order, while keeping only one frame at a time in the memory.

While I am at it, you can also provide a list of filenames or a list of numpy arrays to ImageSequenceClip.

Note that if you just want to transform images into a video, and not anything else fancy like adding titles or compositing with another video, then you can do it directly with ffmpeg. From memory the command should be:

ffmpeg -i *_tile.png -r 10 -o result.mp4