Convert single png file to mp4

Question

I'm trying to find a way to convert a single png image to an mp4 file with a specified length. Solutions I have found are slow and unreliable when trying to make videos with longer lengths (multiple hours).

Here is my current solution in Python 3:

import os
import cv2

video_name = 'video.avi'
frame = cv2.imread('image.png')
height, width, layers = frame.shape

time = 300
    
video = cv2.VideoWriter(video_name, 0, 1 / 10, (width,height))

for i in range(int(time / 10)):
    video.write(cv2.imread(os.path.join('.', 'image.png')))

video.write(cv2.imread('image.png'))

cv2.destroyAllWindows()
video.release()

Basically the same image is appended multiple times to make up the video, and I found that it was very taxing to merge so therefore the fps is set to 0.1 seconds.

This feels like the wrong approach so any solutions are appreciated

Answer 1

you'll like PyAV. it's a proper wrapper around ffmpeg's libraries, not the usual subprocess kludges you find in random python packages.

it has a sample where frames are written with custom Presentation Timestamps instead of a fixed frame rate. the math/usage is a little nebulous thanks to ffmpeg not making those things clear in their own documentation.

basically you set av.VideoFrame.pts and that's it.

https://github.com/PyAV-Org/PyAV/blob/main/examples/numpy/generate_video_with_pts.py

do understand that video with unusually long times between frames may be a challenge for some video players, at least when trying to seek instead of playing sequentially.

OpenCV is not a media library. its video I/O functions are intended and designed to be convenient and not flexible.