ffmepg video from uneven sequence of png images

I'm going to make a video from series of screenshots (.png files). For each screenshot there is assosiated timestamp information about when it was taken. The time intervals between screenshots may vary and it's highly desired to preserve that difference in the video.

Is there a way to use single ffmpeg command/API providing to it sequence of image + time (or frame) offset and getting one video file as output? By now I have to generate short video files of custom length for each image, and then merge them manually:

ffmpeg -y -loop 1 -i image1.png -c:v libx264 -t 1.52 video1.avi
ffmpeg -y -loop 1 -i image2.png -c:v libx264 -t 2.28 video2.avi
...
ffmpeg -y -loop 1 -i imageN.png -c:v libx264 -t 1.04 videoN.avi


ffmpeg -i "concat:video1.avi|video2.avi|...videoN.avi" -c copy output.avi

This is quite ok, while intervals are large, but the whole approach seems to me a bit fragile.

Solution

Use the concat demuxer.

enter image description here
_{Example using 2, 4, and 0.25 seconds.}

Make a text file indicating the desired duration per file:
```
file 'image1.png'
duration 1.52
file 'image2.png'
duration 2.28
file 'image3.png'
duration 1.04
```
You may have to repeat the last file and duration lines to get it to display the last frame.

Run the ffmpeg command:

ffmpeg -f concat -i input.txt -c:v libx264 -pix_fmt yuv420p -movflags +faststart output.mp4