How do I add a custom thumbnail to a .mp4 file using ffmpeg?

I am trying to find the proper ffmpeg command to add a .png or .jpg image to a .mp4 video as a thumbnail. The command will eventually automatically be executed by a C# program.

This is what I have so far:

# This does not work. It only removes the default thumbnail.
ffmpeg -i video.mp4 -i image.png -acodec copy -vcodec copy -map 0 -map 1:0 OUTPUT.mp4

Is what I want possible with ffmpeg? If so, please guide me in the right direction.

Solution 1:

Using ffmpeg 4.0, released Apr 20 2018 or newer,

ffmpeg -i video.mp4 -i image.png -map 1 -map 0 -c copy -disposition:0 attached_pic out.mp4

Solution 2:

As in version 4.2.2...See Section 5.4 in FFmpeg documentation

To add an embedded cover/thumbnail:

ffmpeg -i in.mp4 -i IMAGE -map 0 -map 1 -c copy -c:v:1 png -disposition:v:1 attached_pic out.mp4

Not all muxers support embedded thumbnails, and those who do, only support a few formats, like JPEG or PNG.