Android get online video file and extract thumbnail

I am trying to get a video that is stored on Amazons S3 (I have a public link to a .mp4 file) and extract a thumbnail from the first frame of the video.

There are questions here on how to do this, but target local files or Youtube files.

Does anyone have an example of this but is targeting an online file?

I'm trying to use the MediaMetadataRetriever class, but I can't seem to get it to work.

thank