FFmpeg offers the overlay filter as a way to overlay images (or even other videos) onto video streams.

To centre overlay/watermark on a video, use this command:^[1]

ffmpeg -i inputvideo.avi -i watermarklogo.png -filter_complex \
"overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2" -codec:a copy output.flv

• -vf is used for simple filtergraphs (one input, one output), and -filter_complex is used for complex filtergraphs (one or more inputs, one or more outputs).
• Using -filter_complex will allow you omit the movie multimedia source filter and have a shorter command.
• The audio is simply stream copied (remuxed) in this example with -codec:a copy instead of being re-encoded. You may have to re-encode depending on your output container format.
• See the documentation on the overlay video filter for more information and examples. For example, you could use aliases to shorten the command: overlay=(W-w)/2:(H-h)/2
• See the FFmpeg H.264 Video Encoding Guide for more information on getting a good quality output.

References