Gapless audio in video It's possible to produce mp4/webm videos without sound that loop seamlessly, but if you add sound to the video with matching length it adds a noticeable stutter at the end, even if the audio is slightly shorter than the video.

Is it possible to produce a web friendly (mp4/webm) video with sound that is gapless?

I use Adobe products and ffmpeg to produce my videos, if that matters.
This can happen if the GOP structure is unclosed at the end of the video. If you can assure that your video ends with an I frame, and that the audio is exactly the same length as the video, you stand a much better chance of getting a smooth recycle. Sorry, I don't know how to force that using ffmpeg.