MJPEG is so freaking simple [1] and almost no one knows about it. It's one of my favorite things to play around with and in my opinion way underutilized.
I built "drawing board" a while ago using an old school image map streaming a motion jpeg. You can interact with the video without ANY JavaScript [2]. The browser stays where you are on posting because the server returns an HTTP 204 - also highly underutilized in my opinion.
MJPEG in casual parlance is more of a "technique" than a format -- and multipart/x-mixed-replace is a very loose definition of even something as loosely defined as MJPEG.
Out of video containers, QuickTime introduced "Motion-JPEG" [1] with each frame in the container being a JPEG, and there have been formal definitions of how to communicate "JPEG-compressed video" with network protocols, like in RTP [2].
Meanwhile mixed-replace was a Netscape trick [3] to do server push with HTTP that never became a real force but was reimplemented by almost every browser trying to stay Mozilla-compatible (except IE), and happily used by webcams for dead-simple videostreaming.
I built "drawing board" a while ago using an old school image map streaming a motion jpeg. You can interact with the video without ANY JavaScript [2]. The browser stays where you are on posting because the server returns an HTTP 204 - also highly underutilized in my opinion.
1. https://github.com/donatj/mjpeg-php/blob/master/mjpeg.php
2. https://github.com/donatj/imgboard