One of the recent development themes for the Mir display server project was wiring up screencasting support. That basic support has been in place for casting an entire Mir screen using the mirscreencast utility but now it's a little bit better.
The Mir Screencast implementation now supports screencasting a region of the screen and capturing at a user-supplied size. This work via Mir's revision 1465 allows for capturing at a lower resolution to improve the casting performance or for just capturing a smaller portion of the screen. With a follow-up change new options were added to the Mir Screencast utility to specify an output filename, directing output to stdout so the screen contents can be piped to other utilities, customizing the screencast size, and specifying a screen region to capture. These changes will be useful for those wanting to capture all/part of their screen and then dumping the cast into FFmpeg or a similar utility.
In other recent Mir work, there's another change that can make additional resizing modes possible along with improving some resize logic and adding support for Android's HWC overlay layers. A few days prior, Mir's demo shell got its own custom renderer.