harvid decodes still images from movie files and serves them via HTTP.
harvid's intended use-case is to efficiently provide frame-accurate data and act as second level cache for rendering the video-timeline in Ardour, but it is not limited to that: it has applications for any task that requires a high-performance frame-accurate online image extraction processor.
The latest version is v0.8.2, released on Wed, 11 Jan 2017 10:58:58 +0100 (ChangeLog).
See the github repository page for source-code checkout options.
When used with Ardour, Ardour will automatically start the server when you open a video. You can also launch harvid manually. In either case it will by default listen for requests on http://localhost:1554/ and you can interact with it using any web-browser.
Please report bugs using the github issue tracker.