ffmpeg has been able to record a screencast on X11 for a long time now, using the x11grab input format and the :0.0 device (for the first instance of X). You’d run
ffmpeg -f x11grab -y -r 12 -s 800x600 -i :0.0+480,200 -vcodec ffv1 -sameq ./out.avi
and get a lossless video of the upper right 800×600 area of a 1280×800 desktop. Easy. You could even transcode to a lossy format (such as H.264, Xvid or Theora) if you had a powerful machine.
On Windows it was not that easy. First of all, Windows is not X11, so x11grab does not work on Windows. You need to use GDI or DirectX but ffmpeg did not have support for GDI or DirectX capture. If you wanted screen-grabbing features in you application, either you developed your own solution (ugly, specially because of the video encoding part) or you used Camtasia Studio (Wink does not include a DLL or ActiveX component you can use in your app).
Ramiro Polla and Christophe Gisquet had a heated discussion about one and a half years ago and some very interesting code was shown. Unfortunately, neither Ramiro’s nor Christophe’s code would work with current ffmpeg.
Today I’ve finally brought Ramiro’s code up to date and it works with ffmpeg trunk. It is not perfect, though: it does not capture the mouse pointer, contextual menus shown as a result of a right-click and video scaling and color is not perfect (ffplay shows the video a little blue-ish). Patch. I’ll try and bring Christophe’s code up to date tomorrow, or fix Ramiro’s code.
PS: A request for ffmpeg developers: please, replace your custom configure script with some cross-platform build system. I like CMake but Scons, Waf and others would also do.