But Debian SID has been migrated to newer version of ffmpeg , and quite a lot of packages are depended on that version. Therefore, it is very trouble to rollback ffmpeg version to old one , which just to make OpenCV works.
In order to make Debian SID's OpenCV work with newer ffmpeg, I have submitted two patches for the issue. If you encounter similar problem like the one below, or OpenCV can not load AVI and image files. You probably need the patches:
Compiling an application and and then linking against libhighgui fails with:The bug report and patches