`ffmpeg` added some range checking to all filter parameters which are of type duration. One such example is (strangely enough) the `start_time`/`st` parameter of the `fade` filter. In our system, this parameter can become negative, if the fade duration is longer than the faded clip itself; the start time of the fade out will then become negative.
I have a fix for that particular case, but there might be more places where this is important.
Currently this stops Opencast from building on systems with newer `ffmpeg`-s, because of a failing test, in which the situation described above comes up. (`org.opencastProject.composer.impl.ProcessSmilTest#testProcessSmilMultiSegment` in `composer-ffmpeg`)