Currently DirectShowSource() can open variable
framerate source as long as the "fps" parameter is
However, the timestamps in the video frames are not
taken into account and the frames are assumed of fixed
rate - whereas they are not.
I suggest a new parameter that would cause
DirectShowSource() to examine the timestamps in the
video frames and add or remove frames as needed to
produce a real fixed rate video stream of a rate as
specified by the parameter fps.
This would allow AviSynth to work on sources that have
a variable frame rate without causing audio/video