[FFmpeg-user] slideshow with crossfade

[Michael Koch]

I just figured out how to make a slideshow with crossfade. It's a two 
step process. The first step reads the pictures with framerate 0.5 
(which means 2 seconds for each picture), and produces an intermediate 
video with framerate 2. That means each picture is repeated 4 times. The 
second step applies the framerate filter. In the output video each 
picture is shown for 1.5 seconds, followed by a 0.5 second crossfade.

ffmpeg -framerate 0.5 -i IMG_%3d.jpg -r 2 -codec:v mpeg4 temp.mp4
ffmpeg -i temp.mp4 -vf "framerate=fps=25" -codec:v mpeg4 out.mp4

This two step process works fine, but I have two questions:
1. Is it also possible to get the same result in one step, without an 
intermediate video file?
2. If the answer to the first question is no, can someone please show me 
how the above commands must be modified for a lossless intermediate 
file, for example RAWVIDEO?

Thanks,
Michael