[FFmpeg-devel] Correct use of zoompan filter in combination with other filters.

[Ryan Williams]

Hoping a developer can enlighten me as to why I'm having problems chaining
the zoompan filter to the overlay filter.

When I take a single jpg, feed it into zoompan and conjure 250 frames of
output it works fine.
But when I attempt to take those 250 frames and use them as an input to the
overlay filter I get dropped frames during the encoding process.


I posted this on the users list but didn't get a response.
http://ffmpeg.org/pipermail/ffmpeg-user/2015-December/029508.html

I suspect this has something to do with the zoompan filter outputting more
frames than it consumed as I've also encountered this problem when using the
fps filter to increase the framerate.

I can work around this problem by using intermediate files, named pipes or
the 'fifo' filter but I'd love to know is there something I'm missing or at
the least a little more understanding of why this problem occurs.