[FFmpeg-user] Using expressions in "FADE" filter

Moritz Barsnick barsnick at gmx.net
Thu Apr 30 19:18:00 CEST 2015

[Your responses are backwards. That makes reading ... awkward.]

On Thu, Apr 30, 2015 at 12:33:34 -0400, Shlomo Morosow wrote:

> > https://www.ffmpeg.org/ffmpeg-utils.html#Expression-Evaluation

Where does it say that epressions are expressed as such?
  "%{expr\\\: (10-1)}"

> > I regularly use this in many filters and it works just as expected, it's
> > just that I ran into an issue with the fade filter.

_Please_ show me a working example with your syntax! You don't have to
provide a file, you can do
$ ffmpeg -f lavfi -i testsrc -t 10 [...] -vf "your filter with expression here" -f null -

As I think I mentioned: Only filters' arguments designed to use
expressions will actually use them. And I still don't see the point of
expressing "frames (or seconds) from the end", how do you plan to tell
the expression what the end of the video is?

Please help!


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