[FFmpeg-user] Grab stills on scene change math question

[Bouke (VideoToolShed)]

Hi all,
Trying to grab images from each scene.
Now I'm using:
ffmpeg -i input.mxf -vf select="gt(scene\,0.4),scale=320:240" -vsync 0 
thumb%03d.png
And that works brilliant.

But now I also want to grab stills from the last frame of a shot.
So I thought that perhaps this would work:
select="(gt(scene\,0.4)-1),scale=320:240"
assuming that gt(scene\,0.4) will return a number that I could do math on, 
but this fails.

Is something like this possible?
And to make it more complex, can I also grab a shot out of the middle of a 
scene?
(that would require to get the current and next framenumber, subtract and 
divide by two to an integer and add to the first...)

thx,
Bouke 


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