ffmpeg convert variable framerate movie to pics

is it possible to use ffmpeg to convert a movie with variable framerate to a sequence of still pics without duplicates? I tried something like:

ffmpeg -i vid.avi pic%d.png

but each frame generates thousands of pictures. I also tried:

ffmpeg 开发者_运维问答-i vid.avi -r 10 pic%d.png

but I still have lots of duplicates AND some frames are missing

is it possible to specify something like "-r natural"???

TIA

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A bit late, but...

ffmpeg -vsync 2 -i <input movie> <output with %d>

will do the trick. For example:

ffmpeg -vsync 2 -i "C:\Test.mp4" "C:\Thumbnails\Test%d.jpg"

will create exactly one jpeg per frame in the C:\Thumbnails folder, and each jpeg will be sequentially numbered with no gaps or duplicates in numbering.