Yes , The ffmpeg argument is wrong ...
Is like this;
{ time ffmpeg -t 60 -i ./video -r 7 -f image2pipe -vcodec bmp - | mkbitmap -x -f 3.5 -s 1 -b 1 -t 0.48 -o - | potrace --alphamax 1.334 --turdsize 2 --longcurve --turnpolicy black -b pdf -o ./pdf-file-output.pdf }
Please if you could ! test it , let me know the fps and time .