Thank you for your quick reply.
c:\ProgramData\Anaconda3\python.exe c:\ProgramData\Anaconda3\lib\site-packages\sfepy\script\postproc.py c:\ProgramData\Anaconda3\Scripts\NOTEBOOKS\cylinder.00.vtk c:\ProgramData\Anaconda3\Scripts\NOTEBOOKS\cylinder.01.vtk
did the trick. It was, in deed, a problem with the wildcards expansion (specific to windows ?)
ffmpeg works after renaming the files view.x_0_00000e+00.png to view-x.png .
Thank you very much.