in vvvv it is very easy to edit HLSL shaders and apply the changes during runtime. but for the scenario of opening a video file, preocess it and save it again there is no ready made solution. you can however process image sequences very easily.
so you could do a workaround like this: convert video with a video editor of your choice to an image sequence and one audio file. then process the frames and join the processed frames with the audio file back together with a video editor.
You could use file stream, and use DoSeek pin and set the time position per frame, for the input, so you don’t need to work on a file sequence, but there is no non realtime file writer, so you would have to export to image sequence and recombine with the audio afterwards.
(a non real time video writer, would be wonderful, but sadly missing)