Fix compilation error when buildng with FFMPEG (#27589)
Summary:
When building with FFMPEG, I encountered compilation error due to missing include/library.
I also find the change in video_input_op.h will improve build on Windows.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27589
Differential Revision: D19700351
Pulled By: ezyang
fbshipit-source-id: feff25daa43bd2234d5e75c66b9865b672a8fb51
