How do I playout rtmp stream to SDI (Decklink Studio 4K) using FFMPEG command?we are using Windows 7 operating system
As the docs say,


  you need the Blackmagic DeckLink SDK and you need to configure with
  the appropriate --extra-cflags and --extra-ldflags. On Windows, you
  need to run the IDL files through widl


If so, run

ffmpeg -re -i rtmp://server/live/streamname -c:v rawvideo -pix_fmt uyvy422 -vf scale=720x576 -c:a pcm_s16le -ar 48000 -ac 2 -f decklink "Device"


where Device is to replaced with the name of 'Decklink Studio 4K' as indicated by ffmpeg -f lavfi -i nullsrc -f decklink -list_devices 1 dummy