ffmpeg wrapper starts an ffmpeg process and hooks the WM_CLOSE event sent by windows when a taskkilll command is sent to the wrapper's process. The wrapper then shuts down the child ffmpeg process it started gracefully to avoid file corruption issues.
This is meant to be shipped alongside ffmpeg in cases where the only way to tell ffmpeg to shut down gracefully is to send a taskkill command(ffmpeg is being used by host software that needs to interrupt ffmpeg). ffmpeg doesn't run with a window handle unless you specifically give ffmpeg a window handle using the start command. This still doesn't fix the fact that ffmpeg is not designed to handle this edge case. ffmpeg doesn't handle any WM_CLOSE event, so assigning a window handle isn't enough.
Don't use the /F option or the WM_CLOSE event isn't fired and the wrapper will fail to shut down ffmpeg gracefully.
ffmpeg_wrap is written with nim. You need wnim and winim if you want to compile ffmpeg_wrap. You can use nimble to get both.
nimble install winim
nimble install wnim
The resulting binary is around 1.5mb, but if you compile with the --opt:size flag it's less than 700kb
This will record a section of your screen until you run taskkill /PID FFMPEG_WRAPPER_PID
ffmpeg_wrap.exe ffmpeg.exe -rtbufsize 150M -f gdigrab -framerate 30 -offset_x 448 -offset_y 240 -video_size 1024x600 -draw_mouse 1 -show_region 1 -i desktop -r 30 -preset ultrafast -tune zerolatency -movflags +faststart screen-recording.mp4